Wed Aug 7 17:16:13 2019

Asterisk developer's documentation


srv.h File Reference

Support for DNS SRV records, used in to locate SIP services. More...

Go to the source code of this file.

Functions

int ast_get_srv (struct ast_channel *chan, char *host, int hostlen, int *port, const char *service)
void ast_srv_cleanup (struct srv_context **context)
 Cleanup resources associated with ast_srv_lookup.
int ast_srv_get_nth_record (struct srv_context *context, int record_num, const char **host, unsigned short *port, unsigned short *priority, unsigned short *weight)
 Retrieve details from a specific SRV record.
unsigned int ast_srv_get_record_count (struct srv_context *context)
 Get the number of records for a given SRV context.
int ast_srv_lookup (struct srv_context **context, const char *service, const char **host, unsigned short *port)
 Retrieve set of SRV lookups, in order.

Detailed Description

Support for DNS SRV records, used in to locate SIP services.

Note:
Note: This SRV record support will respect the priority and weight elements of the records that are returned, but there are no provisions for retrying or failover between records.

Definition in file srv.h.


Function Documentation

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.

Parameters:
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 263 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().

00264 {
00265    struct srv_context context = { .entries = AST_LIST_HEAD_NOLOCK_INIT_VALUE };
00266    struct srv_entry *current;
00267    int ret;
00268 
00269    if (chan && ast_autoservice_start(chan) < 0) {
00270       return -1;
00271    }
00272 
00273    ret = ast_search_dns(&context, service, C_IN, T_SRV, srv_callback);
00274 
00275    if (context.have_weights) {
00276       process_weights(&context);
00277    }
00278 
00279    if (chan) {
00280       ret |= ast_autoservice_stop(chan);
00281    }
00282 
00283    /* TODO: there could be a "." entry in the returned list of
00284       answers... if so, this requires special handling */
00285 
00286    /* the list of entries will be sorted in the proper selection order
00287       already, so we just need the first one (if any) */
00288 
00289    if ((ret > 0) && (current = AST_LIST_REMOVE_HEAD(&context.entries, list))) {
00290       ast_copy_string(host, current->host, hostlen);
00291       *port = current->port;
00292       ast_free(current);
00293       ast_verb(4, "ast_get_srv: SRV lookup for '%s' mapped to host %s, port %d\n",
00294                 service, host, *port);
00295    } else {
00296       host[0] = '\0';
00297       *port = -1;
00298    }
00299 
00300    while ((current = AST_LIST_REMOVE_HEAD(&context.entries, list))) {
00301       ast_free(current);
00302    }
00303 
00304    return ret;
00305 }

void ast_srv_cleanup ( struct srv_context **  context  ) 

Cleanup resources associated with ast_srv_lookup.

Parameters:
context Pointer passed into ast_srv_lookup

Definition at line 251 of file srv.c.

References ast_srv_lookup(), and srv_entry::port.

Referenced by launch_ha_netscript(), srds_destroy_cb(), and srv_datastore_setup().

00252 {
00253    const char *host;
00254    unsigned short port;
00255 
00256    if (*context) {
00257       /* We have a context to clean up. */
00258       while (!(ast_srv_lookup(context, NULL, &host, &port))) {
00259       }
00260    }
00261 }

int ast_srv_get_nth_record ( struct srv_context context,
int  record_num,
const char **  host,
unsigned short *  port,
unsigned short *  priority,
unsigned short *  weight 
)

Retrieve details from a specific SRV record.

After calling ast_srv_lookup, the srv_context will contain the data from several records. You can retrieve the data of a specific one by asking for a specific record number. The records are sorted based on priority and secondarily based on weight. See RFC 2782 for the exact sorting rules.

Parameters:
context The context returned by ast_srv_lookup
record_num The 1-indexed record number to retrieve
[out] host The host portion of the record
[out] port The port portion of the record
[out] priority The priority portion of the record
[out] weight The weight portion of the record
Return values:
-1 Failed to retrieve information. Likely due to an out of range record_num
0 Success

Definition at line 312 of file srv.c.

References AST_LIST_TRAVERSE, srv_context::entries, srv_entry::host, srv_context::num_records, srv_entry::port, srv_entry::priority, and srv_entry::weight.

Referenced by srv_result_read().

00314 {
00315    int i = 1;
00316    int res = -1;
00317    struct srv_entry *entry;
00318 
00319    if (record_num < 1 || record_num > context->num_records) {
00320       return res;
00321    }
00322 
00323    AST_LIST_TRAVERSE(&context->entries, entry, list) {
00324       if (i == record_num) {
00325          *host = entry->host;
00326          *port = entry->port;
00327          *priority = entry->priority;
00328          *weight = entry->weight;
00329          res = 0;
00330          break;
00331       }
00332       ++i;
00333    }
00334 
00335    return res;
00336 }

unsigned int ast_srv_get_record_count ( struct srv_context context  ) 

Get the number of records for a given SRV context.

This is meant to be used after calling ast_srv_lookup, so that one may retrieve the number of records returned during a specific SRV lookup.

Parameters:
context The context returned by ast_srv_lookup
Returns:
Number of records in context

Definition at line 307 of file srv.c.

References srv_context::num_records.

Referenced by srv_result_read().

00308 {
00309    return context->num_records;
00310 }

int ast_srv_lookup ( struct srv_context **  context,
const char *  service,
const char **  host,
unsigned short *  port 
)

Retrieve set of SRV lookups, in order.

Parameters:
[in] context A pointer in which to hold the result
[in] service The service name to look up
[out] host Result host
[out] port Associated TCP portnum
Return values:
-1 Query failed
0 Result exists in host and port
1 No more results

Definition at line 206 of file srv.c.

References ast_calloc, ast_free, AST_LIST_FIRST, AST_LIST_HEAD_INIT_NOLOCK, AST_LIST_NEXT, AST_LIST_REMOVE_HEAD, AST_LIST_TRAVERSE, ast_search_dns(), process_weights(), and srv_callback().

Referenced by ast_srv_cleanup(), launch_ha_netscript(), and srv_datastore_setup().

00207 {
00208    struct srv_entry *cur;
00209 
00210    if (*context == NULL) {
00211       if (!(*context = ast_calloc(1, sizeof(struct srv_context)))) {
00212          return -1;
00213       }
00214       AST_LIST_HEAD_INIT_NOLOCK(&(*context)->entries);
00215 
00216       if ((ast_search_dns(*context, service, C_IN, T_SRV, srv_callback)) < 0) {
00217          ast_free(*context);
00218          *context = NULL;
00219          return -1;
00220       }
00221 
00222       if ((*context)->have_weights) {
00223          process_weights(*context);
00224       }
00225 
00226       (*context)->prev = AST_LIST_FIRST(&(*context)->entries);
00227       *host = (*context)->prev->host;
00228       *port = (*context)->prev->port;
00229       AST_LIST_TRAVERSE(&(*context)->entries, cur, list) {
00230          ++((*context)->num_records);
00231       }
00232       return 0;
00233    }
00234 
00235    if (((*context)->prev = AST_LIST_NEXT((*context)->prev, list))) {
00236       /* Retrieve next item in result */
00237       *host = (*context)->prev->host;
00238       *port = (*context)->prev->port;
00239       return 0;
00240    } else {
00241       /* No more results */
00242       while ((cur = AST_LIST_REMOVE_HEAD(&(*context)->entries, list))) {
00243          ast_free(cur);
00244       }
00245       ast_free(*context);
00246       *context = NULL;
00247       return 1;
00248    }
00249 }


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