Support AIX for get_peer_cred

[ecnelises]

Motivation

We're proposing AIX on PowerPC as Tier-3 target (see rust-lang/compiler-team#553). And we encountered build failure of tokio for AIX.

Solution

Implement AIX's version of get_peer_cred which is almost the same as FreeBSD's. Since AIX hasn't been officially accepted, this is in draft status.

[thegreystone]

Since issue 553, I believe AIX has been accepted as a platform. Does this mean that this PR can leave draft status now?

[Noah-Kennedy]

Is this in stable yet?

[Darksonn]

Can you please clarify the state of this PR?

[ecnelises]

Yes, AIX recognition has been in Rust stable (which means no warnings will be emitted), although some dependent crates are not available yet. This patch has left draft status and is ready to be checked-in after approval.

[Darksonn]

Is it possible to add this platform to our CI setup? We cross-compile to other weird targets in the following CI check:

tokio/.github/workflows/ci.yml

Lines 256 to 278 in e629ad7

	cross-check:
	name: cross-check
	runs-on: ubuntu-latest
	strategy:
	matrix:
	target:
	- powerpc-unknown-linux-gnu
	- powerpc64-unknown-linux-gnu
	- mips-unknown-linux-gnu
	- arm-linux-androideabi
	- mipsel-unknown-linux-musl
	steps:
	- uses: actions/checkout@v3
	- name: Install Rust ${{ env.rust_stable }}
	uses: dtolnay/rust-toolchain@master
	with:
	toolchain: ${{ env.rust_stable }}
	target: ${{ matrix.target }}
	- name: Install cross
	uses: taiki-e/install-action@cross
	- run: cross check --workspace --all-features --target ${{ matrix.target }}
	env:
	RUSTFLAGS: --cfg tokio_unstable -Dwarnings

The cross-test check also runs tests on the platform, but that's not possible for all platforms.

[Darksonn]

Unfortunately, this fails with the following error:

$ rustup toolchain install stable --target powerpc64-ibm-aix --profile minimal --no-self-update
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
info: latest update on 2023-02-09, rust version 1.67.1 (d5a82bbd2 2023-02-07)
error: component 'rust-std' for target 'powerpc64-ibm-aix' is unavailable for download for channel 'stable'
If you don't need the component, you could try a minimal installation with:

    rustup toolchain add stable --profile minimal

Perhaps adding this to CI is not possible today?

[ecnelises]

Ah, I forgot about it. I'll add it back once powerpc64-ibm-aix is available in rustup.

[Darksonn]

Since this cannot be tested on CI today, I am ok with merging it as-is. I would appreciate a CI PR if AIX resources become available in rustup in the future.

Have you executed this code at least once to sanity check it? If so, then I am happy with merging it as-is.

[Darksonn]

Ping regarding my question on whether you have executed this?

[ecnelises]

Hi, sorry for the very late response, this builds successfully on AIX, and the function works as expected on AIX. (I cannot run the whole test suite for tokio now because of some issues met in mio)

[Darksonn]

Thank you for confirming.