diff options
Diffstat (limited to 'avahi-core/dns.c')
| -rw-r--r-- | avahi-core/dns.c | 772 |
1 files changed, 772 insertions, 0 deletions
diff --git a/avahi-core/dns.c b/avahi-core/dns.c new file mode 100644 index 0000000..cc1463a --- /dev/null +++ b/avahi-core/dns.c @@ -0,0 +1,772 @@ +/* $Id$ */ + +/*** + 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 <netinet/in.h> + +#include <stdlib.h> +#include <string.h> +#include <stdio.h> + +#include "dns.h" +#include "util.h" + +AvahiDnsPacket* avahi_dns_packet_new(guint max_size) { + AvahiDnsPacket *p; + + if (max_size <= 0) + max_size = AVAHI_DNS_PACKET_MAX_SIZE; + else if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE) + max_size = AVAHI_DNS_PACKET_HEADER_SIZE; + + p = g_malloc(sizeof(AvahiDnsPacket) + max_size); + p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE; + p->max_size = max_size; + p->name_table = NULL; + + memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size); + return p; +} + +AvahiDnsPacket* avahi_dns_packet_new_query(guint max_size) { + AvahiDnsPacket *p; + + p = avahi_dns_packet_new(max_size); + 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(guint max_size) { + AvahiDnsPacket *p; + + p = avahi_dns_packet_new(max_size); + avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, 0, 0, 0, 0, 0, 0, 0, 0)); + return p; +} + +void avahi_dns_packet_free(AvahiDnsPacket *p) { + g_assert(p); + + if (p->name_table) + g_hash_table_destroy(p->name_table); + + g_free(p); +} + +void avahi_dns_packet_set_field(AvahiDnsPacket *p, guint index, guint16 v) { + g_assert(p); + g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE); + + ((guint16*) AVAHI_DNS_PACKET_DATA(p))[index] = g_htons(v); +} + +guint16 avahi_dns_packet_get_field(AvahiDnsPacket *p, guint index) { + g_assert(p); + g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE); + + return g_ntohs(((guint16*) AVAHI_DNS_PACKET_DATA(p))[index]); +} + +/* Read the first label from string *name, unescape "\" and write it to dest */ +gchar *avahi_unescape_label(gchar *dest, guint size, const gchar **name) { + guint i = 0; + gchar *d; + + g_assert(dest); + g_assert(size > 0); + g_assert(name); + g_assert(*name); + + d = dest; + + for (;;) { + if (i >= size) + return NULL; + + if (**name == '.') { + (*name)++; + break; + } + + if (**name == 0) + break; + + if (**name == '\\') { + (*name) ++; + + if (**name == 0) + break; + } + + *(d++) = *((*name) ++); + i++; + } + + g_assert(i < size); + + *d = 0; + + return dest; +} + +guint8* avahi_dns_packet_append_name(AvahiDnsPacket *p, const gchar *name) { + guint8 *d, *saved_ptr = NULL; + guint saved_size; + + g_assert(p); + g_assert(name); + + saved_size = p->size; + saved_ptr = avahi_dns_packet_extend(p, 0); + + while (*name) { + guint8* prev; + const gchar *pname; + gchar label[64]; + + /* Check whether we can compress this name. */ + + if (p->name_table && (prev = g_hash_table_lookup(p->name_table, name))) { + guint index; + + g_assert(prev >= AVAHI_DNS_PACKET_DATA(p)); + index = (guint) (prev - AVAHI_DNS_PACKET_DATA(p)); + + g_assert(index < p->size); + + if (index < 0x4000) { + guint16 *t; + if (!(t = (guint16*) avahi_dns_packet_extend(p, sizeof(guint16)))) + return NULL; + + *t = g_htons((0xC000 | index)); + return saved_ptr; + } + } + + pname = name; + + if (!(avahi_unescape_label(label, sizeof(label), &name))) + goto fail; + + if (!(d = avahi_dns_packet_append_string(p, label))) + goto fail; + + if (!p->name_table) + p->name_table = g_hash_table_new_full((GHashFunc) avahi_domain_hash, (GEqualFunc) avahi_domain_equal, g_free, NULL); + + g_hash_table_insert(p->name_table, g_strdup(pname), d); + } + + if (!(d = avahi_dns_packet_extend(p, 1))) + goto fail; + + *d = 0; + + return saved_ptr; + +fail: + p->size = saved_size; + return NULL; +} + +guint8* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, guint16 v) { + guint8 *d; + g_assert(p); + + if (!(d = avahi_dns_packet_extend(p, sizeof(guint16)))) + return NULL; + + *((guint16*) d) = g_htons(v); + return d; +} + +guint8 *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, guint32 v) { + guint8 *d; + g_assert(p); + + if (!(d = avahi_dns_packet_extend(p, sizeof(guint32)))) + return NULL; + + *((guint32*) d) = g_htonl(v); + + return d; +} + +guint8 *avahi_dns_packet_append_bytes(AvahiDnsPacket *p, gconstpointer b, guint l) { + guint8* d; + + g_assert(p); + g_assert(b); + g_assert(l); + + if (!(d = avahi_dns_packet_extend(p, l))) + return NULL; + + memcpy(d, b, l); + return d; +} + +guint8* avahi_dns_packet_append_string(AvahiDnsPacket *p, const gchar *s) { + guint8* d; + guint k; + + g_assert(p); + g_assert(s); + + if ((k = strlen(s)) >= 255) + k = 255; + + if (!(d = avahi_dns_packet_extend(p, k+1))) + return NULL; + + *d = (guint8) k; + memcpy(d+1, s, k); + + return d; +} + +guint8 *avahi_dns_packet_extend(AvahiDnsPacket *p, guint l) { + guint8 *d; + + g_assert(p); + + if (p->size+l > p->max_size) + return NULL; + + d = AVAHI_DNS_PACKET_DATA(p) + p->size; + p->size += l; + + return d; +} + +gint avahi_dns_packet_check_valid(AvahiDnsPacket *p) { + guint16 flags; + g_assert(p); + + if (p->size < 12) + return -1; + + flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS); + + if (flags & AVAHI_DNS_FLAG_OPCODE || flags & AVAHI_DNS_FLAG_RCODE) + return -1; + + return 0; +} + +gint avahi_dns_packet_is_query(AvahiDnsPacket *p) { + g_assert(p); + + return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR); +} + +/* Read a label from a DNS packet, escape "\" and ".", append \0 */ +static gchar *escape_label(guint8* src, guint src_length, gchar **ret_name, guint *ret_name_length) { + gchar *r; + + g_assert(src); + g_assert(ret_name); + g_assert(*ret_name); + g_assert(ret_name_length); + g_assert(*ret_name_length > 0); + + r = *ret_name; + + while (src_length > 0) { + if (*src == '.' || *src == '\\') { + if (*ret_name_length < 3) + return NULL; + + *((*ret_name) ++) = '\\'; + (*ret_name_length) --; + } + + if (*ret_name_length < 2) + return NULL; + + *((*ret_name)++) = *src; + (*ret_name_length) --; + + src_length --; + src++; + } + + **ret_name = 0; + + return r; +} + +static gint consume_labels(AvahiDnsPacket *p, guint index, gchar *ret_name, guint l) { + gint ret = 0; + int compressed = 0; + int first_label = 1; + g_assert(p && ret_name && l); + + for (;;) { + guint8 n; + + if (index+1 > p->size) + return -1; + + n = AVAHI_DNS_PACKET_DATA(p)[index]; + + if (!n) { + index++; + if (!compressed) + ret++; + + if (l < 1) + return -1; + *ret_name = 0; + + return ret; + + } else if (n <= 63) { + /* Uncompressed label */ + index++; + if (!compressed) + ret++; + + if (index + n > p->size) + return -1; + + if ((guint) n + 1 > l) + return -1; + + if (!first_label) { + *(ret_name++) = '.'; + l--; + } else + first_label = 0; + + if (!(escape_label(AVAHI_DNS_PACKET_DATA(p) + index, n, &ret_name, &l))) + return -1; + + index += n; + + if (!compressed) + ret += n; + } else if ((n & 0xC0) == 0xC0) { + /* Compressed label */ + + if (index+2 > p->size) + return -1; + + index = ((guint) (AVAHI_DNS_PACKET_DATA(p)[index] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[index+1]; + + if (!compressed) + ret += 2; + + compressed = 1; + } else + return -1; + } +} + +gint avahi_dns_packet_consume_name(AvahiDnsPacket *p, gchar *ret_name, guint l) { + gint r; + + if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0) + return -1; + + p->rindex += r; + return 0; +} + +gint avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, guint16 *ret_v) { + g_assert(p); + g_assert(ret_v); + + if (p->rindex + sizeof(guint16) > p->size) + return -1; + + *ret_v = g_ntohs(*((guint16*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex))); + p->rindex += sizeof(guint16); + + return 0; +} + +gint avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, guint32 *ret_v) { + g_assert(p); + g_assert(ret_v); + + if (p->rindex + sizeof(guint32) > p->size) + return -1; + + *ret_v = g_ntohl(*((guint32*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex))); + p->rindex += sizeof(guint32); + + return 0; +} + +gint avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, gpointer ret_data, guint l) { + g_assert(p); + g_assert(ret_data); + g_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; +} + +gint avahi_dns_packet_consume_string(AvahiDnsPacket *p, gchar *ret_string, guint l) { + guint k; + + g_assert(p); + g_assert(ret_string); + g_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; + +} + +gconstpointer avahi_dns_packet_get_rptr(AvahiDnsPacket *p) { + g_assert(p); + + if (p->rindex > p->size) + return NULL; + + return AVAHI_DNS_PACKET_DATA(p) + p->rindex; +} + +gint avahi_dns_packet_skip(AvahiDnsPacket *p, guint length) { + g_assert(p); + + if (p->rindex + length > p->size) + return -1; + + p->rindex += length; + return 0; +} + +AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, gboolean *ret_cache_flush) { + gchar name[257], buf[257]; + guint16 type, class; + guint32 ttl; + guint16 rdlength; + AvahiRecord *r = NULL; + gconstpointer start; + + g_assert(p); + g_assert(ret_cache_flush); + +/* g_message("consume_record()"); */ + + 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; + +/* g_message("name = %s, rdlength = %u", name, rdlength); */ + + *ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH); + class &= ~AVAHI_DNS_CACHE_FLUSH; + + start = avahi_dns_packet_get_rptr(p); + + r = avahi_record_new_full(name, class, type); + + switch (type) { + case AVAHI_DNS_TYPE_PTR: + case AVAHI_DNS_TYPE_CNAME: + +/* g_message("ptr"); */ + + if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0) + goto fail; + + r->data.ptr.name = g_strdup(buf); + break; + + + case AVAHI_DNS_TYPE_SRV: + +/* g_message("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) + goto fail; + + r->data.srv.name = g_strdup(buf); + break; + + case AVAHI_DNS_TYPE_HINFO: + +/* g_message("hinfo"); */ + + if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0) + goto fail; + + r->data.hinfo.cpu = g_strdup(buf); + + if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0) + goto fail; + + r->data.hinfo.os = g_strdup(buf); + break; + + case AVAHI_DNS_TYPE_TXT: + +/* g_message("txt"); */ + + if (rdlength > 0) { + r->data.txt.string_list = avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength); + + if (avahi_dns_packet_skip(p, rdlength) < 0) + goto fail; + } else + r->data.txt.string_list = NULL; + + break; + + case AVAHI_DNS_TYPE_A: + +/* g_message("A"); */ + + if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0) + goto fail; + + break; + + case AVAHI_DNS_TYPE_AAAA: + +/* g_message("aaaa"); */ + + if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0) + goto fail; + + break; + + default: + +/* g_message("generic"); */ + + if (rdlength > 0) { + + r->data.generic.data = g_memdup(avahi_dns_packet_get_rptr(p), rdlength); + + if (avahi_dns_packet_skip(p, rdlength) < 0) + goto fail; + } + + break; + } + +/* g_message("%i == %u ?", (guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start, rdlength); */ + + /* Check if we read enough data */ + if ((guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start != rdlength) + goto fail; + + r->ttl = ttl; + + return r; + +fail: + if (r) + avahi_record_unref(r); + + return NULL; +} + +AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, gboolean *ret_unicast_response) { + gchar name[256]; + guint16 type, class; + + g_assert(p); + g_assert(ret_unicast_response); + + 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; + + *ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE); + class &= ~AVAHI_DNS_UNICAST_RESPONSE; + + return avahi_key_new(name, class, type); +} + +guint8* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, gboolean unicast_response) { + guint8 *t; + guint size; + + g_assert(p); + g_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->class | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) { + p->size = size; + return NULL; + } + + return t; +} + +guint8* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, gboolean cache_flush) { + guint8 *t, *l, *start; + guint size; + + g_assert(p); + g_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->class | AVAHI_DNS_CACHE_FLUSH) : (r->key->class &~ AVAHI_DNS_CACHE_FLUSH)) || + !avahi_dns_packet_append_uint32(p, r->ttl) || + !(l = avahi_dns_packet_append_uint16(p, 0))) + goto fail; + + start = avahi_dns_packet_extend(p, 0); + + switch (r->key->type) { + + case AVAHI_DNS_TYPE_PTR: + case AVAHI_DNS_TYPE_CNAME : + + if (!(avahi_dns_packet_append_name(p, r->data.ptr.name))) + goto fail; + + 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)) + goto fail; + + 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)) + goto fail; + + break; + + case AVAHI_DNS_TYPE_TXT: { + + guint8 *data; + guint size; + + size = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0); + +/* g_message("appending string: %u %p", size, r->data.txt.string_list); */ + + if (!(data = avahi_dns_packet_extend(p, size))) + goto fail; + + avahi_string_list_serialize(r->data.txt.string_list, data, size); + break; + } + + + case AVAHI_DNS_TYPE_A: + + if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address))) + goto fail; + + break; + + case AVAHI_DNS_TYPE_AAAA: + + if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address))) + goto fail; + + break; + + default: + + if (r->data.generic.size && + avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size)) + goto fail; + + break; + } + + + + + size = avahi_dns_packet_extend(p, 0) - start; + g_assert(size <= 0xFFFF); + +/* g_message("appended %u", size); */ + + * (guint16*) l = g_htons((guint16) size); + + return t; + + +fail: + p->size = size; + return NULL; +} + +gboolean avahi_dns_packet_is_empty(AvahiDnsPacket *p) { + g_assert(p); + + return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE; +} + +guint avahi_dns_packet_space(AvahiDnsPacket *p) { + g_assert(p); + + g_assert(p->size <= p->max_size); + + return p->max_size - p->size; +} |