Fix recvmsg msghdr outputs - #27399
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recvmsg was writing iovecs after the first at incorrect offsets, and was not updating msg_namelen, msg_controllen or msg_flags in the caller's struct msghdr.
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This implements `recvmmsg` and `sendmmsg`, which were previously `ENOSYS` stubs. Per review feedback, the implementations now live in musl's `sendmmsg.c` and `recvmmsg.c` rather than the syscall stubs: `sendmmsg.c` already contained the emulation loop (previously gated behind `LONG_MAX > INT_MAX`), which is now also enabled under `__EMSCRIPTEN__`, and `recvmmsg.c` gains an equivalent `recvmsg` loop supporting `MSG_WAITFORONE` (timeouts report `ENOSYS`). Since nothing references the syscalls anymore, the `__syscall_recvmmsg`/`__syscall_sendmmsg` surface is removed entirely: the `UNIMPLEMENTED` stubs, the `SYS_` mappings in `arch/emscripten/bits/syscall.h`, the declarations in `emscripten/syscalls.h`, and their `native_sigs.py` entries. The `recvmsg` msghdr output fixes previously bundled here were split out into #27399. Adds `sockets.test_noderawsockets_mmsg` batching two datagrams out via `sendmmsg` and receiving them back in a single `recvmmsg` call. _Made with AI assistance under my review_
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This fixes three issues in the
recvmsgsyscall implementation for sockets, split out separately from #27395 per review feedback.The bugs:
HEAPU8.set(buf, iovbase + bytesRead)skipped ahead by the bytes already read into previous iovecs, corrupting all iovecs after the first.msg_namelenwas not updated to reflect the actual source address size.msg_controllenandmsg_flagswere left untouched rather than zeroed, leaving callers reading uninitialized values as control data / flags.Adds
sockets.test_noderawsockets_udp_recvmsgcovering a datagram scattered across two iovecs along with the msghdr output fields, verified failing before the fix.Made with AI assistance under my review