Export UDP socket option consts on Android

[hulthe]

Description

Export constants for all UDP-specific socket options on Android.
These are already exposed on Linux proper here and here.

Sources

linux/include/uapi/linux/udp.h

bionic/libc/kernel/uapi/linux/udp.h

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

@rustbot label +stable-nominated

[rustbot]

Some changes occurred in the Android module

cc @maurer

[hulthe]

We only need the UDP_SEGMENT and UDP_GRO for our use-case.
But thinking about it... Shouldn't I just add all the socket options in linux/include/uapi/linux/udp.h?

[maurer]

The two you've added are fine. If you want to add more, please restrict yourself to those in https://cs.android.com/android/platform/superproject/main/+/main:bionic/libc/kernel/uapi/linux/udp.h - mostly that means no UDP_ENCAP_OVPNINUDP.

(This is libc, so it's bionic bindings, not Linux kernel bindings. When a constant is supported in Android it'll make its way into the bionic uapi generated headers.)

[hulthe]

@maurer Thanks for clarifying, I was not aware of the distinction with bionic.

I've updated the PR to include all UDP socket options. I've left out the ENCAP-stuff though since I am unfamiliar with them.

I've also added bionic to the list of sources.