srv.h File Reference

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

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Functions
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.
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

ast_get_srv()

int ast_get_srv ( struct ast_channel *  chan, char *  host, int  hostlen, int *  port, const char *  service  )

extern

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 260 of file srv.c.

{
    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_debug(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;
}

References ast_autoservice_start(), ast_autoservice_stop(), ast_copy_string(), ast_debug, ast_free, AST_LIST_HEAD_NOLOCK_INIT_VALUE, AST_LIST_REMOVE_HEAD, ast_search_dns(), current, srv_entry::host, srv_entry::list, srv_entry::port, process_weights(), service, and srv_callback().

Referenced by ast_get_ip_or_srv_with_preference().

ast_srv_cleanup()

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 248 of file srv.c.

{
    const char *host;
    unsigned short port;
 
    if (*context) {
        /* We have a context to clean up. */
        while (!(ast_srv_lookup(context, NULL, &host, &port))) {
        }
    }
}

References ast_srv_lookup(), srv_entry::host, NULL, and srv_entry::port.

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

ast_srv_get_nth_record()

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 309 of file srv.c.

{
    int i = 1;
    int res = -1;
    struct srv_entry *entry;
 
    if (record_num < 1 || record_num > context->num_records) {
        return res;
    }
 
    AST_LIST_TRAVERSE(&context->entries, entry, list) {
        if (i == record_num) {
            *host = entry->host;
            *port = entry->port;
            *priority = entry->priority;
            *weight = entry->weight;
            res = 0;
            break;
        }
        ++i;
    }
 
    return res;
}

References AST_LIST_TRAVERSE, srv_entry::host, srv_entry::list, srv_entry::port, priority, srv_entry::priority, weight, and srv_entry::weight.

Referenced by srv_result_read().

ast_srv_get_record_count()

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 304 of file srv.c.

{
    return context->num_records;
}

Referenced by srv_result_read().

ast_srv_lookup()

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

extern

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 202 of file srv.c.

{
    struct srv_entry *cur;
 
    if (*context == NULL) {
        if (!(*context = ast_calloc(1, sizeof(struct srv_context)))) {
            return -1;
        }
        AST_LIST_HEAD_INIT_NOLOCK(&(*context)->entries);
 
        if (((ast_search_dns(*context, service, C_IN, T_SRV, srv_callback)) < 1) ||
            AST_LIST_EMPTY(&(*context)->entries)) {
            ast_free(*context);
            *context = NULL;
            return -1;
        }
 
        if ((*context)->have_weights) {
            process_weights(*context);
        }
 
        (*context)->prev = AST_LIST_FIRST(&(*context)->entries);
        *host = (*context)->prev->host;
        *port = (*context)->prev->port;
        AST_LIST_TRAVERSE(&(*context)->entries, cur, list) {
            ++((*context)->num_records);
        }
        return 0;
    }
 
    if (((*context)->prev = AST_LIST_NEXT((*context)->prev, list))) {
        /* Retrieve next item in result */
        *host = (*context)->prev->host;
        *port = (*context)->prev->port;
        return 0;
    } else {
        /* No more results */
        while ((cur = AST_LIST_REMOVE_HEAD(&(*context)->entries, list))) {
            ast_free(cur);
        }
        ast_free(*context);
        *context = NULL;
        return 1;
    }
}

References ast_calloc, ast_free, AST_LIST_EMPTY, AST_LIST_FIRST, AST_LIST_HEAD_INIT_NOLOCK, AST_LIST_NEXT, AST_LIST_REMOVE_HEAD, AST_LIST_TRAVERSE, ast_search_dns(), srv_entry::host, srv_entry::list, NULL, srv_entry::port, process_weights(), service, and srv_callback().

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