/***
This file is part of avahi.
avahi 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.
avahi 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 avahi; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <avahi-common/defs.h>
#include <avahi-common/domain.h>
#include "avahi-common/avahi-malloc.h"
#include "dns.h"
#include "log.h"
AvahiDnsPacket* avahi_dns_packet_new(unsigned mtu) {
AvahiDnsPacket *p;
size_t max_size;
if (mtu <= 0)
max_size = AVAHI_DNS_PACKET_SIZE_MAX;
else if (mtu >= AVAHI_DNS_PACKET_EXTRA_SIZE)
max_size = mtu - AVAHI_DNS_PACKET_EXTRA_SIZE;
else
max_size = 0;
if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE)
max_size = AVAHI_DNS_PACKET_HEADER_SIZE;
if (!(p = avahi_malloc(sizeof(AvahiDnsPacket) + max_size)))
return p;
p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
p->max_size = max_size;
p->name_table = NULL;
p->data = NULL;
memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size);
return p;
}
AvahiDnsPacket* avahi_dns_packet_new_query(unsigned mtu) {
AvahiDnsPacket *p;
if (!(p = avahi_dns_packet_new(mtu)))
return NULL;
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
return p;
}
AvahiDnsPacket* avahi_dns_packet_new_response(unsigned mtu, int aa) {
AvahiDnsPacket *p;
if (!(p = avahi_dns_packet_new(mtu)))
return NULL;
avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, aa, 0, 0, 0, 0, 0, 0, 0));
return p;
}
AvahiDnsPacket* avahi_dns_packet_new_reply(AvahiDnsPacket* p, unsigned mtu, int copy_queries, int aa) {
AvahiDnsPacket *r;
assert(p);
if (!(r = avahi_dns_packet_new_response(mtu, aa)))
return NULL;
if (copy_queries) {
unsigned saved_rindex;
uint32_t n;
saved_rindex = p->rindex;
p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
for (n = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT); n > 0; n--) {
AvahiKey *k;
int unicast_response;
if ((k = avahi_dns_packet_consume_key(p, &unicast_response))) {
avahi_dns_packet_append_key(r, k, unicast_response);
avahi_key_unref(k);
}
}
p->rindex = saved_rindex;
avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_QDCOUNT, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT));
}
avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_ID, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_ID));
avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_FLAGS,
(avahi_dns_packet_get_field(r, AVAHI_DNS_FIELD_FLAGS) & ~AVAHI_DNS_FLAG_OPCODE) |
(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_OPCODE));
return r;
}
void avahi_dns_packet_free(AvahiDnsPacket *p) {
assert(p);
if (p->name_table)
avahi_hashmap_free(p->name_table);
avahi_free(p);
}
void avahi_dns_packet_set_field(AvahiDnsPacket *p, unsigned idx, uint16_t v) {
assert(p);
assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx] = htons(v);
}
uint16_t avahi_dns_packet_get_field(AvahiDnsPacket *p, unsigned idx) {
assert(p);
assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
return ntohs(((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx]);
}
void avahi_dns_packet_inc_field(AvahiDnsPacket *p, unsigned idx) {
assert(p);
assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
avahi_dns_packet_set_field(p, idx, avahi_dns_packet_get_field(p, idx) + 1);
}
static void name_table_cleanup(void *key, void *value, void *user_data) {
AvahiDnsPacket *p = user_data;
if ((uint8_t*) value >= AVAHI_DNS_PACKET_DATA(p) + p->size)
avahi_hashmap_remove(p->name_table, key);
}
void avahi_dns_packet_cleanup_name_table(AvahiDnsPacket *p) {
if (p->name_table)
avahi_hashmap_foreach(p->name_table, name_table_cleanup, p);
}
uint8_t* avahi_dns_packet_append_name(AvahiDnsPacket *p, const char *name) {
uint8_t *d, *saved_ptr = NULL;
size_t saved_size;
assert(p);
assert(name);
saved_size = p->size;
saved_ptr = avahi_dns_packet_extend(p, 0);
while (*name) {
uint8_t* prev;
const char *pname;
char label[64], *u;
/* Check whether we can compress this name. */
if (p->name_table && (prev = avahi_hashmap_lookup(p->name_table, name))) {
unsigned idx;
assert(prev >= AVAHI_DNS_PACKET_DATA(p));
idx = (unsigned) (prev - AVAHI_DNS_PACKET_DATA(p));
assert(idx < p->size);
if (idx < 0x4000) {
uint8_t *t;
if (!(t = (uint8_t*) avahi_dns_packet_extend(p, sizeof(uint16_t))))
return NULL;
t[0] = (uint8_t) ((0xC000 | idx) >> 8);
t[1] = (uint8_t) idx;
return saved_ptr;
}
}
pname = name;
if (!(avahi_unescape_label(&name, label, sizeof(label))))
goto fail;
if (!(d = avahi_dns_packet_append_string(p, label)))
goto fail;
if (!p->name_table)
/* This works only for normalized domain names */
p->name_table = avahi_hashmap_new(avahi_string_hash, avahi_string_equal, avahi_free, NULL);
if (!(u = avahi_strdup(pname)))
avahi_log_error("avahi_strdup() failed.");
else
avahi_hashmap_insert(p->name_table, u, d);
}
if (!(d = avahi_dns_packet_extend(p, 1)))
goto fail;
*d = 0;
return saved_ptr;
fail:
p->size = saved_size;
avahi_dns_packet_cleanup_name_table(p);
return NULL;
}
uint8_t* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, uint16_t v) {
uint8_t *d;
assert(p);
if (!(d = avahi_dns_packet_extend(p, sizeof(uint16_t))))
return NULL;
d[0] = (uint8_t) (v >> 8);
d[1] = (uint8_t) v;
return d;
}
uint8_t *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, uint32_t v) {
uint8_t *d;
assert(p);
if (!(d = avahi_dns_packet_extend(p, sizeof(uint32_t))))
return NULL;
d[0] = (uint8_t) (v >> 24);
d[1] = (uint8_t) (v >> 16);
d[2] = (uint8_t) (v >> 8);
d[3] = (uint8_t) v;
return d;
}
uint8_t *avahi_dns_packet_append_bytes(AvahiDnsPacket *p, const void *b, size_t l) {
uint8_t* d;
assert(p);
assert(b);
assert(l);
if (!(d = avahi_dns_packet_extend(p, l)))
return NULL;
memcpy(d, b, l);
return d;
}
uint8_t* avahi_dns_packet_append_string(AvahiDnsPacket *p, const char *s) {
uint8_t* d;
size_t k;
assert(p);
assert(s);
if ((k = strlen(s)) >= 255)
k = 255;
if (!(d = avahi_dns_packet_extend(p, k+1)))
return NULL;
*d = (uint8_t) k;
memcpy(d+1, s, k);
return d;
}
uint8_t *avahi_dns_packet_extend(AvahiDnsPacket *p, size_t l) {
uint8_t *d;
assert(p);
if (p->size+l > p->max_size)
return NULL;
d = AVAHI_DNS_PACKET_DATA(p) + p->size;
p->size += l;
return d;
}
int avahi_dns_packet_check_valid(AvahiDnsPacket *p) {
uint16_t flags;
assert(p);
if (p->size < AVAHI_DNS_PACKET_HEADER_SIZE)
return -1;
flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
if (flags & AVAHI_DNS_FLAG_OPCODE)
return -1;
return 0;
}
int avahi_dns_packet_check_valid_multicast(AvahiDnsPacket *p) {
uint16_t flags;
assert(p);
if (avahi_dns_packet_check_valid(p) < 0)
return -1;
flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
if (flags & AVAHI_DNS_FLAG_RCODE)
return -1;
return 0;
}
int avahi_dns_packet_is_query(AvahiDnsPacket *p) {
assert(p);
return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR);
}
static int consume_labels(AvahiDnsPacket *p, unsigned idx, char *ret_name, size_t l) {
int ret = 0;
int compressed = 0;
int first_label = 1;
unsigned label_ptr;
int i;
assert(p && ret_name && l);
for (i = 0; i < AVAHI_DNS_LABELS_MAX; i++) {
uint8_t n;
if (idx+1 > p->size)
return -1;
n = AVAHI_DNS_PACKET_DATA(p)[idx];
if (!n) {
idx++;
if (!compressed)
ret++;
if (l < 1)
return -1;
*ret_name = 0;
return ret;
} else if (n <= 63) {
/* Uncompressed label */
idx++;
if (!compressed)
ret++;
if (idx + n > p->size)
return -1;
if ((size_t) n + 1 > l)
return -1;
if (!first_label) {
*(ret_name++) = '.';
l--;
} else
first_label = 0;
if (!(avahi_escape_label((char*) AVAHI_DNS_PACKET_DATA(p) + idx, n, &ret_name, &l)))
return -1;
idx += n;
if (!compressed)
ret += n;
} else if ((n & 0xC0) == 0xC0) {
/* Compressed label */
if (idx+2 > p->size)
return -1;
label_ptr = ((unsigned) (AVAHI_DNS_PACKET_DATA(p)[idx] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[idx+1];
if ((label_ptr < AVAHI_DNS_PACKET_HEADER_SIZE) || (label_ptr >= idx))
return -1;
idx = label_ptr;
if (!compressed)
ret += 2;
compressed = 1;
} else
return -1;
}
return -1;
}
int avahi_dns_packet_consume_name(AvahiDnsPacket *p, char *ret_name, size_t l) {
int r;
if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)
return -1;
p->rindex += r;
return 0;
}
int avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, uint16_t *ret_v) {
uint8_t *d;
assert(p);
assert(ret_v);
if (p->rindex + sizeof(uint16_t) > p->size)
return -1;
d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);
*ret_v = (d[0] << 8) | d[1];
p->rindex += sizeof(uint16_t);
return 0;
}
int avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, uint32_t *ret_v) {
uint8_t* d;
assert(p);
assert(ret_v);
if (p->rindex + sizeof(uint32_t) > p->size)
return -1;
d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);
*ret_v = (d[0] << 24) | (d[1] << 16) | (d[2] << 8) | d[3];
p->rindex += sizeof(uint32_t);
return 0;
}
int avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, void * ret_data, size_t l) {
assert(p);
assert(ret_data);
assert(l > 0);
if (p->rindex + l > p->size)
return -1;
memcpy(ret_data, AVAHI_DNS_PACKET_DATA(p) + p->rindex, l);
p->rindex += l;
return 0;
}
int avahi_dns_packet_consume_string(AvahiDnsPacket *p, char *ret_string, size_t l) {
size_t k;
assert(p);
assert(ret_string);
assert(l > 0);
if (p->rindex >= p->size)
return -1;
k = AVAHI_DNS_PACKET_DATA(p)[p->rindex];
if (p->rindex+1+k > p->size)
return -1;
if (l > k+1)
l = k+1;
memcpy(ret_string, AVAHI_DNS_PACKET_DATA(p)+p->rindex+1, l-1);
ret_string[l-1] = 0;
p->rindex += 1+k;
return 0;
}
const void* avahi_dns_packet_get_rptr(AvahiDnsPacket *p) {
assert(p);
if (p->rindex > p->size)
return NULL;
return AVAHI_DNS_PACKET_DATA(p) + p->rindex;
}
int avahi_dns_packet_skip(AvahiDnsPacket *p, size_t length) {
assert(p);
if (p->rindex + length > p->size)
return -1;
p->rindex += length;
return 0;
}
static int parse_rdata(AvahiDnsPacket *p, AvahiRecord *r, uint16_t rdlength) {
char buf[AVAHI_DOMAIN_NAME_MAX];
const void* start;
assert(p);
assert(r);
start = avahi_dns_packet_get_rptr(p);
switch (r->key->type) {
case AVAHI_DNS_TYPE_PTR:
case AVAHI_DNS_TYPE_CNAME:
case AVAHI_DNS_TYPE_NS:
if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
return -1;
r->data.ptr.name = avahi_strdup(buf);
break;
case AVAHI_DNS_TYPE_SRV:
if (avahi_dns_packet_consume_uint16(p, &r->data.srv.priority) < 0 ||
avahi_dns_packet_consume_uint16(p, &r->data.srv.weight) < 0 ||
avahi_dns_packet_consume_uint16(p, &r->data.srv.port) < 0 ||
avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
return -1;
r->data.srv.name = avahi_strdup(buf);
break;
case AVAHI_DNS_TYPE_HINFO:
if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
return -1;
r->data.hinfo.cpu = avahi_strdup(buf);
if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
return -1;
r->data.hinfo.os = avahi_strdup(buf);
break;
case AVAHI_DNS_TYPE_TXT:
if (rdlength > 0) {
if (avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength, &r->data.txt.string_list) < 0)
return -1;
if (avahi_dns_packet_skip(p, rdlength) < 0)
return -1;
} else
r->data.txt.string_list = NULL;
break;
case AVAHI_DNS_TYPE_A:
/* avahi_log_debug("A"); */
if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0)
return -1;
break;
case AVAHI_DNS_TYPE_AAAA:
/* avahi_log_debug("aaaa"); */
if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0)
return -1;
break;
default:
/* avahi_log_debug("generic"); */
if (rdlength > 0) {
r->data.generic.data = avahi_memdup(avahi_dns_packet_get_rptr(p), rdlength);
r->data.generic.size = rdlength;
if (avahi_dns_packet_skip(p, rdlength) < 0)
return -1;
}
break;
}
/* Check if we read enough data */
if ((const uint8_t*) avahi_dns_packet_get_rptr(p) - (const uint8_t*) start != rdlength)
return -1;
return 0;
}
AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, int *ret_cache_flush) {
char name[AVAHI_DOMAIN_NAME_MAX];
uint16_t type, class;
uint32_t ttl;
uint16_t rdlength;
AvahiRecord *r = NULL;
assert(p);
if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
avahi_dns_packet_consume_uint16(p, &type) < 0 ||
avahi_dns_packet_consume_uint16(p, &class) < 0 ||
avahi_dns_packet_consume_uint32(p, &ttl) < 0 ||
avahi_dns_packet_consume_uint16(p, &rdlength) < 0 ||
p->rindex + rdlength > p->size)
goto fail;
if (ret_cache_flush)
*ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH);
class &= ~AVAHI_DNS_CACHE_FLUSH;
if (!(r = avahi_record_new_full(name, class, type, ttl)))
goto fail;
if (parse_rdata(p, r, rdlength) < 0)
goto fail;
if (!avahi_record_is_valid(r))
goto fail;
return r;
fail:
if (r)
avahi_record_unref(r);
return NULL;
}
AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, int *ret_unicast_response) {
char name[256];
uint16_t type, class;
AvahiKey *k;
assert(p);
if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
avahi_dns_packet_consume_uint16(p, &type) < 0 ||
avahi_dns_packet_consume_uint16(p, &class) < 0)
return NULL;
if (ret_unicast_response)
*ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE);
class &= ~AVAHI_DNS_UNICAST_RESPONSE;
if (!(k = avahi_key_new(name, class, type)))
return NULL;
if (!avahi_key_is_valid(k)) {
avahi_key_unref(k);
return NULL;
}
return k;
}
uint8_t* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, int unicast_response) {
uint8_t *t;
size_t size;
assert(p);
assert(k);
size = p->size;
if (!(t = avahi_dns_packet_append_name(p, k->name)) ||
!avahi_dns_packet_append_uint16(p, k->type) ||
!avahi_dns_packet_append_uint16(p, k->clazz | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) {
p->size = size;
avahi_dns_packet_cleanup_name_table(p);
return NULL;
}
return t;
}
static int append_rdata(AvahiDnsPacket *p, AvahiRecord *r) {
assert(p);
assert(r);
switch (r->key->type) {
case AVAHI_DNS_TYPE_PTR:
case AVAHI_DNS_TYPE_CNAME:
case AVAHI_DNS_TYPE_NS:
if (!(avahi_dns_packet_append_name(p, r->data.ptr.name)))
return -1;
break;
case AVAHI_DNS_TYPE_SRV:
if (!avahi_dns_packet_append_uint16(p, r->data.srv.priority) ||
!avahi_dns_packet_append_uint16(p, r->data.srv.weight) ||
!avahi_dns_packet_append_uint16(p, r->data.srv.port) ||
!avahi_dns_packet_append_name(p, r->data.srv.name))
return -1;
break;
case AVAHI_DNS_TYPE_HINFO:
if (!avahi_dns_packet_append_string(p, r->data.hinfo.cpu) ||
!avahi_dns_packet_append_string(p, r->data.hinfo.os))
return -1;
break;
case AVAHI_DNS_TYPE_TXT: {
uint8_t *data;
size_t n;
n = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0);
if (!(data = avahi_dns_packet_extend(p, n)))
return -1;
avahi_string_list_serialize(r->data.txt.string_list, data, n);
break;
}
case AVAHI_DNS_TYPE_A:
if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address)))
return -1;
break;
case AVAHI_DNS_TYPE_AAAA:
if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address)))
return -1;
break;
default:
if (r->data.generic.size)
if (!avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size))
return -1;
break;
}
return 0;
}
uint8_t* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, int cache_flush, unsigned max_ttl) {
uint8_t *t, *l, *start;
size_t size;
assert(p);
assert(r);
size = p->size;
if (!(t = avahi_dns_packet_append_name(p, r->key->name)) ||
!avahi_dns_packet_append_uint16(p, r->key->type) ||
!avahi_dns_packet_append_uint16(p, cache_flush ? (r->key->clazz | AVAHI_DNS_CACHE_FLUSH) : (r->key->clazz &~ AVAHI_DNS_CACHE_FLUSH)) ||
!avahi_dns_packet_append_uint32(p, (max_ttl && r->ttl > max_ttl) ? max_ttl : r->ttl) ||
!(l = avahi_dns_packet_append_uint16(p, 0)))
goto fail;
start = avahi_dns_packet_extend(p, 0);
if (append_rdata(p, r) < 0)
goto fail;
size = avahi_dns_packet_extend(p, 0) - start;
assert(size <= AVAHI_DNS_RDATA_MAX);
/* avahi_log_debug("appended %u", size); */
l[0] = (uint8_t) ((uint16_t) size >> 8);
l[1] = (uint8_t) ((uint16_t) size);
return t;
fail:
p->size = size;
avahi_dns_packet_cleanup_name_table(p);
return NULL;
}
int avahi_dns_packet_is_empty(AvahiDnsPacket *p) {
assert(p);
return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE;
}
size_t avahi_dns_packet_space(AvahiDnsPacket *p) {
assert(p);
assert(p->size <= p->max_size);
return p->max_size - p->size;
}
int avahi_rdata_parse(AvahiRecord *record, const void* rdata, size_t size) {
int ret;
AvahiDnsPacket p;
assert(record);
assert(rdata);
p.data = (void*) rdata;
p.max_size = p.size = size;
p.rindex = 0;
p.name_table = NULL;
ret = parse_rdata(&p, record, size);
assert(!p.name_table);
return ret;
}
size_t avahi_rdata_serialize(AvahiRecord *record, void *rdata, size_t max_size) {
int ret;
AvahiDnsPacket p;
assert(record);
assert(rdata);
assert(max_size > 0);
p.data = (void*) rdata;
p.max_size = max_size;
p.size = p.rindex = 0;
p.name_table = NULL;
ret = append_rdata(&p, record);
if (p.name_table)
avahi_hashmap_free(p.name_table);
if (ret < 0)
return (size_t) -1;
return p.size;
}