dns-example.c revision 1.1.1.3
1 /* $NetBSD: dns-example.c,v 1.1.1.3 2021/04/07 02:43:15 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 EVENT__HAVE_UNISTD_H 17 #include <unistd.h> 18 #endif 19 20 #ifdef _WIN32 21 #include <winsock2.h> 22 #include <ws2tcpip.h> 23 #include <getopt.h> 24 #else 25 #include <sys/socket.h> 26 #include <netinet/in.h> 27 #include <arpa/inet.h> 28 #endif 29 30 #include <event2/event.h> 31 #include <event2/dns.h> 32 #include <event2/dns_struct.h> 33 #include <event2/util.h> 34 35 #ifdef EVENT__HAVE_NETINET_IN6_H 36 #include <netinet/in6.h> 37 #endif 38 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 43 #define u32 ev_uint32_t 44 #define u8 ev_uint8_t 45 46 static const char * 47 debug_ntoa(u32 address) 48 { 49 static char buf[32]; 50 u32 a = ntohl(address); 51 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d", 52 (int)(u8)((a>>24)&0xff), 53 (int)(u8)((a>>16)&0xff), 54 (int)(u8)((a>>8 )&0xff), 55 (int)(u8)((a )&0xff)); 56 return buf; 57 } 58 59 static void 60 main_callback(int result, char type, int count, int ttl, 61 void *addrs, void *orig) { 62 char *n = (char*)orig; 63 int i; 64 for (i = 0; i < count; ++i) { 65 if (type == DNS_IPv4_A) { 66 printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i])); 67 } else if (type == DNS_PTR) { 68 printf("%s: %s\n", n, ((char**)addrs)[i]); 69 } 70 } 71 if (!count) { 72 printf("%s: No answer (%d)\n", n, result); 73 } 74 fflush(stdout); 75 } 76 77 static void 78 gai_callback(int err, struct evutil_addrinfo *ai, void *arg) 79 { 80 const char *name = arg; 81 int i; 82 struct evutil_addrinfo *first_ai = ai; 83 84 if (err) { 85 printf("%s: %s\n", name, evutil_gai_strerror(err)); 86 } 87 if (ai && ai->ai_canonname) 88 printf(" %s ==> %s\n", name, ai->ai_canonname); 89 for (i=0; ai; ai = ai->ai_next, ++i) { 90 char buf[128]; 91 if (ai->ai_family == PF_INET) { 92 struct sockaddr_in *sin = 93 (struct sockaddr_in*)ai->ai_addr; 94 evutil_inet_ntop(AF_INET, &sin->sin_addr, buf, 95 sizeof(buf)); 96 printf("[%d] %s: %s\n",i,name,buf); 97 } else { 98 struct sockaddr_in6 *sin6 = 99 (struct sockaddr_in6*)ai->ai_addr; 100 evutil_inet_ntop(AF_INET6, &sin6->sin6_addr, buf, 101 sizeof(buf)); 102 printf("[%d] %s: %s\n",i,name,buf); 103 } 104 } 105 106 if (first_ai) 107 evutil_freeaddrinfo(first_ai); 108 } 109 110 static void 111 evdns_server_callback(struct evdns_server_request *req, void *data) 112 { 113 int i, r; 114 (void)data; 115 /* dummy; give 192.168.11.11 as an answer for all A questions, 116 * give foo.bar.example.com as an answer for all PTR questions. */ 117 for (i = 0; i < req->nquestions; ++i) { 118 u32 ans = htonl(0xc0a80b0bUL); 119 if (req->questions[i]->type == EVDNS_TYPE_A && 120 req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { 121 printf(" -- replying for %s (A)\n", req->questions[i]->name); 122 r = evdns_server_request_add_a_reply(req, req->questions[i]->name, 123 1, &ans, 10); 124 if (r<0) 125 printf("eeep, didn't work.\n"); 126 } else if (req->questions[i]->type == EVDNS_TYPE_PTR && 127 req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { 128 printf(" -- replying for %s (PTR)\n", req->questions[i]->name); 129 r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name, 130 "foo.bar.example.com", 10); 131 if (r<0) 132 printf("ugh, no luck"); 133 } else { 134 printf(" -- skipping %s [%d %d]\n", req->questions[i]->name, 135 req->questions[i]->type, req->questions[i]->dns_question_class); 136 } 137 } 138 139 r = evdns_server_request_respond(req, 0); 140 if (r<0) 141 printf("eeek, couldn't send reply.\n"); 142 } 143 144 static int verbose = 0; 145 146 static void 147 logfn(int is_warn, const char *msg) { 148 if (!is_warn && !verbose) 149 return; 150 fprintf(stderr, "%s: %s\n", is_warn?"WARN":"INFO", msg); 151 } 152 153 int 154 main(int c, char **v) { 155 struct options { 156 int reverse; 157 int use_getaddrinfo; 158 int servertest; 159 const char *resolv_conf; 160 const char *ns; 161 }; 162 struct options o; 163 int opt; 164 struct event_base *event_base = NULL; 165 struct evdns_base *evdns_base = NULL; 166 167 memset(&o, 0, sizeof(o)); 168 169 if (c < 2) { 170 fprintf(stderr, "syntax: %s [-x] [-v] [-c resolv.conf] [-s ns] hostname\n", v[0]); 171 fprintf(stderr, "syntax: %s [-T]\n", v[0]); 172 return 1; 173 } 174 175 while ((opt = getopt(c, v, "xvc:Ts:g")) != -1) { 176 switch (opt) { 177 case 'x': o.reverse = 1; break; 178 case 'v': ++verbose; break; 179 case 'g': o.use_getaddrinfo = 1; break; 180 case 'T': o.servertest = 1; break; 181 case 'c': o.resolv_conf = optarg; break; 182 case 's': o.ns = optarg; break; 183 default : fprintf(stderr, "Unknown option %c\n", opt); break; 184 } 185 } 186 187 #ifdef _WIN32 188 { 189 WSADATA WSAData; 190 WSAStartup(0x101, &WSAData); 191 } 192 #endif 193 194 event_base = event_base_new(); 195 evdns_base = evdns_base_new(event_base, EVDNS_BASE_DISABLE_WHEN_INACTIVE); 196 evdns_set_log_fn(logfn); 197 198 if (o.servertest) { 199 evutil_socket_t sock; 200 struct sockaddr_in my_addr; 201 sock = socket(PF_INET, SOCK_DGRAM, 0); 202 if (sock == -1) { 203 perror("socket"); 204 exit(1); 205 } 206 evutil_make_socket_nonblocking(sock); 207 my_addr.sin_family = AF_INET; 208 my_addr.sin_port = htons(10053); 209 my_addr.sin_addr.s_addr = INADDR_ANY; 210 if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) { 211 perror("bind"); 212 exit(1); 213 } 214 evdns_add_server_port_with_base(event_base, sock, 0, evdns_server_callback, NULL); 215 } 216 if (optind < c) { 217 int res; 218 #ifdef _WIN32 219 if (o.resolv_conf == NULL && !o.ns) 220 res = evdns_base_config_windows_nameservers(evdns_base); 221 else 222 #endif 223 if (o.ns) 224 res = evdns_base_nameserver_ip_add(evdns_base, o.ns); 225 else 226 res = evdns_base_resolv_conf_parse(evdns_base, 227 DNS_OPTION_NAMESERVERS, o.resolv_conf); 228 229 if (res) { 230 fprintf(stderr, "Couldn't configure nameservers\n"); 231 return 1; 232 } 233 } 234 235 printf("EVUTIL_AI_CANONNAME in example = %d\n", EVUTIL_AI_CANONNAME); 236 for (; optind < c; ++optind) { 237 if (o.reverse) { 238 struct in_addr addr; 239 if (evutil_inet_pton(AF_INET, v[optind], &addr)!=1) { 240 fprintf(stderr, "Skipping non-IP %s\n", v[optind]); 241 continue; 242 } 243 fprintf(stderr, "resolving %s...\n",v[optind]); 244 evdns_base_resolve_reverse(evdns_base, &addr, 0, main_callback, v[optind]); 245 } else if (o.use_getaddrinfo) { 246 struct evutil_addrinfo hints; 247 memset(&hints, 0, sizeof(hints)); 248 hints.ai_family = PF_UNSPEC; 249 hints.ai_protocol = IPPROTO_TCP; 250 hints.ai_flags = EVUTIL_AI_CANONNAME; 251 fprintf(stderr, "resolving (fwd) %s...\n",v[optind]); 252 evdns_getaddrinfo(evdns_base, v[optind], NULL, &hints, 253 gai_callback, v[optind]); 254 } else { 255 fprintf(stderr, "resolving (fwd) %s...\n",v[optind]); 256 evdns_base_resolve_ipv4(evdns_base, v[optind], 0, main_callback, v[optind]); 257 } 258 } 259 fflush(stdout); 260 event_base_dispatch(event_base); 261 evdns_base_free(evdns_base, 1); 262 event_base_free(event_base); 263 return 0; 264 } 265 266
Indexes created Wed Mar 04 15:26:31 UTC 2026