DNS SRV Record Lookup Support for Asterisk. More...
#include "asterisk.h"
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include "asterisk/channel.h"
#include "asterisk/srv.h"
#include "asterisk/dns.h"
#include "asterisk/utils.h"
#include "asterisk/linkedlists.h"
Go to the source code of this file.
Data Structures | |
struct | srv_context |
struct | srv_context::srv_entries |
struct | srv_entry |
Functions | |
int | ast_get_srv (struct ast_channel *chan, char *host, int hostlen, int *port, const char *service) |
static int | parse_srv (unsigned char *answer, int len, unsigned char *msg, struct srv_entry **result) |
static void | process_weights (struct srv_context *context) |
static int | srv_callback (void *context, unsigned char *answer, int len, unsigned char *fullanswer) |
DNS SRV Record Lookup Support for Asterisk.
Definition in file srv.c.
int ast_get_srv | ( | struct ast_channel * | chan, |
char * | host, | ||
int | hostlen, | ||
int * | port, | ||
const char * | service | ||
) |
Lookup entry in SRV records Returns 1 if found, 0 if not found, -1 on hangup Only do SRV record lookup if you get a domain without a port. If you get a port #, it's a DNS host name.
chan | Ast channel |
host | host name (return value) |
hostlen | Length of string "host" |
port | Port number (return value) |
service | Service tag for SRV lookup (like "_sip._udp" or "_stun._udp" |
Definition at line 200 of file srv.c.
References ast_autoservice_start(), ast_autoservice_stop(), ast_copy_string(), ast_free, AST_LIST_HEAD_NOLOCK_INIT_VALUE, AST_LIST_REMOVE_HEAD, ast_search_dns(), ast_verb, srv_context::entries, srv_context::have_weights, srv_entry::host, srv_entry::port, process_weights(), and srv_callback().
Referenced by ast_get_ip_or_srv(), and create_addr().
{ struct srv_context context = { .entries = AST_LIST_HEAD_NOLOCK_INIT_VALUE }; struct srv_entry *current; int ret; if (chan && ast_autoservice_start(chan) < 0) return -1; ret = ast_search_dns(&context, service, C_IN, T_SRV, srv_callback); if (context.have_weights) process_weights(&context); if (chan) ret |= ast_autoservice_stop(chan); /* TODO: there could be a "." entry in the returned list of answers... if so, this requires special handling */ /* the list of entries will be sorted in the proper selection order already, so we just need the first one (if any) */ if ((ret > 0) && (current = AST_LIST_REMOVE_HEAD(&context.entries, list))) { ast_copy_string(host, current->host, hostlen); *port = current->port; ast_free(current); ast_verb(4, "ast_get_srv: SRV lookup for '%s' mapped to host %s, port %d\n", service, host, *port); } else { host[0] = '\0'; *port = -1; } while ((current = AST_LIST_REMOVE_HEAD(&context.entries, list))) ast_free(current); return ret; }
static int parse_srv | ( | unsigned char * | answer, |
int | len, | ||
unsigned char * | msg, | ||
struct srv_entry ** | result | ||
) | [static] |
Definition at line 70 of file srv.c.
References ast_calloc, ast_log(), srv_entry::host, LOG_WARNING, srv_entry::port, srv_entry::priority, and srv_entry::weight.
Referenced by srv_callback().
{ struct srv { unsigned short priority; unsigned short weight; unsigned short port; } __attribute__((__packed__)) *srv = (struct srv *) answer; int res = 0; char repl[256] = ""; struct srv_entry *entry; if (len < sizeof(*srv)) return -1; answer += sizeof(*srv); len -= sizeof(*srv); if ((res = dn_expand(msg, answer + len, answer, repl, sizeof(repl) - 1)) <= 0) { ast_log(LOG_WARNING, "Failed to expand hostname\n"); return -1; } /* the magic value "." for the target domain means that this service is *NOT* available at the domain we searched */ if (!strcmp(repl, ".")) return -1; if (!(entry = ast_calloc(1, sizeof(*entry) + strlen(repl)))) return -1; entry->priority = ntohs(srv->priority); entry->weight = ntohs(srv->weight); entry->port = ntohs(srv->port); strcpy(entry->host, repl); *result = entry; return 0; }
static void process_weights | ( | struct srv_context * | context | ) | [static] |
Definition at line 148 of file srv.c.
References AST_LIST_APPEND_LIST, AST_LIST_FIRST, AST_LIST_HEAD_NOLOCK_INIT_VALUE, AST_LIST_MOVE_CURRENT, AST_LIST_TRAVERSE, AST_LIST_TRAVERSE_SAFE_BEGIN, AST_LIST_TRAVERSE_SAFE_END, ast_random(), srv_context::entries, srv_entry::priority, srv_entry::weight, and srv_entry::weight_sum.
Referenced by ast_get_srv().
{ struct srv_entry *current; struct srv_entries newlist = AST_LIST_HEAD_NOLOCK_INIT_VALUE; while (AST_LIST_FIRST(&context->entries)) { unsigned int random_weight; unsigned int weight_sum; unsigned short cur_priority = AST_LIST_FIRST(&context->entries)->priority; struct srv_entries temp_list = AST_LIST_HEAD_NOLOCK_INIT_VALUE; weight_sum = 0; AST_LIST_TRAVERSE_SAFE_BEGIN(&context->entries, current, list) { if (current->priority != cur_priority) break; AST_LIST_MOVE_CURRENT(&temp_list, list); } AST_LIST_TRAVERSE_SAFE_END; while (AST_LIST_FIRST(&temp_list)) { weight_sum = 0; AST_LIST_TRAVERSE(&temp_list, current, list) current->weight_sum = weight_sum += current->weight; /* if all the remaining entries have weight == 0, then just append them to the result list and quit */ if (weight_sum == 0) { AST_LIST_APPEND_LIST(&newlist, &temp_list, list); break; } random_weight = 1 + (unsigned int) ((float) weight_sum * (ast_random() / ((float) RAND_MAX + 1.0))); AST_LIST_TRAVERSE_SAFE_BEGIN(&temp_list, current, list) { if (current->weight < random_weight) continue; AST_LIST_MOVE_CURRENT(&newlist, list); break; } AST_LIST_TRAVERSE_SAFE_END; } } /* now that the new list has been ordered, put it in place */ AST_LIST_APPEND_LIST(&context->entries, &newlist, list); }
static int srv_callback | ( | void * | context, |
unsigned char * | answer, | ||
int | len, | ||
unsigned char * | fullanswer | ||
) | [static] |
Definition at line 111 of file srv.c.
References AST_LIST_INSERT_BEFORE_CURRENT, AST_LIST_INSERT_TAIL, AST_LIST_TRAVERSE_SAFE_BEGIN, AST_LIST_TRAVERSE_SAFE_END, srv_context::entries, srv_context::have_weights, parse_srv(), srv_entry::priority, and srv_entry::weight.
Referenced by ast_get_srv().
{ struct srv_context *c = (struct srv_context *) context; struct srv_entry *entry = NULL; struct srv_entry *current; if (parse_srv(answer, len, fullanswer, &entry)) return -1; if (entry->weight) c->have_weights = 1; AST_LIST_TRAVERSE_SAFE_BEGIN(&c->entries, current, list) { /* insert this entry just before the first existing entry with a higher priority */ if (current->priority <= entry->priority) continue; AST_LIST_INSERT_BEFORE_CURRENT(entry, list); entry = NULL; break; } AST_LIST_TRAVERSE_SAFE_END; /* if we didn't find a place to insert the entry before an existing entry, then just add it to the end */ if (entry) AST_LIST_INSERT_TAIL(&c->entries, entry, list); return 0; }