1 /* $NetBSD: dns-example.c,v 1.1.1.1 2013/04/11 16:43:31 christos Exp $ */ 2 /* 3 This example code shows how to use the high-level, low-level, and 4 server-level interfaces of evdns. 5 6 XXX It's pretty ugly and should probably be cleaned up. 7 */ 8 9 #include <event2/event-config.h> 10 11 /* Compatibility for possible missing IPv6 declarations */ 12 #include "../ipv6-internal.h" 13 14 #include <sys/types.h> 15 16 #ifdef WIN32 17 #include <winsock2.h> 18 #include <ws2tcpip.h> 19 #else 20 #include <sys/socket.h> 21 #include <netinet/in.h> 22 #include <arpa/inet.h> 23 #endif 24 25 #include <event2/event.h> 26 #include <event2/dns.h> 27 #include <event2/dns_struct.h> 28 #include <event2/util.h> 29 30 #ifdef _EVENT_HAVE_NETINET_IN6_H 31 #include <netinet/in6.h> 32 #endif 33 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 38 #define u32 ev_uint32_t 39 #define u8 ev_uint8_t 40 41 static const char * 42 debug_ntoa(u32 address) 43 { 44 static char buf[32]; 45 u32 a = ntohl(address); 46 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d", 47 (int)(u8)((a>>24)&0xff), 48 (int)(u8)((a>>16)&0xff), 49 (int)(u8)((a>>8 )&0xff), 50 (int)(u8)((a )&0xff)); 51 return buf; 52 } 53 54 static void 55 main_callback(int result, char type, int count, int ttl, 56 void *addrs, void *orig) { 57 char *n = (char*)orig; 58 int i; 59 for (i = 0; i < count; ++i) { 60 if (type == DNS_IPv4_A) { 61 printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i])); 62 } else if (type == DNS_PTR) { 63 printf("%s: %s\n", n, ((char**)addrs)[i]); 64 } 65 } 66 if (!count) { 67 printf("%s: No answer (%d)\n", n, result); 68 } 69 fflush(stdout); 70 } 71 72 static void 73 gai_callback(int err, struct evutil_addrinfo *ai, void *arg) 74 { 75 const char *name = arg; 76 int i; 77 if (err) { 78 printf("%s: %s\n", name, evutil_gai_strerror(err)); 79 } 80 if (ai && ai->ai_canonname) 81 printf(" %s ==> %s\n", name, ai->ai_canonname); 82 for (i=0; ai; ai = ai->ai_next, ++i) { 83 char buf[128]; 84 if (ai->ai_family == PF_INET) { 85 struct sockaddr_in *sin = 86 (struct sockaddr_in*)ai->ai_addr; 87 evutil_inet_ntop(AF_INET, &sin->sin_addr, buf, 88 sizeof(buf)); 89 printf("[%d] %s: %s\n",i,name,buf); 90 } else { 91 struct sockaddr_in6 *sin6 = 92 (struct sockaddr_in6*)ai->ai_addr; 93 evutil_inet_ntop(AF_INET6, &sin6->sin6_addr, buf, 94 sizeof(buf)); 95 printf("[%d] %s: %s\n",i,name,buf); 96 } 97 } 98 } 99 100 static void 101 evdns_server_callback(struct evdns_server_request *req, void *data) 102 { 103 int i, r; 104 (void)data; 105 /* dummy; give 192.168.11.11 as an answer for all A questions, 106 * give foo.bar.example.com as an answer for all PTR questions. */ 107 for (i = 0; i < req->nquestions; ++i) { 108 u32 ans = htonl(0xc0a80b0bUL); 109 if (req->questions[i]->type == EVDNS_TYPE_A && 110 req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { 111 printf(" -- replying for %s (A)\n", req->questions[i]->name); 112 r = evdns_server_request_add_a_reply(req, req->questions[i]->name, 113 1, &ans, 10); 114 if (r<0) 115 printf("eeep, didn't work.\n"); 116 } else if (req->questions[i]->type == EVDNS_TYPE_PTR && 117 req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { 118 printf(" -- replying for %s (PTR)\n", req->questions[i]->name); 119 r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name, 120 "foo.bar.example.com", 10); 121 if (r<0) 122 printf("ugh, no luck"); 123 } else { 124 printf(" -- skipping %s [%d %d]\n", req->questions[i]->name, 125 req->questions[i]->type, req->questions[i]->dns_question_class); 126 } 127 } 128 129 r = evdns_server_request_respond(req, 0); 130 if (r<0) 131 printf("eeek, couldn't send reply.\n"); 132 } 133 134 static int verbose = 0; 135 136 static void 137 logfn(int is_warn, const char *msg) { 138 if (!is_warn && !verbose) 139 return; 140 fprintf(stderr, "%s: %s\n", is_warn?"WARN":"INFO", msg); 141 } 142 143 int 144 main(int c, char **v) { 145 int idx; 146 int reverse = 0, servertest = 0, use_getaddrinfo = 0; 147 struct event_base *event_base = NULL; 148 struct evdns_base *evdns_base = NULL; 149 const char *resolv_conf = NULL; 150 if (c<2) { 151 fprintf(stderr, "syntax: %s [-x] [-v] [-c resolv.conf] hostname\n", v[0]); 152 fprintf(stderr, "syntax: %s [-servertest]\n", v[0]); 153 return 1; 154 } 155 idx = 1; 156 while (idx < c && v[idx][0] == '-') { 157 if (!strcmp(v[idx], "-x")) 158 reverse = 1; 159 else if (!strcmp(v[idx], "-v")) 160 verbose = 1; 161 else if (!strcmp(v[idx], "-g")) 162 use_getaddrinfo = 1; 163 else if (!strcmp(v[idx], "-servertest")) 164 servertest = 1; 165 else if (!strcmp(v[idx], "-c")) { 166 if (idx + 1 < c) 167 resolv_conf = v[++idx]; 168 else 169 fprintf(stderr, "-c needs an argument\n"); 170 } else 171 fprintf(stderr, "Unknown option %s\n", v[idx]); 172 ++idx; 173 } 174 175 #ifdef WIN32 176 { 177 WSADATA WSAData; 178 WSAStartup(0x101, &WSAData); 179 } 180 #endif 181 182 event_base = event_base_new(); 183 evdns_base = evdns_base_new(event_base, 0); 184 evdns_set_log_fn(logfn); 185 186 if (servertest) { 187 evutil_socket_t sock; 188 struct sockaddr_in my_addr; 189 sock = socket(PF_INET, SOCK_DGRAM, 0); 190 if (sock == -1) { 191 perror("socket"); 192 exit(1); 193 } 194 evutil_make_socket_nonblocking(sock); 195 my_addr.sin_family = AF_INET; 196 my_addr.sin_port = htons(10053); 197 my_addr.sin_addr.s_addr = INADDR_ANY; 198 if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) { 199 perror("bind"); 200 exit(1); 201 } 202 evdns_add_server_port_with_base(event_base, sock, 0, evdns_server_callback, NULL); 203 } 204 if (idx < c) { 205 int res; 206 #ifdef WIN32 207 if (resolv_conf == NULL) 208 res = evdns_base_config_windows_nameservers(evdns_base); 209 else 210 #endif 211 res = evdns_base_resolv_conf_parse(evdns_base, 212 DNS_OPTION_NAMESERVERS, 213 resolv_conf ? resolv_conf : "/etc/resolv.conf"); 214 215 if (res < 0) { 216 fprintf(stderr, "Couldn't configure nameservers"); 217 return 1; 218 } 219 } 220 221 printf("EVUTIL_AI_CANONNAME in example = %d\n", EVUTIL_AI_CANONNAME); 222 for (; idx < c; ++idx) { 223 if (reverse) { 224 struct in_addr addr; 225 if (evutil_inet_pton(AF_INET, v[idx], &addr)!=1) { 226 fprintf(stderr, "Skipping non-IP %s\n", v[idx]); 227 continue; 228 } 229 fprintf(stderr, "resolving %s...\n",v[idx]); 230 evdns_base_resolve_reverse(evdns_base, &addr, 0, main_callback, v[idx]); 231 } else if (use_getaddrinfo) { 232 struct evutil_addrinfo hints; 233 memset(&hints, 0, sizeof(hints)); 234 hints.ai_family = PF_UNSPEC; 235 hints.ai_protocol = IPPROTO_TCP; 236 hints.ai_flags = EVUTIL_AI_CANONNAME; 237 fprintf(stderr, "resolving (fwd) %s...\n",v[idx]); 238 evdns_getaddrinfo(evdns_base, v[idx], NULL, &hints, 239 gai_callback, v[idx]); 240 } else { 241 fprintf(stderr, "resolving (fwd) %s...\n",v[idx]); 242 evdns_base_resolve_ipv4(evdns_base, v[idx], 0, main_callback, v[idx]); 243 } 244 } 245 fflush(stdout); 246 event_base_dispatch(event_base); 247 return 0; 248 } 249 250