cosmopolitan/libc/dns/getresolvconf.c

63 lines
3.0 KiB
C

/*-*- 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 │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/pushpop.h"
#include "libc/dce.h"
#include "libc/dns/resolvconf.h"
#include "libc/fmt/fmt.h"
#include "libc/macros.h"
#include "libc/runtime/runtime.h"
#include "libc/sock/sock.h"
#include "libc/stdio/stdio.h"
static struct ResolvConf *g_resolvconf;
static struct ResolvConfInitialStaticMemory {
struct ResolvConf rv;
struct sockaddr_in nameservers[3];
} g_resolvconf_init;
/**
* Returns singleton with DNS server address.
*/
const struct ResolvConf *getresolvconf(void) {
int rc;
FILE *f;
struct ResolvConfInitialStaticMemory *init = &g_resolvconf_init;
if (!g_resolvconf) {
g_resolvconf = &init->rv;
pushmov(&init->rv.nameservers.n, ARRAYLEN(init->nameservers));
init->rv.nameservers.p = init->nameservers;
__cxa_atexit(freeresolvconf, &g_resolvconf, NULL);
if (!IsWindows()) {
if ((f = fopen("/etc/resolv.conf", "r"))) {
rc = parseresolvconf(g_resolvconf, f);
} else {
rc = -1;
}
fclose(f);
} else {
rc = getntnameservers(g_resolvconf);
}
if (rc == -1 && !IsTiny()) {
fprintf(stderr, "%s: %m\n", "nameserver discovery failed");
}
}
return g_resolvconf;
}