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 /* Compatibility for possible missing IPv6 declarations */
  11 #include "../ipv6-internal.h"
  12
  13 #include <sys/types.h>
  14
  15 #ifdef EVENT__HAVE_UNISTD_H
  16 #include <unistd.h>
  17 #endif
  18
  19 #ifdef _WIN32
  20 #include <winsock2.h>
  21 #include <ws2tcpip.h>
  22 #include <getopt.h>
  23 #else
  24 #include <sys/socket.h>
  25 #include <netinet/in.h>
  26 #include <arpa/inet.h>
  27 #endif
  28
  29 #include <event2/event.h>
  30 #include <event2/dns.h>
  31 #include <event2/dns_struct.h>
  32 #include <event2/util.h>
  33
  34 #ifdef EVENT__HAVE_NETINET_IN6_H
  35 #include <netinet/in6.h>
  36 #endif
  37
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41
  42 #define u32 ev_uint32_t
  43 #define u8 ev_uint8_t
  44
  45 static const char *
  46 debug_ntoa(u32 address)
  47 {
  48         static char buf[32];
  49         u32 a = ntohl(address);
  50         evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
  51                                         (int)(u8)((a>>24)&0xff),
  52                                         (int)(u8)((a>>16)&0xff),
  53                                         (int)(u8)((a>>8 )&0xff),
  54                                         (int)(u8)((a    )&0xff));
  55         return buf;
  56 }
  57
  58 static void
  59 main_callback(int result, char type, int count, int ttl,
  60                           void *addrs, void *orig) {
  61         char *n = (char*)orig;
  62         int i;
  63         for (i = 0; i < count; ++i) {
  64                 if (type == DNS_IPv4_A) {
  65                         printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i]));
  66                 } else if (type == DNS_PTR) {
  67                         printf("%s: %s\n", n, ((char**)addrs)[i]);
  68                 }
  69         }
  70         if (!count) {
  71                 printf("%s: No answer (%d)\n", n, result);
  72         }
  73         fflush(stdout);
  74 }
  75
  76 static void
  77 gai_callback(int err, struct evutil_addrinfo *ai, void *arg)
  78 {
  79         const char *name = arg;
  80         int i;
  81         struct evutil_addrinfo *first_ai = ai;
  82
  83         if (err) {
  84                 printf("%s: %s\n", name, evutil_gai_strerror(err));
  85         }
  86         if (ai && ai->ai_canonname)
  87                 printf("    %s ==> %s\n", name, ai->ai_canonname);
  88         for (i=0; ai; ai = ai->ai_next, ++i) {
  89                 char buf[128];
  90                 if (ai->ai_family == PF_INET) {
  91                         struct sockaddr_in *sin =
  92                             (struct sockaddr_in*)ai->ai_addr;
  93                         evutil_inet_ntop(AF_INET, &sin->sin_addr, buf,
  94                             sizeof(buf));
  95                         printf("[%d] %s: %s\n",i,name,buf);
  96                 } else {
  97                         struct sockaddr_in6 *sin6 =
  98                             (struct sockaddr_in6*)ai->ai_addr;
  99                         evutil_inet_ntop(AF_INET6, &sin6->sin6_addr, buf,
 100                             sizeof(buf));
 101                         printf("[%d] %s: %s\n",i,name,buf);
 102                 }
 103         }
 104
 105         if (first_ai)
 106                 evutil_freeaddrinfo(first_ai);
 107 }
 108
 109 static void
 110 evdns_server_callback(struct evdns_server_request *req, void *data)
 111 {
 112         int i, r;
 113         (void)data;
 114         /* dummy; give 192.168.11.11 as an answer for all A questions,
 115          *      give foo.bar.example.com as an answer for all PTR questions. */
 116         for (i = 0; i < req->nquestions; ++i) {
 117                 u32 ans = htonl(0xc0a80b0bUL);
 118                 if (req->questions[i]->type == EVDNS_TYPE_A &&
 119                     req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
 120                         printf(" -- replying for %s (A)\n", req->questions[i]->name);
 121                         r = evdns_server_request_add_a_reply(req, req->questions[i]->name,
 122                                                                                   1, &ans, 10);
 123                         if (r<0)
 124                                 printf("eeep, didn't work.\n");
 125                 } else if (req->questions[i]->type == EVDNS_TYPE_PTR &&
 126                     req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
 127                         printf(" -- replying for %s (PTR)\n", req->questions[i]->name);
 128                         r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name,
 129                                                                                         "foo.bar.example.com", 10);
 130                         if (r<0)
 131                                 printf("ugh, no luck");
 132                 } else {
 133                         printf(" -- skipping %s [%d %d]\n", req->questions[i]->name,
 134                                    req->questions[i]->type, req->questions[i]->dns_question_class);
 135                 }
 136         }
 137
 138         r = evdns_server_request_respond(req, 0);
 139         if (r<0)
 140                 printf("eeek, couldn't send reply.\n");
 141 }
 142
 143 static int verbose = 0;
 144
 145 static void
 146 logfn(int is_warn, const char *msg) {
 147         if (!is_warn && !verbose)
 148                 return;
 149         fprintf(stderr, "%s: %s\n", is_warn?"WARN":"INFO", msg);
 150 }
 151
 152 int
 153 main(int c, char **v) {
 154         struct options {
 155                 int reverse;
 156                 int use_getaddrinfo;
 157                 int servertest;
 158                 const char *resolv_conf;
 159                 const char *ns;
 160         };
 161         struct options o;
 162         int opt;
 163         struct event_base *event_base = NULL;
 164         struct evdns_base *evdns_base = NULL;
 165
 166         memset(&o, 0, sizeof(o));
 167
 168         if (c < 2) {
 169                 fprintf(stderr, "syntax: %s [-x] [-v] [-c resolv.conf] [-s ns] hostname\n", v[0]);
 170                 fprintf(stderr, "syntax: %s [-T]\n", v[0]);
 171                 return 1;
 172         }
 173
 174         while ((opt = getopt(c, v, "xvc:Ts:g")) != -1) {
 175                 switch (opt) {
 176                         case 'x': o.reverse = 1; break;
 177                         case 'v': ++verbose; break;
 178                         case 'g': o.use_getaddrinfo = 1; break;
 179                         case 'T': o.servertest = 1; break;
 180                         case 'c': o.resolv_conf = optarg; break;
 181                         case 's': o.ns = optarg; break;
 182                         default : fprintf(stderr, "Unknown option %c\n", opt); break;
 183                 }
 184         }
 185
 186 #ifdef _WIN32
 187         {
 188                 WSADATA WSAData;
 189                 WSAStartup(0x101, &WSAData);
 190         }
 191 #endif
 192
 193         event_base = event_base_new();
 194         evdns_base = evdns_base_new(event_base, EVDNS_BASE_DISABLE_WHEN_INACTIVE);
 195         evdns_set_log_fn(logfn);
 196
 197         if (o.servertest) {
 198                 evutil_socket_t sock;
 199                 struct sockaddr_in my_addr;
 200                 sock = socket(PF_INET, SOCK_DGRAM, 0);
 201                 if (sock == -1) {
 202                         perror("socket");
 203                         exit(1);
 204                 }
 205                 evutil_make_socket_nonblocking(sock);
 206                 my_addr.sin_family = AF_INET;
 207                 my_addr.sin_port = htons(10053);
 208                 my_addr.sin_addr.s_addr = INADDR_ANY;
 209                 if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) {
 210                         perror("bind");
 211                         exit(1);
 212                 }
 213                 evdns_add_server_port_with_base(event_base, sock, 0, evdns_server_callback, NULL);
 214         }
 215         if (optind < c) {
 216                 int res;
 217 #ifdef _WIN32
 218                 if (o.resolv_conf == NULL && !o.ns)
 219                         res = evdns_base_config_windows_nameservers(evdns_base);
 220                 else
 221 #endif
 222                 if (o.ns)
 223                         res = evdns_base_nameserver_ip_add(evdns_base, o.ns);
 224                 else
 225                         res = evdns_base_resolv_conf_parse(evdns_base,
 226                             DNS_OPTION_NAMESERVERS, o.resolv_conf);
 227
 228                 if (res < 0) {
 229                         fprintf(stderr, "Couldn't configure nameservers");
 230                         return 1;
 231                 }
 232         }
 233
 234         printf("EVUTIL_AI_CANONNAME in example = %d\n", EVUTIL_AI_CANONNAME);
 235         for (; optind < c; ++optind) {
 236                 if (o.reverse) {
 237                         struct in_addr addr;
 238                         if (evutil_inet_pton(AF_INET, v[optind], &addr)!=1) {
 239                                 fprintf(stderr, "Skipping non-IP %s\n", v[optind]);
 240                                 continue;
 241                         }
 242                         fprintf(stderr, "resolving %s...\n",v[optind]);
 243                         evdns_base_resolve_reverse(evdns_base, &addr, 0, main_callback, v[optind]);
 244                 } else if (o.use_getaddrinfo) {
 245                         struct evutil_addrinfo hints;
 246                         memset(&hints, 0, sizeof(hints));
 247                         hints.ai_family = PF_UNSPEC;
 248                         hints.ai_protocol = IPPROTO_TCP;
 249                         hints.ai_flags = EVUTIL_AI_CANONNAME;
 250                         fprintf(stderr, "resolving (fwd) %s...\n",v[optind]);
 251                         evdns_getaddrinfo(evdns_base, v[optind], NULL, &hints,
 252                             gai_callback, v[optind]);
 253                 } else {
 254                         fprintf(stderr, "resolving (fwd) %s...\n",v[optind]);
 255                         evdns_base_resolve_ipv4(evdns_base, v[optind], 0, main_callback, v[optind]);
 256                 }
 257         }
 258         fflush(stdout);
 259         event_base_dispatch(event_base);
 260         evdns_base_free(evdns_base, 1);
 261         event_base_free(event_base);
 262         return 0;
 263 }
 264