cosmopolitan/libc/dns/dnsheader.c

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2020-06-15 14:18:57 +00:00
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
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Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
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*/
#include "libc/bits/bits.h"
#include "libc/dns/dnsheader.h"
#include "libc/sysv/errfuns.h"
/**
* Serializes DNS message header to wire.
*
* @return number of bytes written (always 12) or -1 w/ errno
* @see pascalifydnsname()
*/
int serializednsheader(uint8_t *buf, size_t size,
const struct DnsHeader header) {
if (size < 12) return enospc();
buf[0x0] = header.id >> 010u;
buf[0x1] = header.id >> 000u;
buf[0x2] = header.bf1;
buf[0x3] = header.bf2;
buf[0x4] = header.qdcount >> 010u;
buf[0x5] = header.qdcount >> 000u;
buf[0x6] = header.ancount >> 010u;
buf[0x7] = header.ancount >> 000u;
buf[0x8] = header.nscount >> 010u;
buf[0x9] = header.nscount >> 000u;
buf[0xa] = header.arcount >> 010u;
buf[0xb] = header.arcount >> 000u;
return 12;
}
/**
* Serializes DNS message header to wire.
*
* @return number of bytes read (always 12) or -1 w/ errno
*/
int deserializednsheader(struct DnsHeader *header, const uint8_t *buf,
size_t size) {
if (size < 12) return ebadmsg();
header->id = read16be(buf + 0);
header->bf1 = buf[2];
header->bf2 = buf[3];
header->qdcount = read16be(buf + 4);
header->ancount = read16be(buf + 6);
header->nscount = read16be(buf + 8);
header->arcount = read16be(buf + 10);
return 12;
}