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 *
debug_ntoa(u32 address)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
main_callback(int result,char type,int count,int ttl,void * addrs,void * orig)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
gai_callback(int err,struct evutil_addrinfo * ai,void * arg)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
evdns_server_callback(struct evdns_server_request * req,void * data)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
logfn(int is_warn,const char * msg)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
main(int c,char ** v)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