ARES_SET_LOCAL_DEV(3)  FreeBSD Library Functions Manual  ARES_SET_LOCAL_DEV(3)

NAME
       ares_set_local_dev - Bind to a specific network device when creating
       sockets.

SYNOPSIS
       #include <ares.h>

       void ares_set_local_dev(ares_channel channel, const char* local_dev_name)

DESCRIPTION
       The ares_set_local_dev function causes all future sockets to be bound
       to this device with SO_BINDTODEVICE.  This forces communications to go
       over a certain interface, which can be useful on multi-homed machines.
       This option is only supported on Linux, and root privileges are
       required for the option to work.  If SO_BINDTODEVICE is not supported
       or the setsocktop call fails (probably because of permissions), the
       error is silently ignored.

SEE ALSO
       ares_set_local_ip4(3) ares_set_local_ip6(3)

NOTES
       This function was added in c-ares 1.7.4

AUTHOR
       Ben Greear

                                 30 June 2010            ARES_SET_LOCAL_DEV(3)