ARES_GET_SERVERS

Section: C Library Functions (3)
Updated: 5 March 2010
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NAME

ares_get_servers, ares_get_servers_ports - Retrieve name servers from an initialized ares_channel

SYNOPSIS

#include <ares.h>

int ares_get_servers(ares_channel channel, struct ares_addr_node **servers)
int ares_get_servers_ports(ares_channel channel, struct ares_addr_port_node **servers)

DESCRIPTION

The ares_get_servers(3) function retrieves name servers configuration from the channel data identified by channel, as a linked list of ares_addr_node structs storing a pointer to the first node at the address specified by servers.

The ares_get_servers_ports(3) function also retrieves any per-server port information that may have been previously configured, returning a linked list of ares_addr_port structures.

Function caller may traverse the returned name server linked list, or may use it directly as suitable input for the ares_set_servers(3) / ares_set_servers_ports(3) functions, but shall not shrink or extend the list on its own.

Each node of the name server linked list is stored in memory dynamically allocated and managed by c-ares. It is the caller's responsibility to free the resulting linked list, using ares_free_data(3) , once the caller does not need it any longer.

This function is capable of handling IPv4 and IPv6 name server addresses simultaneously, rendering ares_save_options(3) with optmask ARES_OPT_SERVERS functionally obsolete except for IPv4-only name server usage.

RETURN VALUES

This function may return any of the following values:

ARES_SUCCESS: The name servers configuration was successfully retrieved
ARES_ENOMEM: The memory was exhausted
ARES_ENODATA: The channel data identified by channel was invalid.

AVAILABILITY

ares_get_servers(3) was added in c-ares 1.7.1; ares_get_servers_ports(3) was added in c-ares 1.11.0.

AUTHOR

Implementation of this function and associated library internals are based on code, comments and feedback provided in November and December of 2008 by Daniel Stenberg, Gregor Jasny, Phil Blundell and Yang Tse, December 2009 by Cedric Bail, February 2010 by Jakub Hrozek. On March 2010 Yang Tse shuffled all the bits and this function popped out.
Copyright 1998 by the Massachusetts Institute of Technology.
Copyright (C) 2008-2010 by Daniel Stenberg