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