1 #include <sys/socket.h>
2 #include <netinet/in.h>
13 #include "stdio_impl.h"
17 static void cleanup(void *p)
19 __syscall(SYS_close, (intptr_t)p);
22 static unsigned long mtime()
25 clock_gettime(CLOCK_REALTIME, &ts);
26 return (unsigned long)ts.tv_sec * 1000
27 + ts.tv_nsec / 1000000;
30 int __res_msend(int nqueries, const unsigned char *const *queries,
31 const int *qlens, unsigned char *const *answers, int *alens, int asize)
35 unsigned char _buf[256];
36 char line[64], *s, *z;
37 int timeout = 5000, attempts = 2, retry_interval, servfail_retry;
39 struct sockaddr_in sin;
40 struct sockaddr_in6 sin6;
41 } sa = {0}, ns[3] = {{0}};
42 socklen_t sl = sizeof sa.sin;
50 unsigned long t0, t1, t2;
53 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
55 /* Get nameservers from resolv.conf, fallback to localhost */
56 f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
57 if (!f) switch (errno) {
65 for (nns=0; nns<3 && fgets(line, sizeof line, f); ) {
66 if (!strncmp(line, "options", 7) && isspace(line[7])) {
69 p = strstr(line, "timeout:");
70 if (p && isdigit(p[8])) {
72 x = strtoul(p, &z, 10);
73 if (z != p) timeout = x < 30 ? x*1000 : 30000;
75 p = strstr(line, "attempts:");
76 if (p && isdigit(p[9])) {
78 x = strtoul(p, &z, 10);
79 if (z != p) attempts = x < 10 ? x : 10;
80 if (!attempts) attempts = 1;
83 if (strncmp(line, "nameserver", 10) || !isspace(line[10]))
85 for (s=line+11; isspace(*s); s++);
86 for (z=s; *z && !isspace(*z); z++);
89 if (__lookup_ipliteral(&iplit, s, AF_UNSPEC)>0) {
90 if (iplit.family == AF_INET) {
91 memcpy(&ns[nns].sin.sin_addr, iplit.addr, 4);
92 ns[nns].sin.sin_port = htons(53);
93 ns[nns++].sin.sin_family = AF_INET;
96 memcpy(&ns[nns].sin6.sin6_addr, iplit.addr, 16);
97 ns[nns].sin6.sin6_port = htons(53);
98 ns[nns].sin6.sin6_scope_id = iplit.scopeid;
99 ns[nns++].sin6.sin6_family = family = AF_INET6;
106 ns[0].sin.sin_family = AF_INET;
107 ns[0].sin.sin_port = htons(53);
108 ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
112 /* Get local address and open/bind a socket */
113 sa.sin.sin_family = family;
114 fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
116 /* Handle case where system lacks IPv6 support */
117 if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
118 fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
121 if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1;
123 /* Past this point, there are no errors. Each individual query will
124 * yield either no reply (indicated by zero length) or an answer
125 * packet which is up to the caller to interpret. */
127 pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
128 pthread_setcancelstate(cs, 0);
130 /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
131 if (family == AF_INET6) {
132 setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
133 for (i=0; i<nns; i++) {
134 if (ns[i].sin.sin_family != AF_INET) continue;
135 memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
136 &ns[i].sin.sin_addr, 4);
137 memcpy(ns[i].sin6.sin6_addr.s6_addr,
138 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
139 ns[i].sin6.sin6_family = AF_INET6;
140 ns[i].sin6.sin6_flowinfo = 0;
141 ns[i].sin6.sin6_scope_id = 0;
145 memset(alens, 0, sizeof *alens * nqueries);
149 retry_interval = timeout / attempts;
152 t1 = t2 - retry_interval;
154 for (; t2-t0 < timeout; t2=mtime()) {
155 if (t2-t1 >= retry_interval) {
156 /* Query all configured namservers in parallel */
157 for (i=0; i<nqueries; i++)
159 for (j=0; j<nns; j++)
160 sendto(fd, queries[i],
161 qlens[i], MSG_NOSIGNAL,
164 servfail_retry = 2 * nqueries;
167 /* Wait for a response, or until time to retry */
168 if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
170 while ((rlen = recvfrom(fd, answers[next], asize, 0,
171 (void *)&sa, (socklen_t[1]){sl})) >= 0) {
173 /* Ignore non-identifiable packets */
174 if (rlen < 4) continue;
176 /* Ignore replies from addresses we didn't send to */
177 for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
178 if (j==nns) continue;
180 /* Find which query this answer goes with, if any */
181 for (i=next; i<nqueries && (
182 answers[next][0] != queries[i][0] ||
183 answers[next][1] != queries[i][1] ); i++);
184 if (i==nqueries) continue;
185 if (alens[i]) continue;
187 /* Only accept positive or negative responses;
188 * retry immediately on server failure, and ignore
189 * all other codes such as refusal. */
190 switch (answers[next][3] & 15) {
195 if (servfail_retry && servfail_retry--)
196 sendto(fd, queries[i],
197 qlens[i], MSG_NOSIGNAL,
203 /* Store answer in the right slot, or update next
204 * available temp slot if it's already in place. */
207 for (; next<nqueries && alens[next]; next++);
209 memcpy(answers[i], answers[next], rlen);
211 if (next == nqueries) goto out;
215 pthread_cleanup_pop(1);