dns-example.c (6759B)
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) { 229 fprintf(stderr, "Couldn't configure nameservers\n"); 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 }