Ability to set DONTFRAGMENT for UDP packets in ext/sockets

Hi all,

I noticed there is currently no way to set the DF (don't fragment) bit for UDP packets sent using ext/sockets. This is problematic when trying to do UDP path MTU discovery using PHP.

I'm unsure if there may be any cross-platform concerns to watch out for here, but I'm just generally curious if there's a reason why there's no support for this, or if just nobody considered to implement it.

Thanks,
Dylan.