src/network/res_msend.c

   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 }