Don't abort startup when setgid/setuid() fails with EINVAL

[ngircd-alex.git] / src / ngircd / conn.c

/*
 * ngIRCd -- The Next Generation IRC Daemon
 * Copyright (c)2001-2024 Alexander Barton (alex@barton.de) and Contributors.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * Please read the file COPYING, README and AUTHORS for more information.
 */

#define CONN_MODULE
#define CONN_MODULE_GLOBAL_INIT

#include "portab.h"

/**
 * @file
 * Connection management
 */

/* Additionan debug messages related to buffer handling: 0=off / 1=on */
#define DEBUG_BUFFER 0

#include <assert.h>
#ifdef PROTOTYPES
# include <stdarg.h>
#else
# include <varargs.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <strings.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <netinet/in.h>

#ifdef HAVE_NETINET_IP_H
# ifdef HAVE_NETINET_IN_SYSTM_H
#  include <netinet/in_systm.h>
# endif
# include <netinet/ip.h>
#endif

#ifdef TCPWRAP
# include <tcpd.h>                      /* for TCP Wrappers */
#endif

#include "conn.h"

#include "ngircd.h"
#include "class.h"
#ifdef ICONV
# include "conn-encoding.h"
#endif
#include "conn-ssl.h"
#include "conn-zip.h"
#include "conn-func.h"
#include "io.h"
#include "log.h"
#include "ng_ipaddr.h"
#include "parse.h"
#include "resolve.h"
#include "sighandlers.h"

#define SERVER_WAIT (NONE - 1)          /** "Wait for outgoing connection" flag */

#define MAX_COMMANDS 3                  /** Max. commands per loop for users */
#define MAX_COMMANDS_SERVER_MIN 10      /** Min. commands per loop for servers */
#define MAX_COMMANDS_SERVICE 10         /** Max. commands per loop for services */

#define SD_LISTEN_FDS_START 3           /** systemd(8) socket activation offset */

#define THROTTLE_CMDS 1                 /** Throttling: max commands reached */
#define THROTTLE_BPS 2                  /** Throttling: max bps reached */

static bool Handle_Write PARAMS(( CONN_ID Idx ));
static bool Conn_Write PARAMS(( CONN_ID Idx, char *Data, size_t Len ));
static int New_Connection PARAMS(( int Sock, bool IsSSL ));
static CONN_ID Socket2Index PARAMS(( int Sock ));
static void Read_Request PARAMS(( CONN_ID Idx ));
static unsigned int Handle_Buffer PARAMS(( CONN_ID Idx ));
static void Check_Connections PARAMS(( void ));
static void Check_Servers PARAMS(( void ));
static void Init_Conn_Struct PARAMS(( CONN_ID Idx ));
static bool Init_Socket PARAMS(( int Sock ));
static void New_Server PARAMS(( int Server, ng_ipaddr_t *dest ));
static void Simple_Message PARAMS(( int Sock, const char *Msg ));
static int NewListener PARAMS(( const char *listen_addr, UINT16 Port ));
static void Account_Connection PARAMS((void));
static void Throttle_Connection PARAMS((const CONN_ID Idx, CLIENT *Client,
                                        const int Reason, unsigned int Value));

static array My_Listeners;
static array My_ConnArray;
static size_t NumConnections, NumConnectionsMax, NumConnectionsAccepted;

#ifdef TCPWRAP
int allow_severity = LOG_INFO;
int deny_severity = LOG_ERR;
#endif

static void server_login PARAMS((CONN_ID idx));

#ifdef SSL_SUPPORT
extern struct SSLOptions Conf_SSLOptions;
static bool SSL_WantRead PARAMS((const CONNECTION *c));
static bool SSL_WantWrite PARAMS((const CONNECTION *c));
static void cb_listen_ssl PARAMS((int sock, short irrelevant));
static void cb_connserver_login_ssl PARAMS((int sock, short what));
static void cb_clientserver_ssl PARAMS((int sock, short what));
#endif
static void cb_Read_Resolver_Result PARAMS((int sock, UNUSED short what));
static void cb_Connect_to_Server PARAMS((int sock, UNUSED short what));
static void cb_clientserver PARAMS((int sock, short what));

time_t idle_t = 0;

/**
 * Get number of sockets available from systemd(8).
 *
 * ngIRCd needs to implement its own sd_listen_fds(3) function and can't
 * use the one provided by systemd itself, because the sockets will be
 * used in a forked child process with a new PID, and this would trigger
 * an error in the standard implementation.
 *
 * @return Number of sockets available, -1 if sockets have already been
 *         initialized, or 0 when no sockets have been passed.
 */
static int
my_sd_listen_fds(void)
{
        const char *e;
        int count;

        /* Check if LISTEN_PID exists; but we ignore the result, because
         * normally ngircd forks a child before checking this, and therefore
         * the PID set in the environment is always wrong ... */
        e = getenv("LISTEN_PID");
        if (!e || !*e)
                return 0;

        e = getenv("LISTEN_FDS");
        if (!e || !*e)
                return -1;
        count = atoi(e);
#ifdef HAVE_UNSETENV
        unsetenv("LISTEN_FDS");
#endif

        return count;
}

/**
 * IO callback for listening sockets: handle new connections. This callback
 * gets called when a new non-SSL connection should be accepted.
 *
 * @param sock          Socket descriptor.
 * @param irrelevant    (ignored IO specification)
 */
static void
cb_listen(int sock, short irrelevant)
{
        (void) irrelevant;
        (void) New_Connection(sock, false);
}

/**
 * IO callback for new outgoing non-SSL server connections.
 *
 * @param sock  Socket descriptor.
 * @param what  IO specification (IO_WANTREAD/IO_WANTWRITE/...).
 */
static void
cb_connserver(int sock, UNUSED short what)
{
        int res, err, server;
        socklen_t sock_len;
        CONN_ID idx = Socket2Index( sock );

        if (idx <= NONE) {
                io_close(sock);
                return;
        }

        assert(what & IO_WANTWRITE);

        /* Make sure that the server is still configured; it could have been
         * removed in the meantime! */
        server = Conf_GetServer(idx);
        if (server < 0) {
                Log(LOG_ERR, "Connection on socket %d to \"%s\" aborted!",
                    sock, My_Connections[idx].host);
                Conn_Close(idx, "Connection aborted", NULL, false);
                return;
        }

        /* connect() finished, get result. */
        sock_len = (socklen_t)sizeof(err);
        res = getsockopt(My_Connections[idx].sock, SOL_SOCKET, SO_ERROR,
                         &err, &sock_len );
        assert(sock_len == sizeof(err));

        /* Error while connecting? */
        if ((res != 0) || (err != 0)) {
                if (res != 0)
                        Log(LOG_CRIT, "getsockopt (connection %d): %s!",
                            idx, strerror(errno));
                else
                        Log(LOG_CRIT,
                            "Can't connect socket to \"%s:%d\" (connection %d): %s!",
                            My_Connections[idx].host, Conf_Server[server].port,
                            idx, strerror(err));

                Conn_Close(idx, "Can't connect", NULL, false);

                if (ng_ipaddr_af(&Conf_Server[server].dst_addr[0])) {
                        /* more addresses to try... */
                        New_Server(server, &Conf_Server[server].dst_addr[0]);
                        /* connection to dst_addr[0] is now in progress, so
                         * remove this address... */
                        Conf_Server[server].dst_addr[0] =
                                Conf_Server[server].dst_addr[1];
                        memset(&Conf_Server[server].dst_addr[1], 0,
                               sizeof(Conf_Server[server].dst_addr[1]));
                }
                return;
        }

        /* connect() succeeded, remove all additional addresses */
        memset(&Conf_Server[server].dst_addr, 0,
               sizeof(Conf_Server[server].dst_addr));

        Conn_OPTION_DEL( &My_Connections[idx], CONN_ISCONNECTING );
#ifdef SSL_SUPPORT
        if ( Conn_OPTION_ISSET( &My_Connections[idx], CONN_SSL_CONNECT )) {
                io_event_setcb( sock, cb_connserver_login_ssl );
                io_event_add( sock, IO_WANTWRITE|IO_WANTREAD );
                return;
        }
#endif
        server_login(idx);
}

/**
 * Login to a remote server.
 *
 * @param idx   Connection index.
 */
static void
server_login(CONN_ID idx)
{
        Log(LOG_INFO,
            "Connection %d (socket %d) with \"%s:%d\" established. Now logging in ...",
            idx, My_Connections[idx].sock, My_Connections[idx].host,
            Conf_Server[Conf_GetServer(idx)].port);

        io_event_setcb( My_Connections[idx].sock, cb_clientserver);
        io_event_add( My_Connections[idx].sock, IO_WANTREAD|IO_WANTWRITE);

        /* Send PASS and SERVER command to peer */
        Conn_WriteStr(idx, "PASS %s %s",
                      Conf_Server[Conf_GetServer( idx )].pwd_out, NGIRCd_ProtoID);
        Conn_WriteStr(idx, "SERVER %s :%s",
                      Conf_ServerName, Conf_ServerInfo);
}

/**
 * IO callback for established non-SSL client and server connections.
 *
 * @param sock  Socket descriptor.
 * @param what  IO specification (IO_WANTREAD/IO_WANTWRITE/...).
 */
static void
cb_clientserver(int sock, short what)
{
        CONN_ID idx = Socket2Index(sock);

        if (idx <= NONE) {
                io_close(sock);
                return;
        }

#ifdef SSL_SUPPORT
        if (what & IO_WANTREAD
            || (Conn_OPTION_ISSET(&My_Connections[idx], CONN_SSL_WANT_WRITE))) {
                /* if TLS layer needs to write additional data, call
                 * Read_Request() instead so that SSL/TLS can continue */
                Read_Request(idx);
        }
#else
        if (what & IO_WANTREAD)
                Read_Request(idx);
#endif
        if (what & IO_WANTWRITE)
                Handle_Write(idx);
}

/**
 * Initialize connection module.
 */
GLOBAL void
Conn_Init( void )
{
        int size;

        /* Initialize the "connection pool".
         * FIXME: My_Connetions/Pool_Size is needed by other parts of the
         * code; remove them! */
        Pool_Size = 0;
        size = Conf_MaxConnections > 0 ? Conf_MaxConnections : CONNECTION_POOL;
        if (Socket2Index(size) <= NONE) {
                Log(LOG_EMERG, "Failed to initialize connection pool!");
                exit(1);
        }

        /* Initialize "listener" array. */
        array_free( &My_Listeners );
} /* Conn_Init */

/**
 * Clean up connection module.
 */
GLOBAL void
Conn_Exit( void )
{
        CONN_ID idx;

        Conn_ExitListeners();

        LogDebug("Shutting down all connections ..." );
        for( idx = 0; idx < Pool_Size; idx++ ) {
                if( My_Connections[idx].sock > NONE ) {
                        Conn_Close( idx, NULL, NGIRCd_SignalRestart ?
                                "Server going down (restarting)":"Server going down", true );
                }
        }

        array_free(&My_ConnArray);
        My_Connections = NULL;
        Pool_Size = 0;
        io_library_shutdown();
} /* Conn_Exit */

/**
 * Close all sockets (file descriptors) of open connections.
 * This is useful in forked child processes, for example, to make sure that
 * they don't hold connections open that the main process wants to close.
 */
GLOBAL void
Conn_CloseAllSockets(int ExceptOf)
{
        CONN_ID idx;

        for(idx = 0; idx < Pool_Size; idx++) {
                if(My_Connections[idx].sock > NONE &&
                   My_Connections[idx].sock != ExceptOf)
                        close(My_Connections[idx].sock);
        }
}

/**
 * Initialize listening ports.
 *
 * @param a             Array containing the ports the daemon should listen on.
 * @param listen_addr   Address the socket should listen on (can be "0.0.0.0").
 * @param func          IO callback function to register.
 * @returns             Number of listening sockets created.
 */
static unsigned int
Init_Listeners(array *a, const char *listen_addr, void (*func)(int,short))
{
        unsigned int created = 0;
        size_t len;
        int fd;
        UINT16 *port;

        len = array_length(a, sizeof (UINT16));
        port = array_start(a);
        while (len--) {
                fd = NewListener(listen_addr, *port);
                if (fd < 0) {
                        port++;
                        continue;
                }
                if (!io_event_create( fd, IO_WANTREAD, func )) {
                        Log(LOG_ERR,
                            "io_event_create(): Can't add fd %d (port %u): %s!",
                            fd, (unsigned int) *port, strerror(errno));
                        close(fd);
                        port++;
                        continue;
                }
                created++;
                port++;
        }
        return created;
}

/**
 * Initialize all listening sockets.
 *
 * @returns     Number of created listening sockets
 */
GLOBAL unsigned int
Conn_InitListeners( void )
{
        /* Initialize ports on which the server should accept connections */
        unsigned int created = 0;
        char *af_str, *copy, *listen_addr;
        int count, fd, i, addr_len;
        ng_ipaddr_t addr;

        assert(Conf_ListenAddress);

        count = my_sd_listen_fds();
        if (count < 0) {
                Log(LOG_INFO,
                    "Not re-initializing listening sockets of systemd(8) ...");
                return 0;
        }
        if (count > 0) {
                /* systemd(8) passed sockets to us, so don't try to initialize
                 * listening sockets on our own but use the passed ones */
                LogDebug("Initializing %d systemd sockets ...", count);
                for (i = 0; i < count; i++) {
                        fd = SD_LISTEN_FDS_START + i;
                        addr_len = (int)sizeof(addr);
                        getsockname(fd, (struct sockaddr *)&addr,
                                    (socklen_t*)&addr_len);
#ifdef WANT_IPV6
                        if (addr.sin4.sin_family != AF_INET
                            && addr.sin4.sin_family != AF_INET6)
#else
                        if (addr.sin4.sin_family != AF_INET)
#endif
                        {
                                /* Socket is of unsupported type! For example,
                                 * systemd passed in an IPv6 socket but ngIRCd
                                 * isn't compiled with IPv6 support. */
                                switch (addr.sin4.sin_family)
                                {
                                        case AF_UNSPEC: af_str = "AF_UNSPEC"; break;
                                        case AF_UNIX: af_str = "AF_UNIX"; break;
                                        case AF_INET: af_str = "AF_INET"; break;
#ifdef AF_INET6
                                        case AF_INET6: af_str = "AF_INET6"; break;
#endif
#ifdef AF_NETLINK
                                        case AF_NETLINK: af_str = "AF_NETLINK"; break;
#endif
                                        default: af_str = "unknown"; break;
                                }
                                Log(LOG_CRIT,
                                    "Socket %d is of unsupported type \"%s\" (%d), have to ignore it!",
                                    fd, af_str, addr.sin4.sin_family);
                                close(fd);
                                continue;
                        }

                        Init_Socket(fd);
                        if (!io_event_create(fd, IO_WANTREAD, cb_listen)) {
                                Log(LOG_ERR,
                                    "io_event_create(): Can't add fd %d: %s!",
                                    fd, strerror(errno));
                                continue;
                        }
                        Log(LOG_INFO,
                            "Initialized socket %d from systemd(8): %s:%d.", fd,
                            ng_ipaddr_tostr(&addr), ng_ipaddr_getport(&addr));
                        created++;
                }
                return created;
        }

        /* not using systemd socket activation, initialize listening sockets: */

#ifdef SSL_SUPPORT
        if (!Conf_SSLOptions.KeyFile &&
            array_length(&Conf_SSLOptions.ListenPorts, sizeof (UINT16))) {
                Log(LOG_ERR,
                    "Ignoring SSL-enabled listening ports: No key file set!");
                array_free(&Conf_SSLOptions.ListenPorts);
        }
#endif

        /* can't use Conf_ListenAddress directly, see below */
        copy = strdup(Conf_ListenAddress);
        if (!copy) {
                Log(LOG_CRIT, "Cannot copy %s: %s", Conf_ListenAddress,
                    strerror(errno));
                return 0;
        }
        listen_addr = strtok(copy, ",");

        while (listen_addr) {
                ngt_TrimStr(listen_addr);
                if (*listen_addr) {
                        created += Init_Listeners(&Conf_ListenPorts,
                                                  listen_addr, cb_listen);
#ifdef SSL_SUPPORT
                        created += Init_Listeners(&Conf_SSLOptions.ListenPorts,
                                                  listen_addr, cb_listen_ssl);
#endif
                }

                listen_addr = strtok(NULL, ",");
        }

        /* Can't free() Conf_ListenAddress here: on REHASH, if the config file
         * cannot be re-loaded, we'd end up with a NULL Conf_ListenAddress.
         * Instead, free() takes place in conf.c, before the config file
         * is being parsed. */
        free(copy);

        return created;
} /* Conn_InitListeners */

/**
 * Shut down all listening sockets.
 */
GLOBAL void
Conn_ExitListeners( void )
{
        /* Close down all listening sockets */
        int *fd;
        size_t arraylen;

        /* Get number of listening sockets to shut down. There can be none
         * if ngIRCd has been "socket activated" by systemd. */
        arraylen = array_length(&My_Listeners, sizeof (int));
        if (arraylen < 1)
                return;

        Log(LOG_INFO,
            "Shutting down all listening sockets (%d total) ...", arraylen);
        fd = array_start(&My_Listeners);
        while(arraylen--) {
                assert(fd != NULL);
                assert(*fd >= 0);
                io_close(*fd);
                LogDebug("Listening socket %d closed.", *fd );
                fd++;
        }
        array_free(&My_Listeners);
} /* Conn_ExitListeners */

/**
 * Bind a socket to a specific (source) address.
 *
 * @param addr                  Address structure.
 * @param listen_addrstr        Source address as string.
 * @param Port                  Port number.
 * @returns                     true on success, false otherwise.
 */
static bool
InitSinaddrListenAddr(ng_ipaddr_t *addr, const char *listen_addrstr, UINT16 Port)
{
        bool ret;

        ret = ng_ipaddr_init(addr, listen_addrstr, Port);
        if (!ret) {
                assert(listen_addrstr);
                Log(LOG_CRIT,
                    "Can't listen on [%s]:%u: Failed to parse IP address!",
                    listen_addrstr, Port);
        }
        return ret;
}

/**
 * Set a socket to "IPv6 only". If the given socket doesn't belong to the
 * AF_INET6 family, or the operating system doesn't support this functionality,
 * this function returns silently.
 *
 * @param af    Address family of the socket.
 * @param sock  Socket handle.
 */
static void
set_v6_only(int af, int sock)
{
#if defined(IPV6_V6ONLY) && defined(WANT_IPV6)
        int on = 1;

        if (af != AF_INET6)
                return;

        if (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &on, (socklen_t)sizeof(on)))
                Log(LOG_ERR, "Could not set IPV6_V6ONLY: %s", strerror(errno));
#else
        (void)af;
        (void)sock;
#endif
}

/**
 * Initialize new listening port.
 *
 * @param listen_addr   Local address to bind the socket to (can be 0.0.0.0).
 * @param Port          Port number on which the new socket should be listening.
 * @returns             file descriptor of the socket or -1 on failure.
 */
static int
NewListener(const char *listen_addr, UINT16 Port)
{
        /* Create new listening socket on specified port */
        ng_ipaddr_t addr;
        int sock, af;

        if (!InitSinaddrListenAddr(&addr, listen_addr, Port))
                return -1;

        af = ng_ipaddr_af(&addr);
        sock = socket(af, SOCK_STREAM, 0);
        if (sock < 0) {
                Log(LOG_CRIT, "Can't create socket (af %d) : %s!", af,
                    strerror(errno));
                return -1;
        }

        set_v6_only(af, sock);

        if (!Init_Socket(sock))
                return -1;

        if (bind(sock, (struct sockaddr *)&addr, ng_ipaddr_salen(&addr)) != 0) {
                Log(LOG_CRIT, "Can't bind socket to address %s:%d - %s!",
                    ng_ipaddr_tostr(&addr), Port, strerror(errno));
                close(sock);
                return -1;
        }

        if (listen(sock, 10) != 0) {
                Log(LOG_CRIT, "Can't listen on socket: %s!", strerror(errno));
                close(sock);
                return -1;
        }

        /* keep fd in list so we can close it when ngircd restarts/shuts down */
        if (!array_catb(&My_Listeners, (char *)&sock, sizeof(int))) {
                Log(LOG_CRIT, "Can't add socket to My_Listeners array: %s!",
                    strerror(errno));
                close(sock);
                return -1;
        }

        Log(LOG_INFO, "Now listening on [%s]:%d (socket %d).",
            ng_ipaddr_tostr(&addr), Port, sock);
        return sock;
} /* NewListener */

/**
 * "Main Loop": Loop until shutdown or restart is signalled.
 *
 * This function loops until a shutdown or restart of ngIRCd is signalled and
 * calls io_dispatch() to check for readable and writable sockets every second.
 * It checks for status changes on pending connections (e. g. when a hostname
 * has been resolved), checks for "penalties" and timeouts, and handles the
 * input buffers.
 */
GLOBAL void
Conn_Handler(void)
{
        int i;
        size_t wdatalen;
        struct timeval tv;
        time_t t, notify_t = 0;
        bool command_available;
        char status[200];

        Log(LOG_NOTICE, "Server \"%s\" (on \"%s\") ready.",
            Client_ID(Client_ThisServer()), Client_Hostname(Client_ThisServer()));
        Signal_NotifySvcMgr("READY=1\n");

        while (!NGIRCd_SignalQuit && !NGIRCd_SignalRestart) {
                t = time(NULL);
                command_available = false;

                /* Check configured servers and established links */
                Check_Servers();
                Check_Connections();

                /* Expire outdated class/list items */
                Class_Expire();

                /* Look for non-empty read buffers ... */
                for (i = 0; i < Pool_Size; i++) {
                        if ((My_Connections[i].sock > NONE)
                            && (array_bytes(&My_Connections[i].rbuf) > 0)) {
                                /* ... and try to handle the received data */
                                Handle_Buffer(i);
                        }
                }

                /* Look for non-empty write buffers ... */
                for (i = 0; i < Pool_Size; i++) {
                        if (My_Connections[i].sock <= NONE)
                                continue;

                        wdatalen = array_bytes(&My_Connections[i].wbuf);
#ifdef ZLIB
                        if (wdatalen > 0 ||
                            array_bytes(&My_Connections[i].zip.wbuf) > 0)
#else
                        if (wdatalen > 0)
#endif
                        {
#ifdef SSL_SUPPORT
                                if (SSL_WantRead(&My_Connections[i]))
                                        continue;
#endif
                                io_event_add(My_Connections[i].sock,
                                             IO_WANTWRITE);
                        }
                }

                /* Check from which sockets we possibly could read ... */
                for (i = 0; i < Pool_Size; i++) {
                        if (My_Connections[i].sock <= NONE)
                                continue;
#ifdef SSL_SUPPORT
                        if (SSL_WantWrite(&My_Connections[i]))
                                /* TLS/SSL layer needs to write data; deal
                                 * with this first! */
                                continue;
#endif
                        if (Proc_InProgress(&My_Connections[i].proc_stat)) {
                                /* Wait for completion of forked subprocess
                                 * and ignore the socket in the meantime ... */
                                io_event_del(My_Connections[i].sock,
                                             IO_WANTREAD);
                                continue;
                        }

                        if (Conn_OPTION_ISSET(&My_Connections[i], CONN_ISCONNECTING))
                                /* Wait for completion of connect() ... */
                                continue;

                        if (My_Connections[i].delaytime > t) {
                                /* There is a "penalty time" set: ignore socket! */
                                io_event_del(My_Connections[i].sock,
                                             IO_WANTREAD);
                                continue;
                        }

                        if (array_bytes(&My_Connections[i].rbuf) >= COMMAND_LEN) {
                                /* There is still more data in the read buffer
                                 * than a single valid command can get long:
                                 * so either there is a complete command, or
                                 * invalid data. Therefore don't try to read in
                                 * even more data from the network but wait for
                                 * this command(s) to be handled first! */
                                io_event_del(My_Connections[i].sock,
                                             IO_WANTREAD);
                                command_available = true;
                                continue;
                        }

                        io_event_add(My_Connections[i].sock, IO_WANTREAD);
                }

                /* Don't wait for data when there is still at least one command
                 * available in a read buffer which can be handled immediately;
                 * set the timeout for reading from the network to 1 second
                 * otherwise, which is the granularity with witch we handle
                 * "penalty times" for example.
                 * Note: tv_sec/usec are undefined(!) after io_dispatch()
                 * returns, so we have to set it before each call to it! */
                tv.tv_usec = 0;
                tv.tv_sec = command_available ? 0 : 1;

                /* Wait for activity ... */
                i = io_dispatch(&tv);
                if (i == -1 && errno != EINTR) {
                        Log(LOG_EMERG, "Conn_Handler(): io_dispatch(): %s!",
                            strerror(errno));
                        Log(LOG_ALERT, "%s exiting due to fatal errors!",
                            PACKAGE_NAME);
                        exit(1);
                }

                t = time(NULL);
                if (Conf_IdleTimeout > 0 && NumConnectionsAccepted > 0
                    && idle_t > 0 && t - idle_t >= Conf_IdleTimeout) {
                        /* Should ngIRCd timeout when idle? */
                        LogDebug("Server idle timeout reached: %d second%s. Initiating shutdown ...",
                                 Conf_IdleTimeout,
                                 Conf_IdleTimeout == 1 ? "" : "s");
                        NGIRCd_SignalQuit = true;
                } else if (Signal_NotifySvcMgr_Possible() && t - notify_t > 3) {
                        /* Send the current status to the service manager. */
                        snprintf(status, sizeof(status),
                                 "WATCHDOG=1\nSTATUS=%ld connection%s established (%ld user%s, %ld server%s), %ld maximum. %ld accepted in total.\n",
                                 NumConnections, NumConnections == 1 ? "" : "s",
                                 Client_MyUserCount(), Client_MyUserCount() == 1 ? "" : "s",
                                 Client_MyServerCount(), Client_MyServerCount() == 1 ? "" : "s",
                                 NumConnectionsMax, NumConnectionsAccepted);
                        Signal_NotifySvcMgr(status);
                        notify_t = t;
                }
        }

        if (NGIRCd_SignalQuit) {
                Log(LOG_NOTICE | LOG_snotice, "Server going down NOW!");
                Signal_NotifySvcMgr("STOPPING=1\n");
        } else if (NGIRCd_SignalRestart) {
                Log(LOG_NOTICE | LOG_snotice, "Server restarting NOW!");
                Signal_NotifySvcMgr("RELOADING=1\n");
        }
} /* Conn_Handler */

/**
 * Write a text string into the socket of a connection.
 *
 * This function automatically appends CR+LF to the string and validates that
 * the result is a valid IRC message (oversized messages are shortened, for
 * example). Then it calls the Conn_Write() function to do the actual sending.
 *
 * @param Idx           Index of the connection.
 * @param Format        Format string, see printf().
 * @returns             true on success, false otherwise.
 */
#ifdef PROTOTYPES
GLOBAL bool
Conn_WriteStr(CONN_ID Idx, const char *Format, ...)
#else
GLOBAL bool
Conn_WriteStr(Idx, Format, va_alist)
CONN_ID Idx;
const char *Format;
va_dcl
#endif
{
        char buffer[COMMAND_LEN];
#ifdef ICONV
        char *ptr, *message;
#endif
        size_t len;
        bool ok;
        va_list ap;
        int r;

        assert( Idx > NONE );
        assert( Format != NULL );

#ifdef PROTOTYPES
        va_start( ap, Format );
#else
        va_start( ap );
#endif
        r = vsnprintf(buffer, COMMAND_LEN - 2, Format, ap);
        if (r >= COMMAND_LEN - 2 || r == -1) {
                /*
                 * The string that should be written to the socket is longer
                 * than the allowed size of COMMAND_LEN bytes (including both
                 * the CR and LF characters). This can be caused by the
                 * IRC_WriteXXX() functions when the prefix of this server had
                 * to be added to an already "quite long" command line which
                 * has been received from a regular IRC client, for example.
                 *
                 * We are not allowed to send such "oversized" messages to
                 * other servers and clients, see RFC 2812 2.3 and 2813 3.3
                 * ("these messages SHALL NOT exceed 512 characters in length,
                 * counting all characters including the trailing CR-LF").
                 *
                 * So we have a big problem here: we should send more bytes
                 * to the network than we are allowed to and we don't know
                 * the originator (any more). The "old" behavior of blaming
                 * the receiver ("next hop") is a bad idea (it could be just
                 * an other server only routing the message!), so the only
                 * option left is to shorten the string and to hope that the
                 * result is still somewhat useful ...
                 *
                 * Note:
                 * C99 states that vsnprintf() "returns the number of characters
                 * that would have been printed if the n were unlimited"; but
                 * according to the Linux manual page "glibc until 2.0.6 would
                 * return -1 when the output was truncated" -- so we have to
                 * handle both cases ...
                 *                                                   -alex-
                 */

                strcpy (buffer + sizeof(buffer) - strlen(CUT_TXTSUFFIX) - 2 - 1,
                        CUT_TXTSUFFIX);
        }

#ifdef ICONV
        ptr = strchr(buffer + 1, ':');
        if (ptr) {
                ptr++;
                message = Conn_EncodingTo(Idx, ptr);
                if (message != ptr)
                        strlcpy(ptr, message, sizeof(buffer) - (ptr - buffer));
        }
#endif

#ifdef SNIFFER
        if (NGIRCd_Sniffer)
                LogDebug("-> connection %d: '%s'.", Idx, buffer);
#endif

        len = strlcat( buffer, "\r\n", sizeof( buffer ));
        ok = Conn_Write(Idx, buffer, len);
        My_Connections[Idx].msg_out++;

        va_end( ap );
        return ok;
} /* Conn_WriteStr */

GLOBAL char*
Conn_Password( CONN_ID Idx )
{
        assert( Idx > NONE );
        if (My_Connections[Idx].pwd == NULL)
                return (char*)"\0";
        else
                return My_Connections[Idx].pwd;
} /* Conn_Password */

GLOBAL void
Conn_SetPassword( CONN_ID Idx, const char *Pwd )
{
        assert( Idx > NONE );

        if (My_Connections[Idx].pwd)
                free(My_Connections[Idx].pwd);

        My_Connections[Idx].pwd = strdup(Pwd);
        if (My_Connections[Idx].pwd == NULL) {
                Log(LOG_EMERG, "Can't allocate memory! [Conn_SetPassword]");
                exit(1);
        }
} /* Conn_SetPassword */

/**
 * Append Data to the outbound write buffer of a connection.
 *
 * @param Idx   Index of the connection.
 * @param Data  pointer to the data.
 * @param Len   length of Data.
 * @returns     true on success, false otherwise.
 */
static bool
Conn_Write( CONN_ID Idx, char *Data, size_t Len )
{
        CLIENT *c;
        size_t writebuf_limit = WRITEBUFFER_MAX_LEN;
        assert( Idx > NONE );
        assert( Data != NULL );
        assert( Len > 0 );

        /* Is the socket still open? A previous call to Conn_Write()
         * may have closed the connection due to a fatal error.
         * In this case it is sufficient to return an error, as well. */
        if (My_Connections[Idx].sock <= NONE) {
                LogDebug("Skipped write on closed socket (connection %d).", Idx);
                return false;
        }

        /* Make sure that there still exists a CLIENT structure associated
         * with this connection and check if this is a server or not: */
        c = Conn_GetClient(Idx);
        if (c) {
                /* Servers do get special write buffer limits, so they can
                 * generate all the messages that are required while peering. */
                if (Client_Type(c) == CLIENT_SERVER)
                        writebuf_limit = WRITEBUFFER_SLINK_LEN;
        } else
                LogDebug("Write on socket without client (connection %d)!?", Idx);

#ifdef ZLIB
        if ( Conn_OPTION_ISSET( &My_Connections[Idx], CONN_ZIP )) {
                /* Compressed link:
                 * Zip_Buffer() does all the dirty work for us: it flushes
                 * the (pre-)compression buffers if required and handles
                 * all error conditions. */
                if (!Zip_Buffer(Idx, Data, Len))
                        return false;
        }
        else
#endif
        {
                /* Uncompressed link:
                 * Check if outbound buffer has enough space for the data. */
                if (array_bytes(&My_Connections[Idx].wbuf) + Len >=
                    WRITEBUFFER_FLUSH_LEN) {
                        /* Buffer is full, flush it. Handle_Write deals with
                         * low-level errors, if any. */
                        if (!Handle_Write(Idx))
                                return false;
                }

                /* When the write buffer is still too big after flushing it,
                 * the connection will be killed. */
                if (array_bytes(&My_Connections[Idx].wbuf) + Len >=
                    writebuf_limit) {
                        Log(LOG_NOTICE,
                            "Write buffer space exhausted (connection %d, limit is %lu bytes, %lu bytes new, %lu bytes pending)",
                            Idx, writebuf_limit, Len,
                            (unsigned long)array_bytes(&My_Connections[Idx].wbuf));
                        Conn_Close(Idx, "Write buffer space exhausted", NULL, false);
                        return false;
                }

                /* Copy data to write buffer */
                if (!array_catb(&My_Connections[Idx].wbuf, Data, Len))
                        return false;

                My_Connections[Idx].bytes_out += Len;
        }

        /* Adjust global write counter */
        WCounter += Len;

        return true;
} /* Conn_Write */

/**
 * Shut down a connection.
 *
 * @param Idx           Connection index.
 * @param LogMsg        Message to write to the log or NULL. If no LogMsg
 *                      is given, the FwdMsg is logged.
 * @param FwdMsg        Message to forward to remote servers.
 * @param InformClient  If true, inform the client on the connection which is
 *                      to be shut down of the reason (FwdMsg) and send
 *                      connection statistics before disconnecting it.
 */
GLOBAL void
Conn_Close(CONN_ID Idx, const char *LogMsg, const char *FwdMsg, bool InformClient)
{
        /* Close connection. Open pipes of asynchronous resolver
         * sub-processes are closed down. */

        CLIENT *c;
        double in_k, out_k;
        UINT16 port;
#ifdef ZLIB
        double in_z_k, out_z_k;
        int in_p, out_p;
#endif

        assert( Idx > NONE );

        /* Is this link already shutting down? */
        if( Conn_OPTION_ISSET( &My_Connections[Idx], CONN_ISCLOSING )) {
                /* Conn_Close() has been called recursively for this link;
                 * probable reason: Handle_Write() failed -- see below. */
                LogDebug("Recursive request to close connection %d!", Idx );
                return;
        }

        assert( My_Connections[Idx].sock > NONE );

        /* Mark link as "closing" */
        Conn_OPTION_ADD( &My_Connections[Idx], CONN_ISCLOSING );

        port = ng_ipaddr_getport(&My_Connections[Idx].addr);
        Log(LOG_INFO, "Shutting down connection %d (%s) with \"%s:%d\" ...", Idx,
            LogMsg ? LogMsg : FwdMsg, My_Connections[Idx].host, port);

        /* Search client, if any */
        c = Conn_GetClient( Idx );

        /* Should the client be informed? */
        if (InformClient) {
#ifndef STRICT_RFC
                /* Send statistics to client if registered as user: */
                if ((c != NULL) && (Client_Type(c) == CLIENT_USER)) {
                        Conn_WriteStr( Idx,
                         ":%s NOTICE %s :%sConnection statistics: client %.1f kb, server %.1f kb.",
                         Client_ID(Client_ThisServer()), Client_ID(c),
                         NOTICE_TXTPREFIX,
                         (double)My_Connections[Idx].bytes_in / 1024,
                         (double)My_Connections[Idx].bytes_out / 1024);
                }
#endif
                /* Send ERROR to client (see RFC 2812, section 3.1.7) */
                if (c)
                        Conn_WriteStr(Idx, "ERROR :Closing connection: %s[%s@%s] (%s)",
                                      Client_ID(c), Client_User(c), Client_Hostname(c),
                                      FwdMsg ? FwdMsg : "\"\"");
                else
                        Conn_WriteStr(Idx, "ERROR :Closing connection");
        }

        /* Try to write out the write buffer. Note: Handle_Write() eventually
         * removes the CLIENT structure associated with this connection if an
         * error occurs! So we have to re-check if there is still an valid
         * CLIENT structure after calling Handle_Write() ...*/
        (void)Handle_Write( Idx );

        /* Search client, if any (re-check!) */
        c = Conn_GetClient( Idx );
#ifdef SSL_SUPPORT
        if ( Conn_OPTION_ISSET( &My_Connections[Idx], CONN_SSL )) {
                LogDebug("SSL connection %d shutting down ...", Idx);
                ConnSSL_Free(&My_Connections[Idx]);
        }
#endif
        /* Shut down socket */
        if (! io_close(My_Connections[Idx].sock)) {
                /* Oops, we can't close the socket!? This is ... ugly! */
                Log(LOG_CRIT,
                    "Error closing connection %d (socket %d) with %s:%d - %s! (ignored)",
                    Idx, My_Connections[Idx].sock, My_Connections[Idx].host,
                    port, strerror(errno));
        }

        /* Mark socket as invalid: */
        My_Connections[Idx].sock = NONE;

        /* If there is still a client, unregister it now */
        if (c)
                Client_Destroy(c, LogMsg, FwdMsg, true);

        /* Calculate statistics and log information */
        in_k = (double)My_Connections[Idx].bytes_in / 1024;
        out_k = (double)My_Connections[Idx].bytes_out / 1024;
#ifdef ZLIB
        if (Conn_OPTION_ISSET( &My_Connections[Idx], CONN_ZIP)) {
                in_z_k = (double)My_Connections[Idx].zip.bytes_in / 1024;
                out_z_k = (double)My_Connections[Idx].zip.bytes_out / 1024;
                /* Make sure that no division by zero can occur during
                 * the calculation of in_p and out_p: in_z_k and out_z_k
                 * are non-zero, that's guaranteed by the protocol until
                 * compression can be enabled. */
                if (in_z_k <= 0)
                        in_z_k = in_k;
                if (out_z_k <= 0)
                        out_z_k = out_k;
                in_p = (int)(( in_k * 100 ) / in_z_k );
                out_p = (int)(( out_k * 100 ) / out_z_k );
                Log(LOG_INFO,
                    "Connection %d with \"%s:%d\" closed (in: %.1fk/%.1fk/%d%%, out: %.1fk/%.1fk/%d%%).",
                    Idx, My_Connections[Idx].host, port,
                    in_k, in_z_k, in_p, out_k, out_z_k, out_p);
        }
        else
#endif
        {
                Log(LOG_INFO,
                    "Connection %d with \"%s:%d\" closed (in: %.1fk, out: %.1fk).",
                    Idx, My_Connections[Idx].host, port,
                    in_k, out_k);
        }

        /* Servers: Modify time of next connect attempt? */
        Conf_UnsetServer( Idx );

#ifdef ZLIB
        /* Clean up zlib, if link was compressed */
        if ( Conn_OPTION_ISSET( &My_Connections[Idx], CONN_ZIP )) {
                inflateEnd( &My_Connections[Idx].zip.in );
                deflateEnd( &My_Connections[Idx].zip.out );
                array_free(&My_Connections[Idx].zip.rbuf);
                array_free(&My_Connections[Idx].zip.wbuf);
        }
#endif

        array_free(&My_Connections[Idx].rbuf);
        array_free(&My_Connections[Idx].wbuf);
        if (My_Connections[Idx].pwd != NULL)
                free(My_Connections[Idx].pwd);

        /* Clean up connection structure (=free it) */
        Init_Conn_Struct( Idx );

        assert(NumConnections > 0);
        if (NumConnections)
                NumConnections--;
        LogDebug("Shutdown of connection %d completed, %ld connection%s left.",
                 Idx, NumConnections, NumConnections != 1 ? "s" : "");

        idle_t = NumConnections > 0 ? 0 : time(NULL);
} /* Conn_Close */

/**
 * Get current number of connections.
 *
 * @returns     Number of current connections.
 */
GLOBAL long
Conn_Count(void)
{
        return NumConnections;
} /* Conn_Count */

/**
 * Get number of maximum simultaneous connections.
 *
 * @returns     Number of maximum simultaneous connections.
 */
GLOBAL long
Conn_CountMax(void)
{
        return NumConnectionsMax;
} /* Conn_CountMax */

/**
 * Get number of connections accepted since the daemon started.
 *
 * @returns     Number of connections accepted.
 */
GLOBAL long
Conn_CountAccepted(void)
{
        return NumConnectionsAccepted;
} /* Conn_CountAccepted */

/**
 * Synchronize established connections and configured server structures
 * after a configuration update and store the correct connection IDs, if any.
 */
GLOBAL void
Conn_SyncServerStruct(void)
{
        CLIENT *client;
        CONN_ID i;
        int c;

        for (i = 0; i < Pool_Size; i++) {
                if (My_Connections[i].sock == NONE)
                        continue;

                /* Server link? */
                client = Conn_GetClient(i);
                if (!client || Client_Type(client) != CLIENT_SERVER)
                        continue;

                for (c = 0; c < MAX_SERVERS; c++) {
                        /* Configured server? */
                        if (!Conf_Server[c].host[0])
                                continue;

                        if (strcasecmp(Conf_Server[c].name, Client_ID(client)) == 0)
                                Conf_Server[c].conn_id = i;
                }
        }
} /* SyncServerStruct */

/**
 * Get IP address string of a connection.
 *
 * @param Idx Connection index.
 * @return Pointer to a global buffer containing the IP address as string.
 */
GLOBAL const char *
Conn_GetIPAInfo(CONN_ID Idx)
{
        assert(Idx > NONE);
        return ng_ipaddr_tostr(&My_Connections[Idx].addr);
}

/**
 * Send out data of write buffer; connect new sockets.
 *
 * @param Idx   Connection index.
 * @returns     true on success, false otherwise.
 */
static bool
Handle_Write( CONN_ID Idx )
{
        ssize_t len;
        size_t wdatalen;

        assert( Idx > NONE );
        if ( My_Connections[Idx].sock < 0 ) {
                LogDebug("Handle_Write() on closed socket, connection %d", Idx);
                return false;
        }
        assert( My_Connections[Idx].sock > NONE );

        wdatalen = array_bytes(&My_Connections[Idx].wbuf );

#ifdef ZLIB
        if (wdatalen == 0) {
                /* Write buffer is empty, so we try to flush the compression
                 * buffer and get some data to work with from there :-) */
                if (!Zip_Flush(Idx))
                        return false;

                /* Now the write buffer most probably has changed: */
                wdatalen = array_bytes(&My_Connections[Idx].wbuf);
        }
#endif

        if (wdatalen == 0) {
                /* Still no data, fine. */
                io_event_del(My_Connections[Idx].sock, IO_WANTWRITE );
                return true;
        }

#if DEBUG_BUFFER
        LogDebug
            ("Handle_Write() called for connection %d, %ld bytes pending ...",
             Idx, wdatalen);
#endif

#ifdef SSL_SUPPORT
        if ( Conn_OPTION_ISSET( &My_Connections[Idx], CONN_SSL )) {
                len = ConnSSL_Write(&My_Connections[Idx],
                                    array_start(&My_Connections[Idx].wbuf),
                                    wdatalen);
        } else
#endif
        {
                len = write(My_Connections[Idx].sock,
                            array_start(&My_Connections[Idx].wbuf), wdatalen );
        }
        if( len < 0 ) {
                if (errno == EAGAIN || errno == EINTR)
                        return true;

                if (!Conn_OPTION_ISSET(&My_Connections[Idx], CONN_ISCLOSING)) {
                        Log(LOG_ERR,
                            "Write error on connection %d (socket %d): %s!",
                            Idx, My_Connections[Idx].sock, strerror(errno));
                        Conn_Close(Idx, "Write error", NULL, false);
                } else
                        LogDebug("Recursive write error on connection %d (socket %d): %s!",
                                 Idx, My_Connections[Idx].sock, strerror(errno));

                return false;
        }

        /* move any data not yet written to beginning */
        array_moveleft(&My_Connections[Idx].wbuf, 1, (size_t)len);

        return true;
} /* Handle_Write */

/**
 * Count established connections to a specific IP address.
 *
 * @returns     Number of established connections.
 */
static int
Count_Connections(ng_ipaddr_t *a)
{
        int i, cnt;

        cnt = 0;
        for (i = 0; i < Pool_Size; i++) {
                if (My_Connections[i].sock <= NONE)
                        continue;
                if (ng_ipaddr_ipequal(&My_Connections[i].addr, a))
                        cnt++;
        }
        return cnt;
} /* Count_Connections */

/**
 * Initialize new client connection on a listening socket.
 *
 * @param Sock  Listening socket descriptor.
 * @param IsSSL true if this socket expects SSL-encrypted data.
 * @returns     Accepted socket descriptor or -1 on error.
 */
static int
New_Connection(int Sock, UNUSED bool IsSSL)
{
#ifdef TCPWRAP
        struct request_info req;
#endif
        ng_ipaddr_t new_addr;
        char ip_str[NG_INET_ADDRSTRLEN];
        int new_sock, new_sock_len;
        CLIENT *c;
        long cnt;

        assert(Sock > NONE);

        LogDebug("Accepting new connection on socket %d ...", Sock);

        new_sock_len = (int)sizeof(new_addr);
        new_sock = accept(Sock, (struct sockaddr *)&new_addr,
                          (socklen_t *)&new_sock_len);
        if (new_sock < 0) {
                Log(LOG_CRIT, "Can't accept connection on socket %d: %s!",
                    Sock, strerror(errno));
                return -1;
        }
        NumConnectionsAccepted++;

        if (!ng_ipaddr_tostr_r(&new_addr, ip_str)) {
                Log(LOG_CRIT, "Can't convert peer IP address of socket %d!", new_sock);
                Simple_Message(new_sock, "ERROR :Internal Server Error");
                close(new_sock);
                return -1;
        }

#ifdef TCPWRAP
        /* Validate socket using TCP Wrappers */
        request_init(&req, RQ_DAEMON, PACKAGE_NAME, RQ_FILE, new_sock,
                     RQ_CLIENT_SIN, &new_addr, NULL);
        fromhost(&req);
        if (!hosts_access(&req)) {
                Log(deny_severity,
                    "Refused connection from %s on socket %d (by TCP Wrappers)!",
                    ip_str, Sock);
                Simple_Message(new_sock, "ERROR :Connection refused");
                close(new_sock);
                return -1;
        }
#endif

        if (!Init_Socket(new_sock))
                return -1;

        /* Check global connection limit */
        if ((Conf_MaxConnections > 0) &&
            (NumConnections >= (size_t) Conf_MaxConnections)) {
                Log(LOG_ALERT, "Can't accept new connection on socket %d: Limit (%d) reached!",
                    Sock, Conf_MaxConnections);
                Simple_Message(new_sock, "ERROR :Connection limit reached");
                close(new_sock);
                return -1;
        }

        /* Check IP-based connection limit */
        cnt = Count_Connections(&new_addr);
        if ((Conf_MaxConnectionsIP > 0) && (cnt >= Conf_MaxConnectionsIP)) {
                /* Access denied, too many connections from this IP address! */
                Log(LOG_ERR,
                    "Refused connection from %s on socket %d: too may connections (%ld) from this IP address!",
                    ip_str, Sock, cnt);
                Simple_Message(new_sock,
                               "ERROR :Connection refused, too many connections from your IP address");
                close(new_sock);
                return -1;
        }

        if (Socket2Index(new_sock) <= NONE) {
                Simple_Message(new_sock, "ERROR: Internal error");
                close(new_sock);
                return -1;
        }

        /* register callback */
        if (!io_event_create(new_sock, IO_WANTREAD, cb_clientserver)) {
                Log(LOG_ALERT,
                    "Can't accept connection: io_event_create failed!");
                Simple_Message(new_sock, "ERROR :Internal error");
                close(new_sock);
                return -1;
        }

        c = Client_NewLocal(new_sock, NULL, CLIENT_UNKNOWN, false);
        if (!c) {
                Log(LOG_ALERT,
                    "Can't accept connection: can't create client structure!");
                Simple_Message(new_sock, "ERROR :Internal error");
                io_close(new_sock);
                return -1;
        }

        Init_Conn_Struct(new_sock);
        My_Connections[new_sock].sock = new_sock;
        My_Connections[new_sock].addr = new_addr;
        My_Connections[new_sock].client = c;

        /* Set initial hostname to IP address. This becomes overwritten when
         * the DNS lookup is enabled and succeeds, but is used otherwise. */
        if (ng_ipaddr_af(&new_addr) != AF_INET)
                snprintf(My_Connections[new_sock].host,
                         sizeof(My_Connections[new_sock].host), "[%s]", ip_str);
        else
                strlcpy(My_Connections[new_sock].host, ip_str,
                        sizeof(My_Connections[new_sock].host));

        Client_SetHostname(c, My_Connections[new_sock].host);

        Log(LOG_INFO, "Accepted connection %d from \"%s:%d\" on socket %d.",
            new_sock, My_Connections[new_sock].host,
            ng_ipaddr_getport(&new_addr), Sock);
        Account_Connection();

#ifdef SSL_SUPPORT
        /* Delay connection initialization until SSL handshake is finished */
        if (!IsSSL)
#endif
                Conn_StartLogin(new_sock);

        return new_sock;
} /* New_Connection */

/**
 * Finish connection initialization, start resolver subprocess.
 *
 * @param Idx Connection index.
 */
GLOBAL void
Conn_StartLogin(CONN_ID Idx)
{
        int ident_sock = -1;

        assert(Idx >= 0);

#ifdef IDENTAUTH
        /* Should we make an IDENT request? */
        if (Conf_Ident)
                ident_sock = My_Connections[Idx].sock;
#endif

        if (Conf_NoticeBeforeRegistration) {
                /* Send "NOTICE *" messages to the client */
#ifdef IDENTAUTH
                if (Conf_Ident) {
                        if (Conf_DNS)
                                (void)Conn_WriteStr(Idx,
                                        "NOTICE * :*** Looking up your hostname and checking ident");
                        else
                                (void)Conn_WriteStr(Idx,
                                        "NOTICE * :*** Checking ident");
                } else
#endif
                if(Conf_DNS)
                        (void)Conn_WriteStr(Idx,
                                "NOTICE * :*** Looking up your hostname");
                else
                        (void)Conn_WriteStr(Idx,
                                "NOTICE * :*** Processing your connection");
                /* Send buffered data to the client, but break on errors
                 * because Handle_Write() would have closed the connection
                 * again in this case! */
                if (!Handle_Write(Idx))
                        return;
        }

        Resolve_Addr_Ident(&My_Connections[Idx].proc_stat,
                           &My_Connections[Idx].addr,
                           ident_sock, cb_Read_Resolver_Result);
}

/**
 * Update global connection counters.
 */
static void
Account_Connection(void)
{
        NumConnections++;
        idle_t = 0;
        if (NumConnections > NumConnectionsMax)
                NumConnectionsMax = NumConnections;
        LogDebug("Total number of connections now %lu (max %lu).",
                 NumConnections, NumConnectionsMax);
} /* Account_Connection */

/**
 * Translate socket handle into connection index (for historical reasons, it is
 * a 1:1 mapping today) and enlarge the "connection pool" accordingly.
 *
 * @param Sock  Socket handle.
 * @returns     Connection index or NONE when the pool is too small.
 */
static CONN_ID
Socket2Index( int Sock )
{
        assert(Sock > 0);
        assert(Pool_Size >= 0);

        if (Sock < Pool_Size)
                return Sock;

        /* Try to allocate more memory ... */
        if (!array_alloc(&My_ConnArray, sizeof(CONNECTION), (size_t)Sock)) {
                Log(LOG_EMERG,
                    "Can't allocate memory to enlarge connection pool!");
                return NONE;
        }
        LogDebug("Enlarged connection pool for %ld sockets (%ld items, %ld bytes)",
                 Sock, array_length(&My_ConnArray, sizeof(CONNECTION)),
                 array_bytes(&My_ConnArray));

        /* Adjust pointer to new block, update size and initialize new items. */
        My_Connections = array_start(&My_ConnArray);
        while (Pool_Size <= Sock)
                Init_Conn_Struct(Pool_Size++);

        return Sock;
}

/**
 * Read data from the network to the read buffer. If an error occurs,
 * the socket of this connection will be shut down.
 *
 * @param Idx   Connection index.
 */
static void
Read_Request(CONN_ID Idx)
{
        ssize_t len;
        static const unsigned int maxbps = COMMAND_LEN / 2;
        char readbuf[READBUFFER_LEN];
        time_t t;
        CLIENT *c;

        assert(Idx > NONE);
        assert(My_Connections[Idx].sock > NONE);

        /* Check if the read buffer is "full". Basically this shouldn't happen
         * here, because as long as there possibly are commands in the read
         * buffer (buffer usage > COMMAND_LEN), the socket shouldn't be
         * scheduled for reading in Conn_Handler() at all ... */
#ifdef ZLIB
        if ((array_bytes(&My_Connections[Idx].rbuf) >= READBUFFER_LEN) ||
                (array_bytes(&My_Connections[Idx].zip.rbuf) >= READBUFFER_LEN))
#else
        if (array_bytes(&My_Connections[Idx].rbuf) >= READBUFFER_LEN)
#endif
        {
                Log(LOG_ERR,
                    "Receive buffer space exhausted (connection %d): %d/%d bytes",
                    Idx, array_bytes(&My_Connections[Idx].rbuf), READBUFFER_LEN);
                Conn_Close(Idx, "Receive buffer space exhausted", NULL, false);
                return;
        }

        /* Now read new data from the network, up to READBUFFER_LEN bytes ... */
#ifdef SSL_SUPPORT
        if (Conn_OPTION_ISSET(&My_Connections[Idx], CONN_SSL))
                len = ConnSSL_Read(&My_Connections[Idx], readbuf, sizeof(readbuf));
        else
#endif
                len = read(My_Connections[Idx].sock, readbuf, sizeof(readbuf));

        if (len == 0) {
                LogDebug("Client \"%s:%u\" is closing connection %d ...",
                         My_Connections[Idx].host,
                         ng_ipaddr_getport(&My_Connections[Idx].addr), Idx);
                Conn_Close(Idx, NULL, "Client closed connection", false);
                return;
        }

        if (len < 0) {
                if (errno == EAGAIN)
                        return;

                Log(LOG_ERR, "Read error on connection %d (socket %d): %s!",
                    Idx, My_Connections[Idx].sock, strerror(errno));
                Conn_Close(Idx, "Read error", "Client closed connection",
                           false);
                return;
        }

        /* Now append the newly received data to the connection buffer.
         * NOTE: This can lead to connection read buffers being bigger(!) than
         * READBUFFER_LEN bytes, as we add up to READBUFFER_LEN new bytes to a
         * buffer possibly being "almost" READBUFFER_LEN bytes already! */
#ifdef ZLIB
        if (Conn_OPTION_ISSET(&My_Connections[Idx], CONN_ZIP)) {
                if (!array_catb(&My_Connections[Idx].zip.rbuf, readbuf,
                                (size_t) len)) {
                        Log(LOG_ERR,
                            "Could not append received data to zip input buffer (connection %d): %d bytes!",
                            Idx, len);
                        Conn_Close(Idx, "Receive buffer space exhausted", NULL,
                                   false);
                        return;
                }
        } else
#endif
        {
                if (!array_catb( &My_Connections[Idx].rbuf, readbuf, len)) {
                        Log(LOG_ERR,
                            "Could not append received data to input buffer (connection %d): %d bytes!",
                            Idx, len);
                        Conn_Close(Idx, "Receive buffer space exhausted", NULL,
                                   false );
                }
        }

        /* Update connection statistics */
        My_Connections[Idx].bytes_in += len;

        /* Handle read buffer */
        My_Connections[Idx].bps += Handle_Buffer(Idx);

        /* Make sure that there is still a valid client registered */
        c = Conn_GetClient(Idx);
        if (!c)
                return;

        /* Update timestamp of last data received if this connection is
         * registered as a user, server or service connection. Don't update
         * otherwise, so users have at least Conf_PongTimeout seconds time to
         * register with the IRC server -- see Check_Connections().
         * Update "lastping", too, if time shifted backwards ... */
        if (Client_Type(c) == CLIENT_USER
            || Client_Type(c) == CLIENT_SERVER
            || Client_Type(c) == CLIENT_SERVICE) {
                t = time(NULL);
                if (My_Connections[Idx].lastdata != t)
                        My_Connections[Idx].bps = 0;

                My_Connections[Idx].lastdata = t;
                if (My_Connections[Idx].lastping > t)
                        My_Connections[Idx].lastping = t;
        }

        /* Look at the data in the (read-) buffer of this connection */
        if (My_Connections[Idx].bps >= maxbps)
                Throttle_Connection(Idx, c, THROTTLE_BPS, maxbps);
} /* Read_Request */

/**
 * Handle all data in the connection read-buffer.
 *
 * Data is processed until no complete command is left in the read buffer,
 * or MAX_COMMANDS[_SERVER|_SERVICE] commands were processed.
 * When a fatal error occurs, the connection is shut down.
 *
 * @param Idx   Index of the connection.
 * @returns     Number of bytes processed.
 */
static unsigned int
Handle_Buffer(CONN_ID Idx)
{
#ifndef STRICT_RFC
        char *ptr1, *ptr2, *first_eol;
#endif
        char *ptr;
        size_t len, delta;
        time_t starttime;
#ifdef ZLIB
        bool old_z;
#endif
        unsigned int i, maxcmd = MAX_COMMANDS, len_processed = 0;
        CLIENT *c;

        c = Conn_GetClient(Idx);
        starttime = time(NULL);

        assert(c != NULL);

        /* Servers get special command limits that depend on the user count */
        switch (Client_Type(c)) {
            case CLIENT_SERVER:
                maxcmd = (int)(Client_UserCount() / 5)
                       + MAX_COMMANDS_SERVER_MIN;
                /* Allow servers to handle even more commands while peering
                 * to speed up server login and network synchronization. */
                if (Conn_LastPing(Idx) == 0)
                        maxcmd *= 5;
                break;
            case CLIENT_SERVICE:
                maxcmd = MAX_COMMANDS_SERVICE;
                break;
            case CLIENT_USER:
                if (Client_HasMode(c, 'F'))
                        maxcmd = MAX_COMMANDS_SERVICE;
                break;
        }

        for (i=0; i < maxcmd; i++) {
                /* Check penalty */
                if (My_Connections[Idx].delaytime > starttime)
                        return 0;
#ifdef ZLIB
                /* Unpack compressed data, if compression is in use */
                if (Conn_OPTION_ISSET(&My_Connections[Idx], CONN_ZIP)) {
                        /* When unzipping fails, Unzip_Buffer() shuts
                         * down the connection itself */
                        if (!Unzip_Buffer(Idx))
                                return 0;
                }
#endif

                if (0 == array_bytes(&My_Connections[Idx].rbuf))
                        break;

                /* Make sure that the buffer is NULL terminated */
                if (!array_cat0_temporary(&My_Connections[Idx].rbuf)) {
                        Conn_Close(Idx, NULL,
                                   "Can't allocate memory [Handle_Buffer]",
                                   true);
                        return 0;
                }

                /* RFC 2812, section "2.3 Messages", 5th paragraph:
                 * "IRC messages are always lines of characters terminated
                 * with a CR-LF (Carriage Return - Line Feed) pair [...]". */
                delta = 2;
                ptr = strstr(array_start(&My_Connections[Idx].rbuf), "\r\n");

#ifndef STRICT_RFC
                /* Check for non-RFC-compliant request (only CR or LF)?
                 * Unfortunately, there are quite a few clients out there
                 * that do this -- e. g. mIRC, BitchX, and Trillian :-( */
                ptr1 = strchr(array_start(&My_Connections[Idx].rbuf), '\r');
                ptr2 = strchr(array_start(&My_Connections[Idx].rbuf), '\n');
                if (ptr) {
                        /* Check if there is a single CR or LF _before_ the
                         * correct CR+LF line terminator:  */
                        first_eol = ptr1 < ptr2 ? ptr1 : ptr2;
                        if (first_eol < ptr) {
                                /* Single CR or LF before CR+LF found */
                                ptr = first_eol;
                                delta = 1;
                        }
                } else if (ptr1 || ptr2) {
                        /* No CR+LF terminated command found, but single
                         * CR or LF found ... */
                        if (ptr1 && ptr2)
                                ptr = ptr1 < ptr2 ? ptr1 : ptr2;
                        else
                                ptr = ptr1 ? ptr1 : ptr2;
                        delta = 1;
                }
#endif

                if (!ptr)
                        break;

                /* Complete (=line terminated) request found, handle it! */
                *ptr = '\0';

                len = ptr - (char *)array_start(&My_Connections[Idx].rbuf) + delta;

                if (len > (COMMAND_LEN - 1)) {
                        /* Request must not exceed 512 chars (incl. CR+LF!),
                         * see RFC 2812. Disconnect Client if this happens. */
                        Log(LOG_ERR,
                            "Request too long (connection %d): %d bytes (max. %d expected)!",
                            Idx, array_bytes(&My_Connections[Idx].rbuf),
                            COMMAND_LEN - 1);
                        Conn_Close(Idx, NULL, "Request too long", true);
                        return 0;
                }

                len_processed += (unsigned int)len;
                if (len <= delta) {
                        /* Request is empty (only '\r\n', '\r' or '\n');
                         * delta is 2 ('\r\n') or 1 ('\r' or '\n'), see above */
                        array_moveleft(&My_Connections[Idx].rbuf, 1, len);
                        continue;
                }
#ifdef ZLIB
                /* remember if stream is already compressed */
                old_z = My_Connections[Idx].options & CONN_ZIP;
#endif

                My_Connections[Idx].msg_in++;
                if (!Parse_Request
                    (Idx, (char *)array_start(&My_Connections[Idx].rbuf)))
                        return 0; /* error -> connection has been closed */

                array_moveleft(&My_Connections[Idx].rbuf, 1, len);
#ifdef ZLIB
                if ((!old_z) && (My_Connections[Idx].options & CONN_ZIP) &&
                    (array_bytes(&My_Connections[Idx].rbuf) > 0)) {
                        /* The last command activated socket compression.
                         * Data that was read after that needs to be copied
                         * to the unzip buffer for decompression: */
                        if (!array_copy
                            (&My_Connections[Idx].zip.rbuf,
                             &My_Connections[Idx].rbuf)) {
                                Conn_Close(Idx, NULL,
                                           "Can't allocate memory [Handle_Buffer]",
                                           true);
                                return 0;
                        }

                        array_trunc(&My_Connections[Idx].rbuf);
                        LogDebug
                            ("Moved already received data (%u bytes) to uncompression buffer.",
                             array_bytes(&My_Connections[Idx].zip.rbuf));
                }
#endif
        }
#if DEBUG_BUFFER
        LogDebug("Connection %d: Processed %ld commands (max=%ld), %ld bytes. %ld bytes left in read buffer.",
                 Idx, i, maxcmd, len_processed,
                 array_bytes(&My_Connections[Idx].rbuf));
#endif

        /* If data has been processed but there is still data in the read
         * buffer, the command limit triggered. Enforce the penalty time: */
        if (len_processed && array_bytes(&My_Connections[Idx].rbuf) > 2)
                Throttle_Connection(Idx, c, THROTTLE_CMDS, maxcmd);

        return len_processed;
} /* Handle_Buffer */

/**
 * Check whether established connections are still alive or not.
 * If not, play PING-PONG first; and if that doesn't help either,
 * disconnect the respective peer.
 */
static void
Check_Connections(void)
{
        CLIENT *c;
        CONN_ID i;
        char msg[64];
        time_t time_now;

        time_now = time(NULL);

        for (i = 0; i < Pool_Size; i++) {
                if (My_Connections[i].sock < 0)
                        continue;

                c = Conn_GetClient(i);
                if (c && ((Client_Type(c) == CLIENT_USER)
                          || (Client_Type(c) == CLIENT_SERVER)
                          || (Client_Type(c) == CLIENT_SERVICE))) {
                        /* connected User, Server or Service */
                        if (My_Connections[i].lastping >
                            My_Connections[i].lastdata) {
                                /* We already sent a ping */
                                if (My_Connections[i].lastping <
                                    time_now - Conf_PongTimeout) {
                                        /* Timeout */
                                        snprintf(msg, sizeof(msg),
                                                 "Ping timeout: %d seconds",
                                                 Conf_PongTimeout);
                                        LogDebug("Connection %d: %s.", i, msg);
                                        Conn_Close(i, NULL, msg, true);
                                }
                        } else if (My_Connections[i].lastdata <
                                   time_now - Conf_PingTimeout) {
                                /* We need to send a PING ... */
                                LogDebug("Connection %d: sending PING ...", i);
                                Conn_UpdatePing(i, time_now);
                                Conn_WriteStr(i, "PING :%s",
                                              Client_ID(Client_ThisServer()));
                        }
                } else {
                        /* The connection is not fully established yet, so
                         * we don't do the PING-PONG game here but instead
                         * disconnect the client after "a short time" if it's
                         * still not registered. */

                        if (My_Connections[i].lastdata <
                            time_now - Conf_PongTimeout) {
                                LogDebug
                                    ("Unregistered connection %d timed out ...",
                                     i);
                                Conn_Close(i, NULL, "Timeout", false);
                        }
                }
        }
} /* Check_Connections */

/**
 * Check if further server links should be established.
 */
static void
Check_Servers(void)
{
        int i, n;
        time_t time_now;

        time_now = time(NULL);

        /* Check all configured servers */
        for (i = 0; i < MAX_SERVERS; i++) {
                if (Conf_Server[i].conn_id != NONE)
                        continue;       /* Already establishing or connected */
                if (!Conf_Server[i].host[0] || Conf_Server[i].port <= 0)
                        continue;       /* No host and/or port configured */
                if (Conf_Server[i].flags & CONF_SFLAG_DISABLED)
                        continue;       /* Disabled configuration entry */
                if (Conf_Server[i].lasttry > (time_now - Conf_ConnectRetry))
                        continue;       /* We have to wait a little bit ... */

                /* Is there already a connection in this group? */
                if (Conf_Server[i].group > NONE) {
                        for (n = 0; n < MAX_SERVERS; n++) {
                                if (n == i)
                                        continue;
                                if ((Conf_Server[n].conn_id != NONE) &&
                                    (Conf_Server[n].group == Conf_Server[i].group))
                                        break;
                        }
                        if (n < MAX_SERVERS)
                                continue;
                }

                /* Okay, try to connect now */
                Log(LOG_NOTICE,
                    "Preparing to establish a new server link for \"%s\" ...",
                    Conf_Server[i].name);
                Conf_Server[i].lasttry = time_now;
                Conf_Server[i].conn_id = SERVER_WAIT;
                assert(Proc_GetPipeFd(&Conf_Server[i].res_stat) < 0);

                /* Start resolver subprocess ... */
                if (!Resolve_Name(&Conf_Server[i].res_stat, Conf_Server[i].host,
                                  cb_Connect_to_Server))
                        Conf_Server[i].conn_id = NONE;
        }
} /* Check_Servers */

/**
 * Establish a new outgoing server connection.
 *
 * @param Server        Configuration index of the server.
 * @param dest          Destination IP address to connect to.
 */
static void
New_Server( int Server , ng_ipaddr_t *dest)
{
        /* Establish new server link */
        char ip_str[NG_INET_ADDRSTRLEN];
        int af_dest, res, new_sock;
        CLIENT *c;

        assert( Server > NONE );

        /* Make sure that the remote server hasn't re-linked to this server
         * asynchronously on its own */
        if (Conf_Server[Server].conn_id > NONE) {
                Log(LOG_INFO,
                        "Connection to \"%s\" meanwhile re-established, aborting preparation.");
                return;
        }

        if (!ng_ipaddr_tostr_r(dest, ip_str)) {
                Log(LOG_WARNING, "New_Server: Could not convert IP to string");
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        af_dest = ng_ipaddr_af(dest);
        new_sock = socket(af_dest, SOCK_STREAM, 0);

        Log(LOG_INFO,
            "Establishing connection for \"%s\" to \"%s:%d\" (%s), socket %d ...",
            Conf_Server[Server].name, Conf_Server[Server].host,
            Conf_Server[Server].port, ip_str, new_sock);

        if (new_sock < 0) {
                Log(LOG_CRIT, "Can't create socket (af %d): %s!",
                    af_dest, strerror(errno));
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        if (!Init_Socket(new_sock)) {
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        /* is a bind address configured? */
        res = ng_ipaddr_af(&Conf_Server[Server].bind_addr);

        /* if yes, bind now. If it fails, warn and let connect() pick a
         * source address */
        if (res && bind(new_sock, (struct sockaddr *) &Conf_Server[Server].bind_addr,
                                ng_ipaddr_salen(&Conf_Server[Server].bind_addr)))
        {
                ng_ipaddr_tostr_r(&Conf_Server[Server].bind_addr, ip_str);
                Log(LOG_WARNING, "Can't bind socket to %s: %s!", ip_str,
                    strerror(errno));
        }
        ng_ipaddr_setport(dest, Conf_Server[Server].port);
        res = connect(new_sock, (struct sockaddr *) dest, ng_ipaddr_salen(dest));
        if(( res != 0 ) && ( errno != EINPROGRESS )) {
                Log( LOG_CRIT, "Can't connect socket: %s!", strerror( errno ));
                close( new_sock );
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        if (Socket2Index(new_sock) <= NONE) {
                close( new_sock );
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        if (!io_event_create( new_sock, IO_WANTWRITE, cb_connserver)) {
                Log(LOG_ALERT, "io_event_create(): could not add fd %d",
                    strerror(errno));
                close(new_sock);
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        assert(My_Connections[new_sock].sock <= 0);

        Init_Conn_Struct(new_sock);

        ng_ipaddr_tostr_r(dest, ip_str);
        c = Client_NewLocal(new_sock, ip_str, CLIENT_UNKNOWNSERVER, false);
        if (!c) {
                Log( LOG_ALERT, "Can't establish connection: can't create client structure!" );
                io_close(new_sock);
                Conf_Server[Server].conn_id = NONE;
                return;
        }

        /* Conn_Close() decrements this counter again */
        Account_Connection();
        Client_SetIntroducer( c, c );
        Client_SetToken( c, TOKEN_OUTBOUND );

        /* Register connection */
        if (!Conf_SetServer(Server, new_sock))
                return;
        My_Connections[new_sock].sock = new_sock;
        My_Connections[new_sock].addr = *dest;
        My_Connections[new_sock].client = c;
        strlcpy( My_Connections[new_sock].host, Conf_Server[Server].host,
                                sizeof(My_Connections[new_sock].host ));

#ifdef SSL_SUPPORT
        if (Conf_Server[Server].SSLConnect &&
            !ConnSSL_PrepareConnect(&My_Connections[new_sock], &Conf_Server[Server]))
        {
                Log(LOG_ALERT, "Could not initialize SSL for outgoing connection");
                Conn_Close(new_sock, "Could not initialize SSL for outgoing connection",
                           NULL, false);
                Init_Conn_Struct(new_sock);
                Conf_Server[Server].conn_id = NONE;
                return;
        }
#endif
        LogDebug("Registered new connection %d on socket %d (%ld in total).",
                 new_sock, My_Connections[new_sock].sock, NumConnections);
        Conn_OPTION_ADD( &My_Connections[new_sock], CONN_ISCONNECTING );
} /* New_Server */

/**
 * Initialize connection structure.
 *
 * @param Idx   Connection index.
 */
static void
Init_Conn_Struct(CONN_ID Idx)
{
        time_t now = time(NULL);

        memset(&My_Connections[Idx], 0, sizeof(CONNECTION));
        My_Connections[Idx].sock = -1;
        My_Connections[Idx].signon = now;
        My_Connections[Idx].lastdata = now;
        My_Connections[Idx].lastprivmsg = now;
        Proc_InitStruct(&My_Connections[Idx].proc_stat);

#ifdef ICONV
        My_Connections[Idx].iconv_from = (iconv_t)(-1);
        My_Connections[Idx].iconv_to = (iconv_t)(-1);
#endif
} /* Init_Conn_Struct */

/**
 * Initialize options of a new socket.
 *
 * For example, we try to set socket options SO_REUSEADDR and IPTOS_LOWDELAY.
 * The socket is automatically closed if a fatal error is encountered.
 *
 * @param Sock  Socket handle.
 * @returns false if socket was closed due to fatal error.
 */
static bool
Init_Socket( int Sock )
{
        int value;

        if (!io_setnonblock(Sock)) {
                Log(LOG_CRIT, "Can't enable non-blocking mode for socket: %s!",
                    strerror(errno));
                close(Sock);
                return false;
        }

        /* Don't block this port after socket shutdown */
        value = 1;
        if (setsockopt(Sock, SOL_SOCKET, SO_REUSEADDR, &value,
                       (socklen_t)sizeof(value)) != 0) {
                Log(LOG_ERR, "Can't set socket option SO_REUSEADDR: %s!",
                    strerror(errno));
                /* ignore this error */
        }

        /* Set type of service (TOS) */
#if defined(IPPROTO_IP) && defined(IPTOS_LOWDELAY)
        value = IPTOS_LOWDELAY;
        if (setsockopt(Sock, IPPROTO_IP, IP_TOS, &value,
                       (socklen_t) sizeof(value))) {
                LogDebug("Can't set socket option IP_TOS: %s!",
                         strerror(errno));
                /* ignore this error */
        } else
                LogDebug("IP_TOS on socket %d has been set to IPTOS_LOWDELAY.",
                         Sock);
#endif

        return true;
} /* Init_Socket */

/**
 * Read results of a resolver sub-process and try to initiate a new server
 * connection.
 *
 * @param fd            File descriptor of the pipe to the sub-process.
 * @param events        (ignored IO specification)
 */
static void
cb_Connect_to_Server(int fd, UNUSED short events)
{
        int i;
        size_t len;

        /* we can handle at most 3 addresses; but we read up to 4 so we can
         * log the 'more than we can handle' condition. First result is tried
         * immediately, rest is saved for later if needed. */
        ng_ipaddr_t dest_addrs[4];

        LogDebug("Resolver: Got forward lookup callback on fd %d, events %d",
                 fd, events);

        for (i=0; i < MAX_SERVERS; i++) {
                  if (Proc_GetPipeFd(&Conf_Server[i].res_stat) == fd )
                          break;
        }

        if( i >= MAX_SERVERS) {
                /* Ops, no matching server found?! */
                io_close( fd );
                LogDebug("Resolver: Got Forward Lookup callback for unknown server!?");
                return;
        }

        /* Read result from pipe */
        len = Proc_Read(&Conf_Server[i].res_stat, dest_addrs, sizeof(dest_addrs));
        Proc_Close(&Conf_Server[i].res_stat);
        if (len == 0) {
                /* Error resolving hostname: reset server structure */
                Conf_Server[i].conn_id = NONE;
                return;
        }

        assert((len % sizeof(ng_ipaddr_t)) == 0);

        LogDebug("Got result from resolver: %u structs (%u bytes).",
                 len/sizeof(ng_ipaddr_t), len);

        memset(&Conf_Server[i].dst_addr, 0, sizeof(Conf_Server[i].dst_addr));
        if (len > sizeof(ng_ipaddr_t)) {
                /* more than one address for this hostname, remember them
                 * in case first address is unreachable/not available */
                len -= sizeof(ng_ipaddr_t);
                if (len > sizeof(Conf_Server[i].dst_addr)) {
                        len = sizeof(Conf_Server[i].dst_addr);
                        Log(LOG_NOTICE,
                                "Notice: Resolver returned more IP Addresses for host than we can handle, additional addresses dropped.");
                }
                memcpy(&Conf_Server[i].dst_addr, &dest_addrs[1], len);
        }
        /* connect() */
        New_Server(i, dest_addrs);
} /* cb_Read_Forward_Lookup */

/**
 * Read results of a resolver sub-process from the pipe and update the
 * appropriate connection/client structure(s): hostname and/or IDENT user name.
 *
 * @param r_fd          File descriptor of the pipe to the sub-process.
 * @param events        (ignored IO specification)
 */
static void
cb_Read_Resolver_Result( int r_fd, UNUSED short events )
{
        CLIENT *c;
        CONN_ID i;
        size_t len;
        char *identptr;
#ifdef IDENTAUTH
        char readbuf[HOST_LEN + 2 + CLIENT_USER_LEN];
        char *ptr;
#else
        char readbuf[HOST_LEN + 1];
#endif

        LogDebug("Resolver: Got callback on fd %d, events %d", r_fd, events );
        i = Conn_GetFromProc(r_fd);
        if (i == NONE) {
                /* Ops, none found? Probably the connection has already
                 * been closed!? We'll ignore that ... */
                io_close( r_fd );
                LogDebug("Resolver: Got callback for unknown connection!?");
                return;
        }

        /* Read result from pipe */
        len = Proc_Read(&My_Connections[i].proc_stat, readbuf, sizeof readbuf -1);
        Proc_Close(&My_Connections[i].proc_stat);
        if (len == 0)
                return;

        readbuf[len] = '\0';
        identptr = strchr(readbuf, '\n');
        assert(identptr != NULL);
        if (!identptr) {
                Log( LOG_CRIT, "Resolver: Got malformed result!");
                return;
        }

        *identptr = '\0';
        LogDebug("Got result from resolver: \"%s\" (%u bytes read).", readbuf, len);
        /* Okay, we got a complete result: this is a host name for outgoing
         * connections and a host name and IDENT user name (if enabled) for
         * incoming connections.*/
        assert ( My_Connections[i].sock >= 0 );
        /* Incoming connection. Search client ... */
        c = Conn_GetClient( i );
        assert( c != NULL );

        /* Only update client information of unregistered clients.
         * Note: user commands (e. g. WEBIRC) are always read _after_ reading
         * the resolver results, so we don't have to worry to override settings
         * from these commands here. */
        if(Client_Type(c) == CLIENT_UNKNOWN) {
                if (readbuf[0]) {
                        /* We got a hostname */
                        strlcpy(My_Connections[i].host, readbuf,
                                sizeof(My_Connections[i].host));
                        Client_SetHostname(c, readbuf);
                        if (Conf_NoticeBeforeRegistration)
                                (void)Conn_WriteStr(i,
                                        "NOTICE * :*** Found your hostname: %s",
                                        My_Connections[i].host);
                }
#ifdef IDENTAUTH
                ++identptr;
                if (*identptr) {
                        ptr = identptr;
                        while (*ptr) {
                                if ((*ptr < '0' || *ptr > '9') &&
                                    (*ptr < 'A' || *ptr > 'Z') &&
                                    (*ptr < 'a' || *ptr > 'z'))
                                        break;
                                ptr++;
                        }
                        if (*ptr) {
                                /* Erroneous IDENT reply */
                                Log(LOG_NOTICE,
                                    "Got invalid IDENT reply for connection %d! Ignored.",
                                    i);
                        } else {
                                Log(LOG_INFO,
                                    "IDENT lookup for connection %d: \"%s\".",
                                    i, identptr);
                                Client_SetUser(c, identptr, true);
                        }
                        if (Conf_NoticeBeforeRegistration) {
                                (void)Conn_WriteStr(i,
                                        "NOTICE * :*** Got %sident response%s%s",
                                        *ptr ? "invalid " : "",
                                        *ptr ? "" : ": ",
                                        *ptr ? "" : identptr);
                        }
                } else if(Conf_Ident) {
                        Log(LOG_INFO, "IDENT lookup for connection %d: no result.", i);
                        if (Conf_NoticeBeforeRegistration)
                                (void)Conn_WriteStr(i,
                                        "NOTICE * :*** No ident response");
                }
#endif

                if (Conf_NoticeBeforeRegistration) {
                        /* Send buffered data to the client, but break on
                         * errors because Handle_Write() would have closed
                         * the connection again in this case! */
                        if (!Handle_Write(i))
                                return;
                }

                Class_HandleServerBans(c);
        }
        else
                LogDebug("Resolver: discarding result for already registered connection %d.", i);
} /* cb_Read_Resolver_Result */

/**
 * Write a "simple" (error) message to a socket.
 *
 * The message is sent without using the connection write buffers, without
 * compression/encryption, and even without any error reporting. It is
 * designed for error messages of e.g. New_Connection().
 *
 * @param Sock  Socket handle.
 * @param Msg   Message string to send.
 */
static void
Simple_Message(int Sock, const char *Msg)
{
        char buf[COMMAND_LEN];
        size_t len;

        assert(Sock > NONE);
        assert(Msg != NULL);

        strlcpy(buf, Msg, sizeof buf - 2);
        len = strlcat(buf, "\r\n", sizeof buf);
        if (write(Sock, buf, len) < 0) {
                /* Because this function most probably got called to log
                 * an error message, any write error is ignored here to
                 * avoid an endless loop. But casting the result of write()
                 * to "void" doesn't satisfy the GNU C code attribute
                 * "warn_unused_result" which is used by some versions of
                 * glibc (e.g. 2.11.1), therefore this silly error
                 * "handling" code here :-( */
                return;
        }
} /* Simple_Error */

/**
 * Get CLIENT structure that belongs to a local connection identified by its
 * index number. Each connection belongs to a client by definition, so it is
 * not required that the caller checks for NULL return values.
 *
 * @param Idx   Connection index number.
 * @returns     Pointer to CLIENT structure.
 */
GLOBAL CLIENT *
Conn_GetClient( CONN_ID Idx )
{
        CONNECTION *c;

        assert(Idx >= 0);
        c = array_get(&My_ConnArray, sizeof (CONNECTION), (size_t)Idx);
        assert(c != NULL);
        return c ? c->client : NULL;
}

/**
 * Get PROC_STAT sub-process structure of a connection.
 *
 * @param Idx   Connection index number.
 * @returns     PROC_STAT structure.
 */
GLOBAL PROC_STAT *
Conn_GetProcStat(CONN_ID Idx)
{
        CONNECTION *c;

        assert(Idx >= 0);
        c = array_get(&My_ConnArray, sizeof (CONNECTION), (size_t)Idx);
        assert(c != NULL);
        return &c->proc_stat;
} /* Conn_GetProcStat */

/**
 * Get CONN_ID from file descriptor associated to a subprocess structure.
 *
 * @param fd    File descriptor.
 * @returns     CONN_ID or NONE (-1).
 */
GLOBAL CONN_ID
Conn_GetFromProc(int fd)
{
        int i;

        assert(fd > 0);
        for (i = 0; i < Pool_Size; i++) {
                if ((My_Connections[i].sock != NONE)
                    && (Proc_GetPipeFd(&My_Connections[i].proc_stat) == fd))
                        return i;
        }
        return NONE;
} /* Conn_GetFromProc */

/**
 * Throttle a connection because of excessive usage.
 *
 * @param Reason The reason, see THROTTLE_xxx constants.
 * @param Idx The connection index.
 * @param Client The client of this connection.
 * @param Value The time to delay this connection.
 */
static void
Throttle_Connection(const CONN_ID Idx, CLIENT *Client, const int Reason,
                    unsigned int Value)
{
        assert(Idx > NONE);
        assert(Client != NULL);

        /* Never throttle servers or services, only interrupt processing */
        if (Client_Type(Client) == CLIENT_SERVER
            || Client_Type(Client) == CLIENT_UNKNOWNSERVER
            || Client_Type(Client) == CLIENT_SERVICE)
                return;

        /* Don't throttle clients with user mode 'F' set */
        if (Client_HasMode(Client, 'F'))
                return;

        LogDebug("Throttling connection %d: code %d, value %d!", Idx,
                 Reason, Value);
        Conn_SetPenalty(Idx, 1);
}

#ifndef STRICT_RFC

GLOBAL long
Conn_GetAuthPing(CONN_ID Idx)
{
        assert (Idx != NONE);
        return My_Connections[Idx].auth_ping;
} /* Conn_GetAuthPing */

GLOBAL void
Conn_SetAuthPing(CONN_ID Idx, long ID)
{
        assert (Idx != NONE);
        My_Connections[Idx].auth_ping = ID;
} /* Conn_SetAuthPing */

#endif /* STRICT_RFC */

#ifdef SSL_SUPPORT

/**
 * IO callback for new SSL-enabled client and server connections.
 *
 * @param sock  Socket descriptor.
 * @param what  IO specification (IO_WANTREAD/IO_WANTWRITE/...).
 */
static void
cb_clientserver_ssl(int sock, UNUSED short what)
{
        CONN_ID idx = Socket2Index(sock);

        if (idx <= NONE) {
                io_close(sock);
                return;
        }

        switch (ConnSSL_Accept(&My_Connections[idx])) {
                case 1:
                        break;  /* OK */
                case 0:
                        return; /* EAGAIN: callback will be invoked again by IO layer */
                default:
                        Conn_Close(idx,
                                   "SSL accept error, closing socket", "SSL accept error",
                                   false);
                        return;
        }

        io_event_setcb(sock, cb_clientserver);  /* SSL handshake completed */
}

/**
 * IO callback for listening SSL sockets: handle new connections. This callback
 * gets called when a new SSL-enabled connection should be accepted.
 *
 * @param sock          Socket descriptor.
 * @param irrelevant    (ignored IO specification)
 */
static void
cb_listen_ssl(int sock, short irrelevant)
{
        int fd;

        (void) irrelevant;
        fd = New_Connection(sock, true);
        if (fd < 0)
                return;
        io_event_setcb(My_Connections[fd].sock, cb_clientserver_ssl);
}

/**
 * IO callback for new outgoing SSL-enabled server connections.
 *
 * IMPORTANT: The SSL session has been validated before, but all errors have
 * been ignored so far! The reason for this is that the generic SSL code has no
 * idea if the new session actually belongs to a server, as this only becomes
 * clear when the remote peer sends its PASS command (and we have to handle
 * invalid client certificates!). Therefore, it is important to check the
 * status of the SSL session first before continuing the server handshake here!
 *
 * @param sock          Socket descriptor.
 * @param unused        (ignored IO specification)
 */
static void
cb_connserver_login_ssl(int sock, short unused)
{
        CONN_ID idx = Socket2Index(sock);
        int serveridx;

        (void) unused;

        if (idx <= NONE) {
                io_close(sock);
                return;
        }

        switch (ConnSSL_Connect( &My_Connections[idx])) {
                case 1: break;
                case 0: LogDebug("ConnSSL_Connect: not ready");
                        return;
                case -1:
                        Log(LOG_ERR, "SSL connection on socket %d failed!", sock);
                        Conn_Close(idx, "Can't connect", NULL, false);
                        return;
        }

        serveridx = Conf_GetServer(idx);
        assert(serveridx >= 0);

        /* The SSL handshake is done, but validation results were ignored so
         * far, so let's see where we are: */
        LogDebug("SSL handshake on socket %d done.", idx);
        if (!Conn_OPTION_ISSET(&My_Connections[idx], CONN_SSL_PEERCERT_OK)) {
                if (Conf_Server[serveridx].SSLVerify) {
                        Log(LOG_ERR,
                                "Peer certificate check failed for \"%s\" on connection %d!",
                                My_Connections[idx].host, idx);
                        Conn_Close(idx, "Valid certificate required",
                                   NULL, false);
                        return;
                }
                Log(LOG_WARNING,
                        "Peer certificate check failed for \"%s\" on connection %d, but \"SSLVerify\" is disabled. Continuing ...",
                        My_Connections[idx].host, idx);
        }
        LogDebug("Server certificate accepted, continuing server login ...");
        server_login(idx);
}


/**
 * Check if SSL library needs to read SSL-protocol related data.
 *
 * SSL/TLS connections require extra treatment:
 * When either CONN_SSL_WANT_WRITE or CONN_SSL_WANT_READ is set, we
 * need to take care of that first, before checking read/write buffers.
 * For instance, while we might have data in our write buffer, the
 * TLS/SSL protocol might need to read internal data first for TLS/SSL
 * writes to succeed.
 *
 * If this function returns true, such a condition is met and we have
 * to reverse the condition (check for read even if we've data to write,
 * do not check for read but writeability even if write-buffer is empty).
 *
 * @param c     Connection to check.
 * @returns     true if SSL-library has to read protocol data.
 */
static bool
SSL_WantRead(const CONNECTION *c)
{
        if (Conn_OPTION_ISSET(c, CONN_SSL_WANT_READ)) {
                io_event_add(c->sock, IO_WANTREAD);
                return true;
        }
        return false;
}

/**
 * Check if SSL library needs to write SSL-protocol related data.
 *
 * Please see description of SSL_WantRead() for full description!
 *
 * @param c     Connection to check.
 * @returns     true if SSL-library has to write protocol data.
 */
static bool
SSL_WantWrite(const CONNECTION *c)
{
        if (Conn_OPTION_ISSET(c, CONN_SSL_WANT_WRITE)) {
                io_event_add(c->sock, IO_WANTWRITE);
                return true;
        }
        return false;
}

/**
 * Get information about used SSL cipher.
 *
 * @param Idx   Connection index number.
 * @param buf   Buffer for returned information text.
 * @param len   Size of return buffer "buf".
 * @returns     true on success, false otherwise.
 */
GLOBAL bool
Conn_GetCipherInfo(CONN_ID Idx, char *buf, size_t len)
{
        if (Idx < 0)
                return false;
        assert(Idx < (int) array_length(&My_ConnArray, sizeof(CONNECTION)));
        return ConnSSL_GetCipherInfo(&My_Connections[Idx], buf, len);
}

/**
 * Check if a connection is SSL-enabled or not.
 *
 * @param Idx   Connection index number.
 * @return      true if connection is SSL-enabled, false otherwise.
 */
GLOBAL bool
Conn_UsesSSL(CONN_ID Idx)
{
        if (Idx < 0)
                return false;
        assert(Idx < (int) array_length(&My_ConnArray, sizeof(CONNECTION)));
        return Conn_OPTION_ISSET(&My_Connections[Idx], CONN_SSL);
}

GLOBAL char *
Conn_GetCertFp(CONN_ID Idx)
{
        if (Idx < 0)
                return NULL;
        assert(Idx < (int) array_length(&My_ConnArray, sizeof(CONNECTION)));
        return ConnSSL_GetCertFp(&My_Connections[Idx]);
}

GLOBAL bool
Conn_SetCertFp(CONN_ID Idx, const char *fingerprint)
{
        if (Idx < 0)
                return false;
        assert(Idx < (int) array_length(&My_ConnArray, sizeof(CONNECTION)));
        return ConnSSL_SetCertFp(&My_Connections[Idx], fingerprint);
}

#else /* SSL_SUPPORT */

GLOBAL bool
Conn_UsesSSL(UNUSED CONN_ID Idx)
{
        return false;
}

GLOBAL char *
Conn_GetCertFp(UNUSED CONN_ID Idx)
{
        return NULL;
}

GLOBAL bool
Conn_SetCertFp(UNUSED CONN_ID Idx, UNUSED const char *fingerprint)
{
        return true;
}

#endif /* SSL_SUPPORT */


/**
 * Dump internal state of the "connection module".
 */
GLOBAL void
Conn_DebugDump(void)
{
        int i;

        LogDebug("Connection status:");
        for (i = 0; i < Pool_Size; i++) {
                if (My_Connections[i].sock == NONE)
                        continue;
                LogDebug(
                    " - %d: host=%s, lastdata=%ld, lastping=%ld, delaytime=%ld, flag=%d, options=%d, bps=%d, client=%s",
                    My_Connections[i].sock, My_Connections[i].host,
                    My_Connections[i].lastdata, My_Connections[i].lastping,
                    My_Connections[i].delaytime, My_Connections[i].flag,
                    My_Connections[i].options, My_Connections[i].bps,
                    My_Connections[i].client ? Client_ID(My_Connections[i].client) : "-");
        }
} /* Conn_DumpClients */


/* -eof- */