diff options
Diffstat (limited to 'pjlib-util/src/pjlib-util/srv_resolver.c')
| -rw-r--r-- | pjlib-util/src/pjlib-util/srv_resolver.c | 674 |
1 files changed, 674 insertions, 0 deletions
diff --git a/pjlib-util/src/pjlib-util/srv_resolver.c b/pjlib-util/src/pjlib-util/srv_resolver.c new file mode 100644 index 0000000..8f133cf --- /dev/null +++ b/pjlib-util/src/pjlib-util/srv_resolver.c @@ -0,0 +1,674 @@ +/* $Id: srv_resolver.c 3553 2011-05-05 06:14:19Z nanang $ */ +/* + * 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) +{ + int 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; + } +} + + |