ares_set_local_ip6 - Man Page

#include <ares.h>

void ares_set_local_ip6(ares_channel_t *channel, const unsigned char* local_ip6)

The ares_set_local_ip6 function sets the IPv6 address for outbound IPv6 requests.  The parameter local_ip6 is specified in network byte order. This allows users to specify outbound interfaces when used on multi-homed systems.  The local_ip6 argument must be 16 bytes in length.

ares_set_local_ip4(3)

This function was added in c-ares 1.7.4

ares_set_local_dev(3), ares_set_local_ip4(3).