feat: add support for accept and accept4

[haraldh]

Since the socket address of the accepted socket is unknown,
all bytes are set to zero and the length is truncated to the size
of the generic struct sockaddr.

Fixes: #284
Supersedes: #286

Signed-off-by: Harald Hoyer [email protected]

[haraldh]

Side note: while writing test code, I encountered:

In file included from main.c:4:
In file included from wasi-libc/sysroot/include/sys/socket.h:5:
In file included from wasi-libc/sysroot/include/__header_sys_socket.h:5:
wasi-libc/sysroot/include/__struct_sockaddr.h:10:14: error: use of undeclared identifier 'max_align_t'
    _Alignas(max_align_t) sa_family_t sa_family;

I hope, this is just me using wasi-sdk-14.0 mixed with this HEAD branch's sysroot

[npmccallum]

@sunfishcode This is the feature I mentioned on the phone. We should consider this a blocker before starting the wit-bindgen work.

[sunfishcode]

Overall looks good!

When adding new files, such as this accept.c, we should add them in libc-bottom-half/sources, since they aren't derived from cloudlibc. See below for how to resolve the common/errno.h header:

[sunfishcode]

Looks good!

[codefromthecrypt]

I suppose the rationale for validating, but dropping the only flag besides nonblock is because it isn't in wasi, right? https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#fdflags cc @deadprogram who's implementing tinygo tinygo-org/tinygo#2748 🎖️

[codefromthecrypt]

sorry tagged wrong person meant @rvolosatovs 😊

[rvolosatovs]

Yes, this behavior is not relevant for the TinyGo implementation, since this is a wrapper for sock_accept, whereas in the TinyGo PR we call it directly via WASI