189 lines
4.9 KiB
C
189 lines
4.9 KiB
C
#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <arpa/inet.h>
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#include <stdint.h>
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#include <string.h>
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#include <poll.h>
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#include <time.h>
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#include <ctype.h>
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#include <unistd.h>
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#include <errno.h>
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#include <pthread.h>
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#include "stdio_impl.h"
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#include "syscall.h"
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#include "lookup.h"
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static void cleanup(void *p)
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{
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__syscall(SYS_close, (intptr_t)p);
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}
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static unsigned long mtime()
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{
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struct timespec ts;
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clock_gettime(CLOCK_REALTIME, &ts);
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return (unsigned long)ts.tv_sec * 1000
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+ ts.tv_nsec / 1000000;
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}
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int __res_msend_rc(int nqueries, const unsigned char *const *queries,
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const int *qlens, unsigned char *const *answers, int *alens, int asize,
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const struct resolvconf *conf)
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{
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int fd;
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int timeout, attempts, retry_interval, servfail_retry;
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union {
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struct sockaddr_in sin;
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struct sockaddr_in6 sin6;
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} sa = {0}, ns[MAXNS] = {{0}};
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socklen_t sl = sizeof sa.sin;
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int nns = 0;
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int family = AF_INET;
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int rlen;
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int next;
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int i, j;
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int cs;
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struct pollfd pfd;
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unsigned long t0, t1, t2;
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pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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timeout = 1000*conf->timeout;
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attempts = conf->attempts;
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for (nns=0; nns<conf->nns; nns++) {
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const struct address *iplit = &conf->ns[nns];
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if (iplit->family == AF_INET) {
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memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
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ns[nns].sin.sin_port = htons(53);
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ns[nns].sin.sin_family = AF_INET;
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} else {
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sl = sizeof sa.sin6;
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memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
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ns[nns].sin6.sin6_port = htons(53);
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ns[nns].sin6.sin6_scope_id = iplit->scopeid;
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ns[nns].sin6.sin6_family = family = AF_INET6;
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}
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}
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/* Get local address and open/bind a socket */
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sa.sin.sin_family = family;
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fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
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/* Handle case where system lacks IPv6 support */
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if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
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fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
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family = AF_INET;
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}
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if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
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if (fd >= 0) close(fd);
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pthread_setcancelstate(cs, 0);
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return -1;
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}
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/* Past this point, there are no errors. Each individual query will
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* yield either no reply (indicated by zero length) or an answer
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* packet which is up to the caller to interpret. */
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pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
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pthread_setcancelstate(cs, 0);
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/* Convert any IPv4 addresses in a mixed environment to v4-mapped */
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if (family == AF_INET6) {
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setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
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for (i=0; i<nns; i++) {
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if (ns[i].sin.sin_family != AF_INET) continue;
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memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
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&ns[i].sin.sin_addr, 4);
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memcpy(ns[i].sin6.sin6_addr.s6_addr,
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"\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
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ns[i].sin6.sin6_family = AF_INET6;
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ns[i].sin6.sin6_flowinfo = 0;
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ns[i].sin6.sin6_scope_id = 0;
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}
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}
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memset(alens, 0, sizeof *alens * nqueries);
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pfd.fd = fd;
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pfd.events = POLLIN;
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retry_interval = timeout / attempts;
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next = 0;
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t0 = t2 = mtime();
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t1 = t2 - retry_interval;
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for (; t2-t0 < timeout; t2=mtime()) {
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if (t2-t1 >= retry_interval) {
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/* Query all configured namservers in parallel */
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for (i=0; i<nqueries; i++)
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if (!alens[i])
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for (j=0; j<nns; j++)
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sendto(fd, queries[i],
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qlens[i], MSG_NOSIGNAL,
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(void *)&ns[j], sl);
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t1 = t2;
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servfail_retry = 2 * nqueries;
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}
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/* Wait for a response, or until time to retry */
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if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
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while ((rlen = recvfrom(fd, answers[next], asize, 0,
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(void *)&sa, (socklen_t[1]){sl})) >= 0) {
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/* Ignore non-identifiable packets */
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if (rlen < 4) continue;
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/* Ignore replies from addresses we didn't send to */
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for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
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if (j==nns) continue;
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/* Find which query this answer goes with, if any */
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for (i=next; i<nqueries && (
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answers[next][0] != queries[i][0] ||
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answers[next][1] != queries[i][1] ); i++);
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if (i==nqueries) continue;
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if (alens[i]) continue;
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/* Only accept positive or negative responses;
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* retry immediately on server failure, and ignore
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* all other codes such as refusal. */
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switch (answers[next][3] & 15) {
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case 0:
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case 3:
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break;
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case 2:
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if (servfail_retry && servfail_retry--)
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sendto(fd, queries[i],
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qlens[i], MSG_NOSIGNAL,
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(void *)&ns[j], sl);
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default:
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continue;
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}
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/* Store answer in the right slot, or update next
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* available temp slot if it's already in place. */
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alens[i] = rlen;
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if (i == next)
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for (; next<nqueries && alens[next]; next++);
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else
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memcpy(answers[i], answers[next], rlen);
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if (next == nqueries) goto out;
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}
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}
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out:
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pthread_cleanup_pop(1);
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return 0;
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}
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int __res_msend(int nqueries, const unsigned char *const *queries,
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const int *qlens, unsigned char *const *answers, int *alens, int asize)
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{
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struct resolvconf conf;
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if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
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return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
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}
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