Implement support for systemd(8) "socket activation"

This patch enables ngIRCd to work with listening sockets already
initialized and passed-in by systemd(8) and hereby to support on-demand
"socket activation".

systemd(8) uses two environment variables to pass information about the
sockets to ngIRCd, LISTEN_PID and LISTEN_FDS, and this mechanism only
kicks in when both variables are set. In all other cases, and therefore
in most installations out there, nothing changes at all.

Please note:
If socket activation is in effect, ngIRCd will not initialize any (other)
soeckets on its own! All sockets must be configured in the systemd(8)
socket unit configuration file in this case, see ./contrib/ngircd.socket
for example.

Probably it would be interesting to match passed-in sockets to configured
listening sockets and to initialize all the remaining ones not already
set up by systemd(8), but this is kept back for an other patch ...

See
 - <http://0pointer.de/blog/projects/socket-activation.html>
 - <http://0pointer.de/blog/projects/socket-activation2.html>
 - <http://www.freedesktop.org/software/systemd/man/systemd.socket.html>

diff --git a/contrib/Makefile.am b/contrib/Makefile.am
index 09b43a68a8bb71ef5ba2fb3dd02f9cee1f04bf14..6d16f7cac50f8b177fb4d336201906733b0a3607 100644 (file)
--- a/contrib/Makefile.am
+++ b/contrib/Makefile.am
@@ -1,6 +1,6 @@
 #
 # ngIRCd -- The Next Generation IRC Daemon
-# Copyright (c)2001-2012 Alexander Barton (alex@barton.de) and Contributors
+# Copyright (c)2001-2013 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
@@ -17,6 +17,7 @@ EXTRA_DIST = README \
        ngIRCd-Logo.gif \
        ngircd-redhat.init \
        ngircd.service \
+       ngircd.socket \
        ngircd.spec \
        platformtest.sh \
        systrace.policy

diff --git a/contrib/README b/contrib/README
index f3730a4e969c69aed07bbfdfb737a7901b382fa8..2d639e664076d19c8b20a23e50a4d6426ddd6953 100644 (file)
--- a/contrib/README
+++ b/contrib/README
@@ -30,6 +30,9 @@ ngircd-redhat.init
 ngircd.service
  - systemd(8) service unit configuration file.
 
+ngircd.socket
+ - systemd(8) socket unit configuration file for "socket activation".
+
 ngircd.spec
  - RPM "spec" file.
 

diff --git a/contrib/ngircd.socket b/contrib/ngircd.socket
new file mode 100644 (file)
index 0000000..3838efc
--- /dev/null
+++ b/contrib/ngircd.socket
@@ -0,0 +1,10 @@
+[Unit]
+Description=Next Generation IRC Daemon (Socket)
+
+[Socket]
+ListenStream=6667
+#ListenStream=6668
+IPTOS=low-delay
+
+[Install]
+WantedBy=sockets.target

diff --git a/src/ngircd/conn.c b/src/ngircd/conn.c
index 14d337b9408265b1213a157cd36cf66a8efc057e..378509f96f09bc35eb9e3ebc2eb12140c24509fb 100644 (file)
--- a/src/ngircd/conn.c
+++ b/src/ngircd/conn.c
@@ -82,6 +82,8 @@
 #define MAX_COMMANDS_SERVER_MIN 10
 #define MAX_COMMANDS_SERVICE 10
 
+#define SD_LISTEN_FDS_START 3
+
 
 static bool Handle_Write PARAMS(( CONN_ID Idx ));
 static bool Conn_Write PARAMS(( CONN_ID Idx, char *Data, size_t Len ));
@@ -120,6 +122,40 @@ static void cb_Connect_to_Server PARAMS((int sock, UNUSED short what));
 static void cb_clientserver PARAMS((int sock, short what));
 
 
+/**
+ * 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, becaus 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;
+       long 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 = atol(e);
+       unsetenv("LISTEN_FDS");
+
+       return count;
+}
+
+
 /**
  * IO callback for listening sockets: handle new connections. This callback
  * gets called when a new non-SSL connection should be accepted.
@@ -495,9 +531,38 @@ Conn_InitListeners( void )
        /* Initialize ports on which the server should accept connections */
        unsigned int created = 0;
        char *copy, *listen_addr;
+       int count, fd, i;
 
        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;
+                       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.", fd);
+                       created++;
+               }
+               return created;
+       }
+
+       /* not using systemd socket activation, initialize listening sockets: */
+
        /* can't use Conf_ListenAddress directly, see below */
        copy = strdup(Conf_ListenAddress);
        if (!copy) {
@@ -541,7 +606,12 @@ Conn_ExitListeners( void )
        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);