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e16a7d8f3b
`et` means `expandtab`. ```sh rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\) et\(.*\) :vi/vi: \1 xoet\2:vi/' rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\)noet\(.*\):vi/vi: \1et\2 :vi/' rg 'vi: .* :vi' -l -0 | \ xargs -0 sed -i '' 's/vi: \(.*\)xoet\(.*\):vi/vi: \1noet\2:vi/' ```
114 lines
4.8 KiB
C
114 lines
4.8 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/dns/consts.h"
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#include "libc/dns/dns.h"
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#include "libc/dns/dnsheader.h"
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#include "libc/dns/dnsquestion.h"
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#include "libc/dns/resolvconf.h"
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#include "libc/serialize.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sock/internal.h"
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#include "libc/sock/sock.h"
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#include "libc/sock/struct/sockaddr.h"
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#include "libc/stdio/rand.h"
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#include "libc/stdio/stdio.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/ipproto.h"
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#include "libc/sysv/consts/sock.h"
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#include "libc/sysv/errfuns.h"
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#define kMsgMax 512
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/**
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* Queries Domain Name System for address associated with name.
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*
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* @param resolvconf can be GetResolvConf()
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* @param af can be AF_INET, AF_UNSPEC
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* @param name can be a local or fully-qualified hostname
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* @param addr should point to a struct sockaddr_in; if this function
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* succeeds, its sin_family and sin_addr fields will be modified
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* @param addrsize is the byte size of addr
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* @return number of matches found, or -1 w/ errno
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* @error EAFNOSUPPORT. ENETDOWN, ENAMETOOLONG, EBADMSG
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*/
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int ResolveDns(const struct ResolvConf *resolvconf, int af, const char *name,
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struct sockaddr *addr, uint32_t addrsize) {
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int rc, fd, n;
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struct DnsQuestion q;
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struct DnsHeader h, h2;
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struct sockaddr_in *a4;
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uint8_t *p, *pe, msg[512];
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uint16_t rtype, rclass, rdlength;
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if (addrsize < kMinSockaddr4Size) return einval();
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if (af != AF_INET && af != AF_UNSPEC) return eafnosupport();
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if (!resolvconf->nameservers.i) return 0;
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bzero(&h, sizeof(h));
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rc = ebadmsg();
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h.id = _rand64();
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h.bf1 = 1; /* recursion desired */
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h.qdcount = 1;
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q.qname = name;
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q.qtype = DNS_TYPE_A;
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q.qclass = DNS_CLASS_IN;
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bzero(msg, sizeof(msg));
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SerializeDnsHeader(msg, &h);
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if ((n = SerializeDnsQuestion(msg + 12, 500, &q)) == -1) return -1;
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if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) return -1;
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if (sendto(fd, msg, 12 + n, 0, (struct sockaddr *)resolvconf->nameservers.p,
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sizeof(*resolvconf->nameservers.p)) == 12 + n &&
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(n = read(fd, msg, 512)) >= 12) {
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DeserializeDnsHeader(&h2, msg);
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if (h2.id == h.id) {
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rc = 0;
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p = msg + 12;
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pe = msg + n;
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while (p < pe && h2.qdcount--) {
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p += strnlen((char *)p, pe - p) + 1 + 4;
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}
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while (p < pe && h2.ancount--) {
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if ((p[0] & 0xc0) == 0xc0) { /* name pointer */
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p += 2;
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} else {
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p += strnlen((char *)p, pe - p) + 1;
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}
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if (p + 10 <= pe) {
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rtype = READ16BE(p);
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rclass = READ16BE(p + 2);
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// ttl = READ32BE(p + 4);
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rdlength = READ16BE(p + 8);
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if (p + 10 + rdlength <= pe && rdlength == 4 &&
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rclass == DNS_CLASS_IN && rtype == DNS_TYPE_A) {
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rc = 1;
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a4 = (struct sockaddr_in *)addr;
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a4->sin_family = AF_INET;
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memcpy(&a4->sin_addr.s_addr, p + 10, 4);
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break;
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}
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p += 10 + rdlength;
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}
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}
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}
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}
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close(fd);
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return rc;
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}
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