#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(int nqueries, const unsigned char *const *queries, const int *qlens, unsigned char *const *answers, int *alens, int asize) { int fd; FILE *f, _f; unsigned char _buf[256]; char line[64], *s, *z; int timeout = 5000, attempts = 2, retry_interval, servfail_retry; union { struct sockaddr_in sin; struct sockaddr_in6 sin6; } sa = {0}, ns[3] = {{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; struct address iplit; pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs); /* Get nameservers from resolv.conf, fallback to localhost */ f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf); if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) { if (!strncmp(line, "options", 7) && isspace(line[7])) { unsigned long x; char *p, *z; p = strstr(line, "timeout:"); if (p && isdigit(p[8])) { p += 8; x = strtoul(p, &z, 10); if (z != p) timeout = x < 30 ? x*1000 : 30000; } p = strstr(line, "attempts:"); if (p && isdigit(p[9])) { p += 9; x = strtoul(p, &z, 10); if (z != p) attempts = x < 10 ? x : 10; if (!attempts) attempts = 1; } } if (strncmp(line, "nameserver", 10) || !isspace(line[10])) continue; for (s=line+11; isspace(*s); s++); for (z=s; *z && !isspace(*z); z++); *z=0; if (__lookup_ipliteral(&iplit, s, AF_UNSPEC)>0) { 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; } } } if (f) __fclose_ca(f); if (!nns) { ns[0].sin.sin_family = AF_INET; ns[0].sin.sin_port = htons(53); ns[0].sin.sin_addr.s_addr = htonl(0x7f000001); nns=1; } /* 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) 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; }