| /* $Id$ */ |
| /* |
| * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com) |
| * Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org> |
| * |
| * 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; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| */ |
| #include <pjlib-util/srv_resolver.h> |
| #include <pjlib-util/errno.h> |
| #include <pj/array.h> |
| #include <pj/assert.h> |
| #include <pj/log.h> |
| #include <pj/os.h> |
| #include <pj/pool.h> |
| #include <pj/rand.h> |
| #include <pj/string.h> |
| |
| |
| #define THIS_FILE "srv_resolver.c" |
| |
| #define ADDR_MAX_COUNT PJ_DNS_MAX_IP_IN_A_REC |
| |
| struct common |
| { |
| pj_dns_type type; /**< Type of this structure.*/ |
| }; |
| |
| struct srv_target |
| { |
| struct common common; |
| pj_dns_srv_async_query *parent; |
| pj_str_t target_name; |
| pj_dns_async_query *q_a; |
| char target_buf[PJ_MAX_HOSTNAME]; |
| pj_str_t cname; |
| char cname_buf[PJ_MAX_HOSTNAME]; |
| unsigned port; |
| unsigned priority; |
| unsigned weight; |
| unsigned sum; |
| unsigned addr_cnt; |
| pj_in_addr addr[ADDR_MAX_COUNT]; |
| }; |
| |
| struct pj_dns_srv_async_query |
| { |
| struct common common; |
| char *objname; |
| |
| pj_dns_type dns_state; /**< DNS type being resolved. */ |
| pj_dns_resolver *resolver; /**< Resolver SIP instance. */ |
| void *token; |
| pj_dns_async_query *q_srv; |
| pj_dns_srv_resolver_cb *cb; |
| pj_status_t last_error; |
| |
| /* Original request: */ |
| unsigned option; |
| pj_str_t full_name; |
| pj_str_t domain_part; |
| pj_uint16_t def_port; |
| |
| /* SRV records and their resolved IP addresses: */ |
| unsigned srv_cnt; |
| struct srv_target srv[PJ_DNS_SRV_MAX_ADDR]; |
| |
| /* Number of hosts in SRV records that the IP address has been resolved */ |
| unsigned host_resolved; |
| |
| }; |
| |
| |
| /* Async resolver callback, forward decl. */ |
| static void dns_callback(void *user_data, |
| pj_status_t status, |
| pj_dns_parsed_packet *pkt); |
| |
| |
| |
| /* |
| * The public API to invoke DNS SRV resolution. |
| */ |
| PJ_DEF(pj_status_t) pj_dns_srv_resolve( const pj_str_t *domain_name, |
| const pj_str_t *res_name, |
| unsigned def_port, |
| pj_pool_t *pool, |
| pj_dns_resolver *resolver, |
| unsigned option, |
| void *token, |
| pj_dns_srv_resolver_cb *cb, |
| pj_dns_srv_async_query **p_query) |
| { |
| pj_size_t len; |
| pj_str_t target_name; |
| pj_dns_srv_async_query *query_job; |
| pj_status_t status; |
| |
| PJ_ASSERT_RETURN(domain_name && domain_name->slen && |
| res_name && res_name->slen && |
| pool && resolver && cb, PJ_EINVAL); |
| |
| /* Build full name */ |
| len = domain_name->slen + res_name->slen + 2; |
| target_name.ptr = (char*) pj_pool_alloc(pool, len); |
| pj_strcpy(&target_name, res_name); |
| if (res_name->ptr[res_name->slen-1] != '.') |
| pj_strcat2(&target_name, "."); |
| len = target_name.slen; |
| pj_strcat(&target_name, domain_name); |
| target_name.ptr[target_name.slen] = '\0'; |
| |
| |
| /* Build the query_job state */ |
| query_job = PJ_POOL_ZALLOC_T(pool, pj_dns_srv_async_query); |
| query_job->common.type = PJ_DNS_TYPE_SRV; |
| query_job->objname = target_name.ptr; |
| query_job->resolver = resolver; |
| query_job->token = token; |
| query_job->cb = cb; |
| query_job->option = option; |
| query_job->full_name = target_name; |
| query_job->domain_part.ptr = target_name.ptr + len; |
| query_job->domain_part.slen = target_name.slen - len; |
| query_job->def_port = (pj_uint16_t)def_port; |
| |
| /* Start the asynchronous query_job */ |
| |
| query_job->dns_state = PJ_DNS_TYPE_SRV; |
| |
| PJ_LOG(5, (query_job->objname, |
| "Starting async DNS %s query_job: target=%.*s:%d", |
| pj_dns_get_type_name(query_job->dns_state), |
| (int)target_name.slen, target_name.ptr, |
| def_port)); |
| |
| status = pj_dns_resolver_start_query(resolver, &target_name, |
| query_job->dns_state, 0, |
| &dns_callback, |
| query_job, &query_job->q_srv); |
| if (status==PJ_SUCCESS && p_query) |
| *p_query = query_job; |
| |
| return status; |
| } |
| |
| |
| /* |
| * Cancel pending query. |
| */ |
| PJ_DEF(pj_status_t) pj_dns_srv_cancel_query(pj_dns_srv_async_query *query, |
| pj_bool_t notify) |
| { |
| pj_bool_t has_pending = PJ_FALSE; |
| unsigned i; |
| |
| if (query->q_srv) { |
| pj_dns_resolver_cancel_query(query->q_srv, PJ_FALSE); |
| query->q_srv = NULL; |
| has_pending = PJ_TRUE; |
| } |
| |
| for (i=0; i<query->srv_cnt; ++i) { |
| struct srv_target *srv = &query->srv[i]; |
| if (srv->q_a) { |
| pj_dns_resolver_cancel_query(srv->q_a, PJ_FALSE); |
| srv->q_a = NULL; |
| has_pending = PJ_TRUE; |
| } |
| } |
| |
| if (has_pending && notify && query->cb) { |
| (*query->cb)(query->token, PJ_ECANCELLED, NULL); |
| } |
| |
| return has_pending? PJ_SUCCESS : PJ_EINVALIDOP; |
| } |
| |
| |
| #define SWAP(type,ptr1,ptr2) if (ptr1 != ptr2) { \ |
| type tmp; \ |
| pj_memcpy(&tmp, ptr1, sizeof(type)); \ |
| pj_memcpy(ptr1, ptr2, sizeof(type)); \ |
| (ptr1)->target_name.ptr = (ptr1)->target_buf;\ |
| pj_memcpy(ptr2, &tmp, sizeof(type)); \ |
| (ptr2)->target_name.ptr = (ptr2)->target_buf;\ |
| } else {} |
| |
| |
| /* Build server entries in the query_job based on received SRV response */ |
| static void build_server_entries(pj_dns_srv_async_query *query_job, |
| pj_dns_parsed_packet *response) |
| { |
| unsigned i; |
| |
| /* Save the Resource Records in DNS answer into SRV targets. */ |
| query_job->srv_cnt = 0; |
| for (i=0; i<response->hdr.anscount && |
| query_job->srv_cnt < PJ_DNS_SRV_MAX_ADDR; ++i) |
| { |
| pj_dns_parsed_rr *rr = &response->ans[i]; |
| struct srv_target *srv = &query_job->srv[query_job->srv_cnt]; |
| |
| if (rr->type != PJ_DNS_TYPE_SRV) { |
| PJ_LOG(4,(query_job->objname, |
| "Received non SRV answer for SRV query_job!")); |
| continue; |
| } |
| |
| if (rr->rdata.srv.target.slen > PJ_MAX_HOSTNAME) { |
| PJ_LOG(4,(query_job->objname, "Hostname is too long!")); |
| continue; |
| } |
| |
| /* Build the SRV entry for RR */ |
| pj_bzero(srv, sizeof(*srv)); |
| srv->target_name.ptr = srv->target_buf; |
| pj_strncpy(&srv->target_name, &rr->rdata.srv.target, |
| sizeof(srv->target_buf)); |
| srv->port = rr->rdata.srv.port; |
| srv->priority = rr->rdata.srv.prio; |
| srv->weight = rr->rdata.srv.weight; |
| |
| ++query_job->srv_cnt; |
| } |
| |
| if (query_job->srv_cnt == 0) { |
| PJ_LOG(4,(query_job->objname, |
| "Could not find SRV record in DNS answer!")); |
| return; |
| } |
| |
| /* First pass: |
| * order the entries based on priority. |
| */ |
| for (i=0; i<query_job->srv_cnt-1; ++i) { |
| unsigned min = i, j; |
| for (j=i+1; j<query_job->srv_cnt; ++j) { |
| if (query_job->srv[j].priority < query_job->srv[min].priority) |
| min = j; |
| } |
| SWAP(struct srv_target, &query_job->srv[i], &query_job->srv[min]); |
| } |
| |
| /* Second pass: |
| * pick one host among hosts with the same priority, according |
| * to its weight. The idea is when one server fails, client should |
| * contact the next server with higher priority rather than contacting |
| * server with the same priority as the failed one. |
| * |
| * The algorithm for selecting server among servers with the same |
| * priority is described in RFC 2782. |
| */ |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| unsigned j, count=1, sum; |
| |
| /* Calculate running sum for servers with the same priority */ |
| sum = query_job->srv[i].sum = query_job->srv[i].weight; |
| for (j=i+1; j<query_job->srv_cnt && |
| query_job->srv[j].priority == query_job->srv[i].priority; ++j) |
| { |
| sum += query_job->srv[j].weight; |
| query_job->srv[j].sum = sum; |
| ++count; |
| } |
| |
| if (count > 1) { |
| unsigned r; |
| |
| /* Elect one random number between zero and the total sum of |
| * weight (inclusive). |
| */ |
| r = pj_rand() % (sum + 1); |
| |
| /* Select the first server which running sum is greater than or |
| * equal to the random number. |
| */ |
| for (j=i; j<i+count; ++j) { |
| if (query_job->srv[j].sum >= r) |
| break; |
| } |
| |
| /* Must have selected one! */ |
| pj_assert(j != i+count); |
| |
| /* Put this entry in front (of entries with same priority) */ |
| SWAP(struct srv_target, &query_job->srv[i], &query_job->srv[j]); |
| |
| /* Remove all other entries (of the same priority) */ |
| while (count > 1) { |
| pj_array_erase(query_job->srv, sizeof(struct srv_target), |
| query_job->srv_cnt, i+1); |
| --count; |
| --query_job->srv_cnt; |
| } |
| } |
| } |
| |
| /* Since we've been moving around SRV entries, update the pointers |
| * in target_name. |
| */ |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| query_job->srv[i].target_name.ptr = query_job->srv[i].target_buf; |
| } |
| |
| /* Check for Additional Info section if A records are available, and |
| * fill in the IP address (so that we won't need to resolve the A |
| * record with another DNS query_job). |
| */ |
| for (i=0; i<response->hdr.arcount; ++i) { |
| pj_dns_parsed_rr *rr = &response->arr[i]; |
| unsigned j; |
| |
| if (rr->type != PJ_DNS_TYPE_A) |
| continue; |
| |
| /* Yippeaiyee!! There is an "A" record! |
| * Update the IP address of the corresponding SRV record. |
| */ |
| for (j=0; j<query_job->srv_cnt; ++j) { |
| if (pj_stricmp(&rr->name, &query_job->srv[j].target_name)==0) { |
| unsigned cnt = query_job->srv[j].addr_cnt; |
| query_job->srv[j].addr[cnt].s_addr = rr->rdata.a.ip_addr.s_addr; |
| /* Only increment host_resolved once per SRV record */ |
| if (query_job->srv[j].addr_cnt == 0) |
| ++query_job->host_resolved; |
| ++query_job->srv[j].addr_cnt; |
| break; |
| } |
| } |
| |
| /* Not valid message; SRV entry might have been deleted in |
| * server selection process. |
| */ |
| /* |
| if (j == query_job->srv_cnt) { |
| PJ_LOG(4,(query_job->objname, |
| "Received DNS SRV answer with A record, but " |
| "couldn't find matching name (name=%.*s)", |
| (int)rr->name.slen, |
| rr->name.ptr)); |
| } |
| */ |
| } |
| |
| /* Rescan again the name specified in the SRV record to see if IP |
| * address is specified as the target name (unlikely, but well, who |
| * knows..). |
| */ |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| pj_in_addr addr; |
| |
| if (query_job->srv[i].addr_cnt != 0) { |
| /* IP address already resolved */ |
| continue; |
| } |
| |
| if (pj_inet_aton(&query_job->srv[i].target_name, &addr) != 0) { |
| query_job->srv[i].addr[query_job->srv[i].addr_cnt++] = addr; |
| ++query_job->host_resolved; |
| } |
| } |
| |
| /* Print resolved entries to the log */ |
| PJ_LOG(5,(query_job->objname, |
| "SRV query_job for %.*s completed, " |
| "%d of %d total entries selected%c", |
| (int)query_job->full_name.slen, |
| query_job->full_name.ptr, |
| query_job->srv_cnt, |
| response->hdr.anscount, |
| (query_job->srv_cnt ? ':' : ' '))); |
| |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| const char *addr; |
| |
| if (query_job->srv[i].addr_cnt != 0) |
| addr = pj_inet_ntoa(query_job->srv[i].addr[0]); |
| else |
| addr = "-"; |
| |
| PJ_LOG(5,(query_job->objname, |
| " %d: SRV %d %d %d %.*s (%s)", |
| i, query_job->srv[i].priority, |
| query_job->srv[i].weight, |
| query_job->srv[i].port, |
| (int)query_job->srv[i].target_name.slen, |
| query_job->srv[i].target_name.ptr, |
| addr)); |
| } |
| } |
| |
| |
| /* Start DNS A record queries for all SRV records in the query_job structure */ |
| static pj_status_t resolve_hostnames(pj_dns_srv_async_query *query_job) |
| { |
| unsigned i; |
| pj_status_t err=PJ_SUCCESS, status; |
| |
| query_job->dns_state = PJ_DNS_TYPE_A; |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| struct srv_target *srv = &query_job->srv[i]; |
| |
| PJ_LOG(5, (query_job->objname, |
| "Starting async DNS A query_job for %.*s", |
| (int)srv->target_name.slen, |
| srv->target_name.ptr)); |
| |
| srv->common.type = PJ_DNS_TYPE_A; |
| srv->parent = query_job; |
| |
| status = pj_dns_resolver_start_query(query_job->resolver, |
| &srv->target_name, |
| PJ_DNS_TYPE_A, 0, |
| &dns_callback, |
| srv, &srv->q_a); |
| if (status != PJ_SUCCESS) { |
| query_job->host_resolved++; |
| err = status; |
| } |
| } |
| |
| return (query_job->host_resolved == query_job->srv_cnt) ? err : PJ_SUCCESS; |
| } |
| |
| /* |
| * This callback is called by PJLIB-UTIL DNS resolver when asynchronous |
| * query_job has completed (successfully or with error). |
| */ |
| static void dns_callback(void *user_data, |
| pj_status_t status, |
| pj_dns_parsed_packet *pkt) |
| { |
| struct common *common = (struct common*) user_data; |
| pj_dns_srv_async_query *query_job; |
| struct srv_target *srv = NULL; |
| unsigned i; |
| |
| if (common->type == PJ_DNS_TYPE_SRV) { |
| query_job = (pj_dns_srv_async_query*) common; |
| srv = NULL; |
| } else if (common->type == PJ_DNS_TYPE_A) { |
| srv = (struct srv_target*) common; |
| query_job = srv->parent; |
| } else { |
| pj_assert(!"Unexpected user data!"); |
| return; |
| } |
| |
| /* Proceed to next stage */ |
| if (query_job->dns_state == PJ_DNS_TYPE_SRV) { |
| |
| /* We are getting SRV response */ |
| |
| query_job->q_srv = NULL; |
| |
| if (status == PJ_SUCCESS && pkt->hdr.anscount != 0) { |
| /* Got SRV response, build server entry. If A records are available |
| * in additional records section of the DNS response, save them too. |
| */ |
| build_server_entries(query_job, pkt); |
| |
| } else if (status != PJ_SUCCESS) { |
| char errmsg[PJ_ERR_MSG_SIZE]; |
| |
| /* Update query_job last error */ |
| query_job->last_error = status; |
| |
| pj_strerror(status, errmsg, sizeof(errmsg)); |
| PJ_LOG(4,(query_job->objname, |
| "DNS SRV resolution failed for %.*s: %s", |
| (int)query_job->full_name.slen, |
| query_job->full_name.ptr, |
| errmsg)); |
| |
| /* Trigger error when fallback is disabled */ |
| if ((query_job->option & |
| (PJ_DNS_SRV_FALLBACK_A | PJ_DNS_SRV_FALLBACK_AAAA)) == 0) |
| { |
| goto on_error; |
| } |
| } |
| |
| /* If we can't build SRV record, assume the original target is |
| * an A record and resolve with DNS A resolution. |
| */ |
| if (query_job->srv_cnt == 0) { |
| /* Looks like we aren't getting any SRV responses. |
| * Resolve the original target as A record by creating a |
| * single "dummy" srv record and start the hostname resolution. |
| */ |
| PJ_LOG(4, (query_job->objname, |
| "DNS SRV resolution failed for %.*s, trying " |
| "resolving A record for %.*s", |
| (int)query_job->full_name.slen, |
| query_job->full_name.ptr, |
| (int)query_job->domain_part.slen, |
| query_job->domain_part.ptr)); |
| |
| /* Create a "dummy" srv record using the original target */ |
| i = query_job->srv_cnt++; |
| pj_bzero(&query_job->srv[i], sizeof(query_job->srv[i])); |
| query_job->srv[i].target_name = query_job->domain_part; |
| query_job->srv[i].priority = 0; |
| query_job->srv[i].weight = 0; |
| query_job->srv[i].port = query_job->def_port; |
| } |
| |
| |
| /* Resolve server hostnames (DNS A record) for hosts which don't have |
| * A record yet. |
| */ |
| if (query_job->host_resolved != query_job->srv_cnt) { |
| status = resolve_hostnames(query_job); |
| if (status != PJ_SUCCESS) |
| goto on_error; |
| |
| /* Must return now. Callback may have been called and query_job |
| * may have been destroyed. |
| */ |
| return; |
| } |
| |
| } else if (query_job->dns_state == PJ_DNS_TYPE_A) { |
| |
| /* Clear the outstanding job */ |
| srv->q_a = NULL; |
| |
| /* Check that we really have answer */ |
| if (status==PJ_SUCCESS && pkt->hdr.anscount != 0) { |
| pj_dns_a_record rec; |
| |
| /* Parse response */ |
| status = pj_dns_parse_a_response(pkt, &rec); |
| if (status != PJ_SUCCESS) |
| goto on_error; |
| |
| pj_assert(rec.addr_count != 0); |
| |
| /* Update CNAME alias, if present. */ |
| if (rec.alias.slen) { |
| pj_assert(rec.alias.slen <= (int)sizeof(srv->cname_buf)); |
| srv->cname.ptr = srv->cname_buf; |
| pj_strcpy(&srv->cname, &rec.alias); |
| } else { |
| srv->cname.slen = 0; |
| } |
| |
| /* Update IP address of the corresponding hostname or CNAME */ |
| if (srv->addr_cnt < ADDR_MAX_COUNT) { |
| srv->addr[srv->addr_cnt++].s_addr = rec.addr[0].s_addr; |
| |
| PJ_LOG(5,(query_job->objname, |
| "DNS A for %.*s: %s", |
| (int)srv->target_name.slen, |
| srv->target_name.ptr, |
| pj_inet_ntoa(rec.addr[0]))); |
| } |
| |
| /* Check for multiple IP addresses */ |
| for (i=1; i<rec.addr_count && srv->addr_cnt < ADDR_MAX_COUNT; ++i) |
| { |
| srv->addr[srv->addr_cnt++].s_addr = rec.addr[i].s_addr; |
| |
| PJ_LOG(5,(query_job->objname, |
| "Additional DNS A for %.*s: %s", |
| (int)srv->target_name.slen, |
| srv->target_name.ptr, |
| pj_inet_ntoa(rec.addr[i]))); |
| } |
| |
| } else if (status != PJ_SUCCESS) { |
| char errmsg[PJ_ERR_MSG_SIZE]; |
| |
| /* Update last error */ |
| query_job->last_error = status; |
| |
| /* Log error */ |
| pj_strerror(status, errmsg, sizeof(errmsg)); |
| PJ_LOG(4,(query_job->objname, "DNS A record resolution failed: %s", |
| errmsg)); |
| } |
| |
| ++query_job->host_resolved; |
| |
| } else { |
| pj_assert(!"Unexpected state!"); |
| query_job->last_error = status = PJ_EINVALIDOP; |
| goto on_error; |
| } |
| |
| /* Check if all hosts have been resolved */ |
| if (query_job->host_resolved == query_job->srv_cnt) { |
| /* Got all answers, build server addresses */ |
| pj_dns_srv_record srv_rec; |
| |
| srv_rec.count = 0; |
| for (i=0; i<query_job->srv_cnt; ++i) { |
| unsigned j; |
| struct srv_target *srv = &query_job->srv[i]; |
| |
| srv_rec.entry[srv_rec.count].priority = srv->priority; |
| srv_rec.entry[srv_rec.count].weight = srv->weight; |
| srv_rec.entry[srv_rec.count].port = (pj_uint16_t)srv->port ; |
| |
| srv_rec.entry[srv_rec.count].server.name = srv->target_name; |
| srv_rec.entry[srv_rec.count].server.alias = srv->cname; |
| srv_rec.entry[srv_rec.count].server.addr_count = 0; |
| |
| pj_assert(srv->addr_cnt <= PJ_DNS_MAX_IP_IN_A_REC); |
| |
| for (j=0; j<srv->addr_cnt; ++j) { |
| srv_rec.entry[srv_rec.count].server.addr[j].s_addr = |
| srv->addr[j].s_addr; |
| ++srv_rec.entry[srv_rec.count].server.addr_count; |
| } |
| |
| if (srv->addr_cnt > 0) { |
| ++srv_rec.count; |
| if (srv_rec.count == PJ_DNS_SRV_MAX_ADDR) |
| break; |
| } |
| } |
| |
| PJ_LOG(5,(query_job->objname, |
| "Server resolution complete, %d server entry(s) found", |
| srv_rec.count)); |
| |
| |
| if (srv_rec.count > 0) |
| status = PJ_SUCCESS; |
| else { |
| status = query_job->last_error; |
| if (status == PJ_SUCCESS) |
| status = PJLIB_UTIL_EDNSNOANSWERREC; |
| } |
| |
| /* Call the callback */ |
| (*query_job->cb)(query_job->token, status, &srv_rec); |
| } |
| |
| |
| return; |
| |
| on_error: |
| /* Check for failure */ |
| if (status != PJ_SUCCESS) { |
| char errmsg[PJ_ERR_MSG_SIZE]; |
| PJ_UNUSED_ARG(errmsg); |
| PJ_LOG(4,(query_job->objname, |
| "DNS %s record resolution error for '%.*s'." |
| " Err=%d (%s)", |
| pj_dns_get_type_name(query_job->dns_state), |
| (int)query_job->domain_part.slen, |
| query_job->domain_part.ptr, |
| status, |
| pj_strerror(status,errmsg,sizeof(errmsg)).ptr)); |
| (*query_job->cb)(query_job->token, status, NULL); |
| return; |
| } |
| } |
| |
| |