ares_set_local_dev() works without root On Debian GNU/Linux and Alpine GNU/Linux

[kop316]

On https://c-ares.haxx.se/ares_set_local_dev.html

ares_set_local_dev() says it needs root for this function to work, based on the code here:

c-ares/src/lib/ares_process.c

Line 1007 in 809d5e8

/* Only root can do this, and usually not fatal if it doesn't work, so */

#ifdef SO_BINDTODEVICE
          if (channel->local_dev_name[0]) {    
            if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE,
                           channel->local_dev_name, sizeof(channel->local_dev_name))) {
              /* Only root can do this, and usually not fatal if it doesn't work, so */
              /* just continue on. */
            }
          }
#endif

However, SO_BINDTODEVICE works without needing root on at least Debian GNU/Linux and Alpine GNU/Linux. I suspect the same is true on other GNU/Linux distros as well.

I use ares_set_local_dev() here: https://gitlab.com/kop316/mmsd/-/blob/master/src/service.c#L1287

and SO_BINDTODEVICE here: https://gitlab.com/kop316/mmsd/-/blob/master/src/service.c#L3100

Both without root successfully. I suggest changing the documentation to reflect that root is not needed.