freebsd-dev/contrib/dma/dns.c
2021-09-22 11:10:58 +02:00

294 lines
6.6 KiB
C

/*
* Copyright (c) 2008-2014, Simon Schubert <2@0x2c.org>.
* Copyright (c) 2008 The DragonFly Project. All rights reserved.
*
* This code is derived from software contributed to The DragonFly Project
* by Simon Schubert <2@0x2c.org>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name of The DragonFly Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific, prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <string.h>
#include <stdlib.h>
#include "dma.h"
static int
sort_pref(const void *a, const void *b)
{
const struct mx_hostentry *ha = a, *hb = b;
int v;
/* sort increasing by preference primarily */
v = ha->pref - hb->pref;
if (v != 0)
return (v);
/* sort PF_INET6 before PF_INET */
v = - (ha->ai.ai_family - hb->ai.ai_family);
return (v);
}
static int
add_host(int pref, const char *host, int port, struct mx_hostentry **he, size_t *ps)
{
struct addrinfo hints, *res, *res0 = NULL;
char servname[10];
struct mx_hostentry *p;
const int count_inc = 10;
memset(&hints, 0, sizeof(hints));
hints.ai_family = PF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
snprintf(servname, sizeof(servname), "%d", port);
switch (getaddrinfo(host, servname, &hints, &res0)) {
case 0:
break;
case EAI_AGAIN:
case EAI_NONAME:
/*
* EAI_NONAME gets returned for:
* SMARTHOST set but DNS server not reachable -> defer
* SMARTHOST set but DNS server returns "host does not exist"
* -> buggy configuration
* -> either defer or bounce would be ok -> defer
* MX entry was returned by DNS server but name doesn't resolve
* -> hopefully transient situation -> defer
* all other DNS problems should have been caught earlier
* in dns_get_mx_list().
*/
goto out;
default:
return(-1);
}
for (res = res0; res != NULL; res = res->ai_next) {
if (*ps + 1 >= roundup(*ps, count_inc)) {
size_t newsz = roundup(*ps + 2, count_inc);
*he = reallocf(*he, newsz * sizeof(**he));
if (*he == NULL)
goto out;
}
p = &(*he)[*ps];
strlcpy(p->host, host, sizeof(p->host));
p->pref = pref;
p->ai = *res;
p->ai.ai_addr = NULL;
bcopy(res->ai_addr, &p->sa, p->ai.ai_addrlen);
getnameinfo((struct sockaddr *)&p->sa, p->ai.ai_addrlen,
p->addr, sizeof(p->addr),
NULL, 0, NI_NUMERICHOST);
(*ps)++;
}
freeaddrinfo(res0);
return (0);
out:
if (res0 != NULL)
freeaddrinfo(res0);
return (1);
}
int
dns_get_mx_list(const char *host, int port, struct mx_hostentry **he, int no_mx)
{
char outname[MAXDNAME];
ns_msg msg;
ns_rr rr;
const char *searchhost;
const unsigned char *cp;
unsigned char *ans;
struct mx_hostentry *hosts = NULL;
size_t nhosts = 0;
size_t anssz;
int pref;
int cname_recurse;
int have_mx = 0;
int err;
int i;
res_init();
searchhost = host;
cname_recurse = 0;
anssz = 65536;
ans = malloc(anssz);
if (ans == NULL)
return (1);
if (no_mx)
goto out;
repeat:
err = res_search(searchhost, ns_c_in, ns_t_mx, ans, anssz);
if (err < 0) {
switch (h_errno) {
case NO_DATA:
/*
* Host exists, but no MX (or CNAME) entry.
* Not an error, use host name instead.
*/
goto out;
case TRY_AGAIN:
/* transient error */
goto transerr;
case NO_RECOVERY:
case HOST_NOT_FOUND:
default:
errno = ENOENT;
goto err;
}
}
if (!ns_initparse(ans, anssz, &msg))
goto transerr;
switch (ns_msg_getflag(msg, ns_f_rcode)) {
case ns_r_noerror:
break;
case ns_r_nxdomain:
goto err;
default:
goto transerr;
}
for (i = 0; i < ns_msg_count(msg, ns_s_an); i++) {
if (ns_parserr(&msg, ns_s_an, i, &rr))
goto transerr;
cp = ns_rr_rdata(rr);
switch (ns_rr_type(rr)) {
case ns_t_mx:
have_mx = 1;
pref = ns_get16(cp);
cp += 2;
err = ns_name_uncompress(ns_msg_base(msg), ns_msg_end(msg),
cp, outname, sizeof(outname));
if (err < 0)
goto transerr;
err = add_host(pref, outname, port, &hosts, &nhosts);
if (err == -1)
goto err;
break;
case ns_t_cname:
err = ns_name_uncompress(ns_msg_base(msg), ns_msg_end(msg),
cp, outname, sizeof(outname));
if (err < 0)
goto transerr;
/* Prevent a CNAME loop */
if (cname_recurse++ > 10)
goto err;
searchhost = outname;
goto repeat;
default:
break;
}
}
out:
err = 0;
if (0) {
transerr:
if (nhosts == 0)
err = 1;
}
if (0) {
err:
err = -1;
}
free(ans);
if (err == 0) {
if (!have_mx) {
/*
* If we didn't find any MX, use the hostname instead.
*/
err = add_host(0, host, port, &hosts, &nhosts);
} else if (nhosts == 0) {
/*
* We did get MX, but couldn't resolve any of them
* due to transient errors.
*/
err = 1;
}
}
if (nhosts > 0) {
qsort(hosts, nhosts, sizeof(*hosts), sort_pref);
/* terminate list */
*hosts[nhosts].host = 0;
} else {
if (hosts != NULL)
free(hosts);
hosts = NULL;
}
*he = hosts;
return (err);
}
#if defined(TESTING)
int
main(int argc, char **argv)
{
struct mx_hostentry *he, *p;
int err;
err = dns_get_mx_list(argv[1], 53, &he, 0);
if (err)
return (err);
for (p = he; *p->host != 0; p++) {
printf("%d\t%s\t%s\n", p->pref, p->host, p->addr);
}
return (0);
}
#endif