nsz Git - musl/blob - 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         struct pollfd *pfd = p;
  20         for (int i=0; pfd[i].fd >= -1; i++)
  21                 if (pfd[i].fd >= 0) __syscall(SYS_close, pfd[i].fd);
  22 }
  23
  24 static unsigned long mtime()
  25 {
  26         struct timespec ts;
  27         clock_gettime(CLOCK_REALTIME, &ts);
  28         return (unsigned long)ts.tv_sec * 1000
  29                 + ts.tv_nsec / 1000000;
  30 }
  31
  32 int __res_msend_rc(int nqueries, const unsigned char *const *queries,
  33         const int *qlens, unsigned char *const *answers, int *alens, int asize,
  34         const struct resolvconf *conf)
  35 {
  36         int fd;
  37         int timeout, attempts, retry_interval, servfail_retry;
  38         union {
  39                 struct sockaddr_in sin;
  40                 struct sockaddr_in6 sin6;
  41         } sa = {0}, ns[MAXNS] = {{0}};
  42         socklen_t sl = sizeof sa.sin;
  43         int nns = 0;
  44         int family = AF_INET;
  45         int rlen;
  46         int next;
  47         int i, j;
  48         int cs;
  49         struct pollfd pfd[nqueries+2];
  50         unsigned long t0, t1, t2;
  51
  52         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
  53
  54         timeout = 1000*conf->timeout;
  55         attempts = conf->attempts;
  56
  57         for (nns=0; nns<conf->nns; nns++) {
  58                 const struct address *iplit = &conf->ns[nns];
  59                 if (iplit->family == AF_INET) {
  60                         memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
  61                         ns[nns].sin.sin_port = htons(53);
  62                         ns[nns].sin.sin_family = AF_INET;
  63                 } else {
  64                         sl = sizeof sa.sin6;
  65                         memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
  66                         ns[nns].sin6.sin6_port = htons(53);
  67                         ns[nns].sin6.sin6_scope_id = iplit->scopeid;
  68                         ns[nns].sin6.sin6_family = family = AF_INET6;
  69                 }
  70         }
  71
  72         /* Get local address and open/bind a socket */
  73         fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
  74
  75         /* Handle case where system lacks IPv6 support */
  76         if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
  77                 for (i=0; i<nns && conf->ns[nns].family == AF_INET6; i++);
  78                 if (i==nns) {
  79                         pthread_setcancelstate(cs, 0);
  80                         return -1;
  81                 }
  82                 fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
  83                 family = AF_INET;
  84                 sl = sizeof sa.sin;
  85         }
  86         sa.sin.sin_family = family;
  87         if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
  88                 if (fd >= 0) close(fd);
  89                 pthread_setcancelstate(cs, 0);
  90                 return -1;
  91         }
  92
  93         /* Past this point, there are no errors. Each individual query will
  94          * yield either no reply (indicated by zero length) or an answer
  95          * packet which is up to the caller to interpret. */
  96
  97         for (i=0; i<nqueries; i++) pfd[i].fd = -1;
  98         pfd[nqueries].fd = fd;
  99         pfd[nqueries].events = POLLIN;
 100         pfd[nqueries+1].fd = -2;
 101
 102         pthread_cleanup_push(cleanup, pfd);
 103         pthread_setcancelstate(cs, 0);
 104
 105         /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
 106         if (family == AF_INET6) {
 107                 setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
 108                 for (i=0; i<nns; i++) {
 109                         if (ns[i].sin.sin_family != AF_INET) continue;
 110                         memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
 111                                 &ns[i].sin.sin_addr, 4);
 112                         memcpy(ns[i].sin6.sin6_addr.s6_addr,
 113                                 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
 114                         ns[i].sin6.sin6_family = AF_INET6;
 115                         ns[i].sin6.sin6_flowinfo = 0;
 116                         ns[i].sin6.sin6_scope_id = 0;
 117                 }
 118         }
 119
 120         memset(alens, 0, sizeof *alens * nqueries);
 121
 122         retry_interval = timeout / attempts;
 123         next = 0;
 124         t0 = t2 = mtime();
 125         t1 = t2 - retry_interval;
 126
 127         for (; t2-t0 < timeout; t2=mtime()) {
 128                 if (t2-t1 >= retry_interval) {
 129                         /* Query all configured namservers in parallel */
 130                         for (i=0; i<nqueries; i++)
 131                                 if (!alens[i])
 132                                         for (j=0; j<nns; j++)
 133                                                 sendto(fd, queries[i],
 134                                                         qlens[i], MSG_NOSIGNAL,
 135                                                         (void *)&ns[j], sl);
 136                         t1 = t2;
 137                         servfail_retry = 2 * nqueries;
 138                 }
 139
 140                 /* Wait for a response, or until time to retry */
 141                 if (poll(pfd, nqueries+1, t1+retry_interval-t2) <= 0) continue;
 142
 143                 while ((rlen = recvfrom(fd, answers[next], asize, 0,
 144                   (void *)&sa, (socklen_t[1]){sl})) >= 0) {
 145
 146                         /* Ignore non-identifiable packets */
 147                         if (rlen < 4) continue;
 148
 149                         /* Ignore replies from addresses we didn't send to */
 150                         for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
 151                         if (j==nns) continue;
 152
 153                         /* Find which query this answer goes with, if any */
 154                         for (i=next; i<nqueries && (
 155                                 answers[next][0] != queries[i][0] ||
 156                                 answers[next][1] != queries[i][1] ); i++);
 157                         if (i==nqueries) continue;
 158                         if (alens[i]) continue;
 159
 160                         /* Only accept positive or negative responses;
 161                          * retry immediately on server failure, and ignore
 162                          * all other codes such as refusal. */
 163                         switch (answers[next][3] & 15) {
 164                         case 0:
 165                         case 3:
 166                                 break;
 167                         case 2:
 168                                 if (servfail_retry && servfail_retry--)
 169                                         sendto(fd, queries[i],
 170                                                 qlens[i], MSG_NOSIGNAL,
 171                                                 (void *)&ns[j], sl);
 172                         default:
 173                                 continue;
 174                         }
 175
 176                         /* Store answer in the right slot, or update next
 177                          * available temp slot if it's already in place. */
 178                         alens[i] = rlen;
 179                         if (i == next)
 180                                 for (; next<nqueries && alens[next]; next++);
 181                         else
 182                                 memcpy(answers[i], answers[next], rlen);
 183
 184                         if (next == nqueries) goto out;
 185                 }
 186         }
 187 out:
 188         pthread_cleanup_pop(1);
 189
 190         return 0;
 191 }
 192
 193 int __res_msend(int nqueries, const unsigned char *const *queries,
 194         const int *qlens, unsigned char *const *answers, int *alens, int asize)
 195 {
 196         struct resolvconf conf;
 197         if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
 198         return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
 199 }