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https://github.com/jart/cosmopolitan.git
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43fe5956ad
Now that our socket system call polyfills are good enough to support Musl's DNS library we should be using that rather than the barebones domain name system implementation we rolled on our own. There's many benefits to making this change. So many, that I myself wouldn't feel qualified to enumerate them all. The Musl DNS code had to be changed in order to support Windows of course, which looks very solid so far
367 lines
13 KiB
C
367 lines
13 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8 :vi │
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╚──────────────────────────────────────────────────────────────────────────────╝
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│ │
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│ Musl Libc │
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│ Copyright © 2005-2014 Rich Felker, et al. │
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│ │
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│ Permission is hereby granted, free of charge, to any person obtaining │
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│ a copy of this software and associated documentation files (the │
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│ "Software"), to deal in the Software without restriction, including │
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│ without limitation the rights to use, copy, modify, merge, publish, │
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│ distribute, sublicense, and/or sell copies of the Software, and to │
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│ permit persons to whom the Software is furnished to do so, subject to │
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│ the following conditions: │
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│ │
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│ The above copyright notice and this permission notice shall be │
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│ included in all copies or substantial portions of the Software. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
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│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
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│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
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│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
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│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
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│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
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│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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│ │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/calls/struct/timespec.h"
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#include "libc/calls/weirdtypes.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/sock/sock.h"
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#include "libc/sock/sock.h"
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#include "libc/sock/struct/msghdr.h"
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#include "libc/sock/struct/pollfd.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/af.h"
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#include "libc/sysv/consts/clock.h"
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#include "libc/sysv/consts/ipproto.h"
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#include "libc/sysv/consts/ipv6.h"
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#include "libc/sysv/consts/msg.h"
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#include "libc/sysv/consts/poll.h"
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#include "libc/sysv/consts/sock.h"
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#include "libc/sysv/consts/tcp.h"
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#include "libc/thread/thread.h"
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#include "lookup.internal.h"
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asm(".ident\t\"\\n\\n\
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Musl libc (MIT License)\\n\
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Copyright 2005-2014 Rich Felker, et. al.\"");
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asm(".include \"libc/disclaimer.inc\"");
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static void cleanup(void *p)
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{
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struct pollfd *pfd = p;
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for (int i=0; pfd[i].fd >= -1; i++)
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if (pfd[i].fd >= 0)
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close(pfd[i].fd);
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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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if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0 && errno == ENOSYS)
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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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static int start_tcp(struct pollfd *pfd, int family, const void *sa, socklen_t sl, const unsigned char *q, int ql)
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{
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struct msghdr mh = {
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.msg_name = (void *)sa,
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.msg_namelen = sl,
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.msg_iovlen = 2,
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.msg_iov = (struct iovec [2]){
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{ .iov_base = (uint8_t[]){ ql>>8, ql }, .iov_len = 2 },
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{ .iov_base = (void *)q, .iov_len = ql } }
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};
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int r;
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int fd = socket(family, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
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pfd->fd = fd;
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pfd->events = POLLOUT;
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if (IsLinux() &&
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!setsockopt(fd, IPPROTO_TCP, TCP_FASTOPEN_CONNECT,
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&(int){1}, sizeof(int))) {
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r = sendmsg(fd, &mh, MSG_FASTOPEN|MSG_NOSIGNAL);
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if (r == ql+2) pfd->events = POLLIN;
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if (r >= 0) return r;
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if (errno == EINPROGRESS) return 0;
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}
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r = connect(fd, sa, sl);
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if (!r || errno == EINPROGRESS) return 0;
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close(fd);
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pfd->fd = -1;
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return -1;
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}
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static void step_mh(struct msghdr *mh, size_t n)
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{
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/* Adjust iovec in msghdr to skip first n bytes. */
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while (mh->msg_iovlen && n >= mh->msg_iov->iov_len) {
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n -= mh->msg_iov->iov_len;
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mh->msg_iov++;
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mh->msg_iovlen--;
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}
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if (!mh->msg_iovlen) return;
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mh->msg_iov->iov_base = (char *)mh->msg_iov->iov_base + n;
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mh->msg_iov->iov_len -= n;
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}
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/* Internal contract for __res_msend[_rc]: asize must be >=512, nqueries
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* must be sufficiently small to be safe as VLA size. In practice it's
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* either 1 or 2, anyway. */
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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 = 0;
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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[nqueries+2];
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int qpos[nqueries], apos[nqueries];
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unsigned char alen_buf[nqueries][2];
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int r;
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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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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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for (i=0; i<nns && conf->ns[nns].family == AF_INET6; i++);
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if (i==nns) {
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pthread_setcancelstate(cs, 0);
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return -1;
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}
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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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sl = sizeof sa.sin;
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}
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/* Convert any IPv4 addresses in a mixed environment to v4-mapped */
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if (fd >= 0 && 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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sa.sin.sin_family = family;
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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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for (i=0; i<nqueries; i++) pfd[i].fd = -1;
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pfd[nqueries].fd = fd;
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pfd[nqueries].events = POLLIN;
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pfd[nqueries+1].fd = -2;
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pthread_cleanup_push(cleanup, pfd);
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pthread_setcancelstate(cs, 0);
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memset(alens, 0, sizeof *alens * nqueries);
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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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/* This is the loop exit condition: that all queries
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* have an accepted answer. */
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for (i=0; i<nqueries && alens[i]>0; i++);
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if (i==nqueries) break;
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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, nqueries+1, t1+retry_interval-t2) <= 0) continue;
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while (next < nqueries) {
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struct msghdr mh = {
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.msg_name = (void *)&sa,
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.msg_namelen = sl,
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.msg_iovlen = 1,
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.msg_iov = (struct iovec []){
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{ .iov_base = (void *)answers[next],
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.iov_len = asize }
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}
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};
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rlen = recvmsg(fd, &mh, 0);
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if (rlen < 0) break;
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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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/* Ignore further UDP if all slots full or TCP-mode */
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if (next == nqueries) pfd[nqueries].events = 0;
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/* If answer is truncated (TC bit), fallback to TCP */
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if ((answers[i][2] & 2) || (mh.msg_flags & MSG_TRUNC)) {
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alens[i] = -1;
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pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, 0);
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r = start_tcp(pfd+i, family, ns+j, sl, queries[i], qlens[i]);
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pthread_setcancelstate(cs, 0);
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if (r >= 0) {
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qpos[i] = r;
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apos[i] = 0;
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}
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continue;
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}
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}
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for (i=0; i<nqueries; i++) {
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if (pfd[i].revents & POLLOUT) {
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struct msghdr mh = {
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.msg_iovlen = 2,
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.msg_iov = (struct iovec [2]){
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{ .iov_base = (uint8_t[]){ qlens[i]>>8, qlens[i] }, .iov_len = 2 },
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{ .iov_base = (void *)queries[i], .iov_len = qlens[i] } }
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};
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step_mh(&mh, qpos[i]);
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r = sendmsg(pfd[i].fd, &mh, MSG_NOSIGNAL);
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if (r < 0) goto out;
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qpos[i] += r;
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if (qpos[i] == qlens[i]+2)
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pfd[i].events = POLLIN;
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}
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}
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for (i=0; i<nqueries; i++) {
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if (pfd[i].revents & POLLIN) {
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struct msghdr mh = {
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.msg_iovlen = 2,
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.msg_iov = (struct iovec [2]){
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{ .iov_base = alen_buf[i], .iov_len = 2 },
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{ .iov_base = answers[i], .iov_len = asize } }
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};
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step_mh(&mh, apos[i]);
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r = recvmsg(pfd[i].fd, &mh, 0);
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if (r <= 0) goto out;
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apos[i] += r;
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if (apos[i] < 2) continue;
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int alen = alen_buf[i][0]*256 + alen_buf[i][1];
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if (alen < 13) goto out;
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if (apos[i] < alen+2 && apos[i] < asize+2)
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continue;
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int rcode = answers[i][3] & 15;
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if (rcode != 0 && rcode != 3)
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goto out;
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/* Storing the length here commits the accepted answer.
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* Immediately close TCP socket so as not to consume
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* resources we no longer need. */
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alens[i] = alen;
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close(pfd[i].fd);
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pfd[i].fd = -1;
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}
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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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/* Disregard any incomplete TCP results */
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for (i=0; i<nqueries; i++) if (alens[i]<0) alens[i] = 0;
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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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