c-ares specifying network interface for the DNS re

Question

Is there a way in which you can set the network interface to which the DNS requests can be bound to.

We have a project which requires to use a highpriority streaming session go through one interface and all the other requests channeled through the second one.

example: setting 'eth0' so that all the ares requests will go through 'eth0' and not on 'wlan0'.

I was not able to find any API in c-ares (in ares_init_options() API) that gives this option of setting interface.

Can you please let me know if there is some way to achive this or if I missed something.

Thanks, Arjun

Answer 1

If you have a fairly new c-ares (c-ares >= 1.7.4), check out ares.h (It's the only place I've actually found it referenced).

/* These next 3 configure local binding for the out-going socket
 * connection.  Use these to specify source IP and/or network device
 * on multi-homed systems.
 */
CARES_EXTERN void ares_set_local_ip4(ares_channel channel, unsigned int local_ip);

/* local_ip6 should be 16 bytes in length */
CARES_EXTERN void ares_set_local_ip6(ares_channel channel,
                                     const unsigned char* local_ip6);

/* local_dev_name should be null terminated. */
CARES_EXTERN void ares_set_local_dev(ares_channel channel,
                                     const char* local_dev_name);