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/* udns_rr_srv.c
parse/query SRV IN (rfc2782) records
Copyright (C) 2005 Michael Tokarev <mjt@corpit.ru>
This file is part of UDNS library, an async DNS stub resolver.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library, in file named COPYING.LGPL; if not,
write to the Free Software Foundation, Inc., 59 Temple Place,
Suite 330, Boston, MA 02111-1307 USA
Copyright 2005 Thadeu Lima de Souza Cascardo <cascardo@minaslivre.org>
2005-09-11:
Changed MX parser file into a SRV parser file
*/
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include "udns.h"
int
dns_parse_srv(dnscc_t *qdn, dnscc_t *pkt, dnscc_t *cur, dnscc_t *end,
void **result) {
struct dns_rr_srv *ret;
struct dns_parse p;
struct dns_rr rr;
int r, l;
char *sp;
dnsc_t srv[DNS_MAXDN];
assert(dns_get16(cur+2) == DNS_C_IN && dns_get16(cur+0) == DNS_T_SRV);
/* first, validate the answer and count size of the result */
l = 0;
dns_initparse(&p, qdn, pkt, cur, end);
while((r = dns_nextrr(&p, &rr)) > 0) {
cur = rr.dnsrr_dptr + 6;
r = dns_getdn(pkt, &cur, end, srv, sizeof(srv));
if (r <= 0 || cur != rr.dnsrr_dend)
return DNS_E_PROTOCOL;
l += dns_dntop_size(srv);
}
if (r < 0)
return DNS_E_PROTOCOL;
if (!p.dnsp_nrr)
return DNS_E_NODATA;
/* next, allocate and set up result */
l += dns_stdrr_size(&p);
ret = malloc(sizeof(*ret) + sizeof(struct dns_srv) * p.dnsp_nrr + l);
if (!ret)
return DNS_E_NOMEM;
ret->dnssrv_nrr = p.dnsp_nrr;
ret->dnssrv_srv = (struct dns_srv *)(ret+1);
/* and 3rd, fill in result, finally */
sp = (char*)(ret->dnssrv_srv + p.dnsp_nrr);
for (dns_rewind(&p, qdn), r = 0; dns_nextrr(&p, &rr); ++r) {
ret->dnssrv_srv[r].name = sp;
cur = rr.dnsrr_dptr;
ret->dnssrv_srv[r].priority = dns_get16(cur);
ret->dnssrv_srv[r].weight = dns_get16(cur+2);
ret->dnssrv_srv[r].port = dns_get16(cur+4);
cur += 6;
dns_getdn(pkt, &cur, end, srv, sizeof(srv));
sp += dns_dntop(srv, sp, DNS_MAXNAME);
}
dns_stdrr_finish((struct dns_rr_null *)ret, sp, &p);
*result = ret;
return 0;
}
/* Add a single service or proto name prepending an undescore (_),
* according to rfc2782 rules.
* Return 0 or the label length.
* Routing assumes dn holds enouth space for a single DN label. */
static int add_sname(dnsc_t *dn, const char *sn) {
int l = dns_ptodn(sn, 0, dn + 1, DNS_MAXLABEL-1, NULL);
if (l <= 1 || l - 2 != dn[1])
/* Should we really check if sn is exactly one label? Do we care? */
return 0;
dn[0] = l - 1;
dn[1] = '_';
return l;
}
/* Construct a domain name for SRV query from the given name, service and proto.
* The code allows any combinations of srv and proto (both are non-NULL,
* both NULL, or either one is non-NULL). Whenever it makes any sense or not
* is left as an exercise to programmer.
* Return negative value on error (malformed query) or addition query flag(s).
*/
static int
build_srv_dn(dnsc_t *dn, const char *name, const char *srv, const char *proto)
{
int p = 0, l, isabs;
if (srv) {
l = add_sname(dn + p, srv);
if (!l)
return -1;
p += l;
}
if (proto) {
l = add_sname(dn + p, proto);
if (!l)
return -1;
p += l;
}
l = dns_ptodn(name, 0, dn + p, DNS_MAXDN - p, &isabs);
if (l < 0)
return -1;
return isabs ? DNS_NOSRCH : 0;
}
struct dns_query *
dns_submit_srv(struct dns_ctx *ctx,
const char *name, const char *srv, const char *proto,
int flags, dns_query_srv_fn *cbck, void *data) {
dnsc_t dn[DNS_MAXDN];
int r = build_srv_dn(dn, name, srv, proto);
if (r < 0) {
dns_setstatus (ctx, DNS_E_BADQUERY);
return NULL;
}
return
dns_submit_dn(ctx, dn, DNS_C_IN, DNS_T_SRV, flags | r,
dns_parse_srv, (dns_query_fn *)cbck, data);
}
struct dns_rr_srv *
dns_resolve_srv(struct dns_ctx *ctx,
const char *name, const char *srv, const char *proto, int flags)
{
dnsc_t dn[DNS_MAXDN];
int r = build_srv_dn(dn, name, srv, proto);
if (r < 0) {
dns_setstatus(ctx, DNS_E_BADQUERY);
return NULL;
}
return (struct dns_rr_srv *)
dns_resolve_dn(ctx, dn, DNS_C_IN, DNS_T_SRV, flags | r, dns_parse_srv);
}
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