res_msend.c raw
1 #include <sys/socket.h>
2 #include <netinet/in.h>
3 #include <netdb.h>
4 #include <arpa/inet.h>
5 #include <stdint.h>
6 #include <string.h>
7 #include <poll.h>
8 #include <time.h>
9 #include <ctype.h>
10 #include <unistd.h>
11 #include <errno.h>
12 #include <pthread.h>
13 #include "stdio_impl.h"
14 #include "syscall.h"
15 #include "lookup.h"
16
17 static void cleanup(void *p)
18 {
19 __syscall(SYS_close, (intptr_t)p);
20 }
21
22 static unsigned long mtime()
23 {
24 struct timespec ts;
25 clock_gettime(CLOCK_REALTIME, &ts);
26 return (unsigned long)ts.tv_sec * 1000
27 + ts.tv_nsec / 1000000;
28 }
29
30 int __res_msend_rc(int nqueries, const unsigned char *const *queries,
31 const int *qlens, unsigned char *const *answers, int *alens, int asize,
32 const struct resolvconf *conf)
33 {
34 int fd;
35 int timeout, attempts, retry_interval, servfail_retry;
36 union {
37 struct sockaddr_in sin;
38 struct sockaddr_in6 sin6;
39 } sa = {0}, ns[MAXNS] = {{0}};
40 socklen_t sl = sizeof sa.sin;
41 int nns = 0;
42 int family = AF_INET;
43 int rlen;
44 int next;
45 int i, j;
46 int cs;
47 struct pollfd pfd;
48 unsigned long t0, t1, t2;
49
50 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
51
52 timeout = 1000*conf->timeout;
53 attempts = conf->attempts;
54
55 for (nns=0; nns<conf->nns; nns++) {
56 const struct address *iplit = &conf->ns[nns];
57 if (iplit->family == AF_INET) {
58 memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
59 ns[nns].sin.sin_port = htons(53);
60 ns[nns].sin.sin_family = AF_INET;
61 } else {
62 sl = sizeof sa.sin6;
63 memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
64 ns[nns].sin6.sin6_port = htons(53);
65 ns[nns].sin6.sin6_scope_id = iplit->scopeid;
66 ns[nns].sin6.sin6_family = family = AF_INET6;
67 }
68 }
69
70 /* Get local address and open/bind a socket */
71 sa.sin.sin_family = family;
72 fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
73
74 /* Handle case where system lacks IPv6 support */
75 if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
76 fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
77 family = AF_INET;
78 }
79 if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
80 if (fd >= 0) close(fd);
81 pthread_setcancelstate(cs, 0);
82 return -1;
83 }
84
85 /* Past this point, there are no errors. Each individual query will
86 * yield either no reply (indicated by zero length) or an answer
87 * packet which is up to the caller to interpret. */
88
89 pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
90 pthread_setcancelstate(cs, 0);
91
92 /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
93 if (family == AF_INET6) {
94 setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
95 for (i=0; i<nns; i++) {
96 if (ns[i].sin.sin_family != AF_INET) continue;
97 memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
98 &ns[i].sin.sin_addr, 4);
99 memcpy(ns[i].sin6.sin6_addr.s6_addr,
100 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
101 ns[i].sin6.sin6_family = AF_INET6;
102 ns[i].sin6.sin6_flowinfo = 0;
103 ns[i].sin6.sin6_scope_id = 0;
104 }
105 }
106
107 memset(alens, 0, sizeof *alens * nqueries);
108
109 pfd.fd = fd;
110 pfd.events = POLLIN;
111 retry_interval = timeout / attempts;
112 next = 0;
113 t0 = t2 = mtime();
114 t1 = t2 - retry_interval;
115
116 for (; t2-t0 < timeout; t2=mtime()) {
117 if (t2-t1 >= retry_interval) {
118 /* Query all configured namservers in parallel */
119 for (i=0; i<nqueries; i++)
120 if (!alens[i])
121 for (j=0; j<nns; j++)
122 sendto(fd, queries[i],
123 qlens[i], MSG_NOSIGNAL,
124 (void *)&ns[j], sl);
125 t1 = t2;
126 servfail_retry = 2 * nqueries;
127 }
128
129 /* Wait for a response, or until time to retry */
130 if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
131
132 while ((rlen = recvfrom(fd, answers[next], asize, 0,
133 (void *)&sa, (socklen_t[1]){sl})) >= 0) {
134
135 /* Ignore non-identifiable packets */
136 if (rlen < 4) continue;
137
138 /* Ignore replies from addresses we didn't send to */
139 for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
140 if (j==nns) continue;
141
142 /* Find which query this answer goes with, if any */
143 for (i=next; i<nqueries && (
144 answers[next][0] != queries[i][0] ||
145 answers[next][1] != queries[i][1] ); i++);
146 if (i==nqueries) continue;
147 if (alens[i]) continue;
148
149 /* Only accept positive or negative responses;
150 * retry immediately on server failure, and ignore
151 * all other codes such as refusal. */
152 switch (answers[next][3] & 15) {
153 case 0:
154 case 3:
155 break;
156 case 2:
157 if (servfail_retry && servfail_retry--)
158 sendto(fd, queries[i],
159 qlens[i], MSG_NOSIGNAL,
160 (void *)&ns[j], sl);
161 default:
162 continue;
163 }
164
165 /* Store answer in the right slot, or update next
166 * available temp slot if it's already in place. */
167 alens[i] = rlen;
168 if (i == next)
169 for (; next<nqueries && alens[next]; next++);
170 else
171 memcpy(answers[i], answers[next], rlen);
172
173 if (next == nqueries) goto out;
174 }
175 }
176 out:
177 pthread_cleanup_pop(1);
178
179 return 0;
180 }
181
182 int __res_msend(int nqueries, const unsigned char *const *queries,
183 const int *qlens, unsigned char *const *answers, int *alens, int asize)
184 {
185 struct resolvconf conf;
186 if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
187 return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
188 }
189