libevent/sample/dns-example.c

   1 /*
   2   This example code shows how to use the high-level, low-level, and
   3   server-level interfaces of evdns.
   4
   5   XXX It's pretty ugly and should probably be cleaned up.
   6  */
   7
   8 #include <event2/event-config.h>
   9
  10 #include <sys/types.h>
  11
  12 #ifdef WIN32
  13 #include <winsock2.h>
  14 #include <ws2tcpip.h>
  15 #else
  16 #include <sys/socket.h>
  17 #include <netinet/in.h>
  18 #include <arpa/inet.h>
  19 #endif
  20
  21 #include <event2/event.h>
  22 #include <event2/dns.h>
  23 #include <event2/dns_struct.h>
  24 #include <event2/util.h>
  25
  26 #ifdef _EVENT_HAVE_NETINET_IN6_H
  27 #include <netinet/in6.h>
  28 #endif
  29
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #define u32 ev_uint32_t
  35 #define u8 ev_uint8_t
  36
  37 static const char *
  38 debug_ntoa(u32 address)
  39 {
  40         static char buf[32];
  41         u32 a = ntohl(address);
  42         evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
  43                                         (int)(u8)((a>>24)&0xff),
  44                                         (int)(u8)((a>>16)&0xff),
  45                                         (int)(u8)((a>>8 )&0xff),
  46                                         (int)(u8)((a    )&0xff));
  47         return buf;
  48 }
  49
  50 static void
  51 main_callback(int result, char type, int count, int ttl,
  52                           void *addrs, void *orig) {
  53         char *n = (char*)orig;
  54         int i;
  55         for (i = 0; i < count; ++i) {
  56                 if (type == DNS_IPv4_A) {
  57                         printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i]));
  58                 } else if (type == DNS_PTR) {
  59                         printf("%s: %s\n", n, ((char**)addrs)[i]);
  60                 }
  61         }
  62         if (!count) {
  63                 printf("%s: No answer (%d)\n", n, result);
  64         }
  65         fflush(stdout);
  66 }
  67
  68 static void
  69 gai_callback(int err, struct evutil_addrinfo *ai, void *arg)
  70 {
  71         const char *name = arg;
  72         struct evutil_addrinfo *ai_first = NULL;
  73         int i;
  74         if (err) {
  75                 printf("%s: %s\n", name, evutil_gai_strerror(err));
  76         }
  77         if (ai && ai->ai_canonname)
  78                 printf("    %s ==> %s\n", name, ai->ai_canonname);
  79         for (i=0; ai; ai = ai->ai_next, ++i) {
  80                 char buf[128];
  81                 if (ai->ai_family == PF_INET) {
  82                         struct sockaddr_in *sin =
  83                             (struct sockaddr_in*)ai->ai_addr;
  84                         evutil_inet_ntop(AF_INET, &sin->sin_addr, buf,
  85                             sizeof(buf));
  86                         printf("[%d] %s: %s\n",i,name,buf);
  87                 } else {
  88                         struct sockaddr_in6 *sin6 =
  89                             (struct sockaddr_in6*)ai->ai_addr;
  90                         evutil_inet_ntop(AF_INET6, &sin6->sin6_addr, buf,
  91                             sizeof(buf));
  92                         printf("[%d] %s: %s\n",i,name,buf);
  93                 }
  94         }
  95         if (ai_first)
  96                 evutil_freeaddrinfo(ai_first);
  97 }
  98
  99 static void
 100 evdns_server_callback(struct evdns_server_request *req, void *data)
 101 {
 102         int i, r;
 103         (void)data;
 104         /* dummy; give 192.168.11.11 as an answer for all A questions,
 105          *      give foo.bar.example.com as an answer for all PTR questions. */
 106         for (i = 0; i < req->nquestions; ++i) {
 107                 u32 ans = htonl(0xc0a80b0bUL);
 108                 if (req->questions[i]->type == EVDNS_TYPE_A &&
 109                     req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
 110                         printf(" -- replying for %s (A)\n", req->questions[i]->name);
 111                         r = evdns_server_request_add_a_reply(req, req->questions[i]->name,
 112                                                                                   1, &ans, 10);
 113                         if (r<0)
 114                                 printf("eeep, didn't work.\n");
 115                 } else if (req->questions[i]->type == EVDNS_TYPE_PTR &&
 116                     req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
 117                         printf(" -- replying for %s (PTR)\n", req->questions[i]->name);
 118                         r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name,
 119                                                                                         "foo.bar.example.com", 10);
 120                 } else {
 121                         printf(" -- skipping %s [%d %d]\n", req->questions[i]->name,
 122                                    req->questions[i]->type, req->questions[i]->dns_question_class);
 123                 }
 124         }
 125
 126         r = evdns_server_request_respond(req, 0);
 127         if (r<0)
 128                 printf("eeek, couldn't send reply.\n");
 129 }
 130
 131 static int verbose = 0;
 132
 133 static void
 134 logfn(int is_warn, const char *msg) {
 135         if (!is_warn && !verbose)
 136                 return;
 137         fprintf(stderr, "%s: %s\n", is_warn?"WARN":"INFO", msg);
 138 }
 139
 140 int
 141 main(int c, char **v) {
 142         int idx;
 143         int reverse = 0, servertest = 0, use_getaddrinfo = 0;
 144         struct event_base *event_base = NULL;
 145         struct evdns_base *evdns_base = NULL;
 146         if (c<2) {
 147                 fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]);
 148                 fprintf(stderr, "syntax: %s [-servertest]\n", v[0]);
 149                 return 1;
 150         }
 151         idx = 1;
 152         while (idx < c && v[idx][0] == '-') {
 153                 if (!strcmp(v[idx], "-x"))
 154                         reverse = 1;
 155                 else if (!strcmp(v[idx], "-v"))
 156                         verbose = 1;
 157                 else if (!strcmp(v[idx], "-g"))
 158                         use_getaddrinfo = 1;
 159                 else if (!strcmp(v[idx], "-servertest"))
 160                         servertest = 1;
 161                 else
 162                         fprintf(stderr, "Unknown option %s\n", v[idx]);
 163                 ++idx;
 164         }
 165
 166         event_base = event_base_new();
 167         evdns_base = evdns_base_new(event_base, 0);
 168         evdns_set_log_fn(logfn);
 169
 170         if (servertest) {
 171                 evutil_socket_t sock;
 172                 struct sockaddr_in my_addr;
 173                 sock = socket(PF_INET, SOCK_DGRAM, 0);
 174                 evutil_make_socket_nonblocking(sock);
 175                 my_addr.sin_family = AF_INET;
 176                 my_addr.sin_port = htons(10053);
 177                 my_addr.sin_addr.s_addr = INADDR_ANY;
 178                 if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) {
 179                         perror("bind");
 180                         exit(1);
 181                 }
 182                 evdns_add_server_port_with_base(event_base, sock, 0, evdns_server_callback, NULL);
 183         }
 184         if (idx < c) {
 185 #ifdef WIN32
 186                 evdns_base_config_windows_nameservers(evdns_base);
 187 #else
 188                 evdns_base_resolv_conf_parse(evdns_base, DNS_OPTION_NAMESERVERS,
 189                     "/etc/resolv.conf");
 190 #endif
 191         }
 192
 193         printf("EVUTIL_AI_CANONNAME in example = %d\n", EVUTIL_AI_CANONNAME);
 194         for (; idx < c; ++idx) {
 195                 if (reverse) {
 196                         struct in_addr addr;
 197                         if (evutil_inet_pton(AF_INET, v[idx], &addr)!=1) {
 198                                 fprintf(stderr, "Skipping non-IP %s\n", v[idx]);
 199                                 continue;
 200                         }
 201                         fprintf(stderr, "resolving %s...\n",v[idx]);
 202                         evdns_base_resolve_reverse(evdns_base, &addr, 0, main_callback, v[idx]);
 203                 } else if (use_getaddrinfo) {
 204                         struct evutil_addrinfo hints;
 205                         memset(&hints, 0, sizeof(hints));
 206                         hints.ai_family = PF_UNSPEC;
 207                         hints.ai_protocol = IPPROTO_TCP;
 208                         hints.ai_flags = EVUTIL_AI_CANONNAME;
 209                         fprintf(stderr, "resolving (fwd) %s...\n",v[idx]);
 210                         evdns_getaddrinfo(evdns_base, v[idx], NULL, &hints,
 211                             gai_callback, v[idx]);
 212                 } else {
 213                         fprintf(stderr, "resolving (fwd) %s...\n",v[idx]);
 214                         evdns_base_resolve_ipv4(evdns_base, v[idx], 0, main_callback, v[idx]);
 215                 }
 216         }
 217         fflush(stdout);
 218         event_base_dispatch(event_base);
 219         return 0;
 220 }
 221