Add AF_UNIX sockets implementation (#11681)

* components/dfs: support unix socket nodes

AF_UNIX pathname binding and descriptor passing require DFSv2 socket
nodes and retained open file descriptions across fd tables.

Add socket-node creation for tmpfs and devtmpfs, fd reference helpers,
and socket F_SETFL forwarding.

Impact: DFSv2 socket nodes and descriptor reference handling.
Validation: git diff --cached --check.

* components/net/sal: support local protocol providers

Local IPC protocol families do not have a backing network device.
Store the selected provider in each SAL socket and add a local provider
registry while preserving netdev checks for Internet sockets.

Handle DFSv2 close semantics, socketpair flags, and MSG_CTRUNC for
AF_UNIX integration.

Impact: SAL protocol dispatch for all socket families.
Validation: git diff --cached --check.

* components/lwp: support unix socket messages

Musl AF_UNIX addresses and ancillary data require explicit ABI and
user-memory conversion at the LWP syscall boundary.

Add the musl msghdr layout, bounded address and message copying,
control-message level conversion, and MSG_CTRUNC translation. Correct
receive buffer allocation and copy lengths while handling messages.

Impact: LWP socket syscalls when SAL is enabled.
Validation: git diff --cached --check.

* components/net/af_unix: add local sockets

Add an opt-in AF_UNIX provider for pathname-based local IPC without
a synthetic network device.

Support datagram and stream sockets, blocking and nonblocking I/O,
timeouts, poll, socketpair, and SCM_RIGHTS descriptor passing. Include
bounded Kconfig settings, component documentation, and utest coverage.

Impact: enabled only by RT_USING_AF_UNIX and requires SAL POSIX with
DFSv2.
Validation: git diff --cached --check.

* Fix AF_UNIX CI checks

Apply the repository clang-format rules to the affected source lines.
Suppress the cppcheck false positive for the devtmpfs list iterator.

No functional behavior is changed.

* components/lwp: preserve NULL optional msghdr buffers

When msg_name or msg_control is NULL, keep the kernel pointer NULL
instead of substituting an uninitialized buffer. Reject a NULL control
buffer with a nonzero length as EFAULT.

Impact: LWP sendmsg/recvmsg conversion on MMU targets.
Validation: git diff --cached --check.

* components/net/af_unix: fix poll UAF, namespace leak, and SCM_RIGHTS cycles

Poll only the local wait queue and wake writers from the receiver.
Free namespace entries on detach, and reject AF_UNIX descriptors in
SCM_RIGHTS until cycle collection exists.

Impact: AF_UNIX poll, bind lifetime, and descriptor passing.
Validation: git diff --cached --check.

* components/dfs: add DFSv2 AF_UNIX utest suite

Add opt-in tests under dfs/utest/v2/af_unix for socket nodes, IPC,
poll peer-close, namespace cleanup, and SCM_RIGHTS rejection.

Sources are built only when RT_UTEST_TC_USING_DFS_V2_AF_UNIX and the
selected test groups are enabled.

Impact: DFS utest menu and build; no production AF_UNIX behavior change.
Validation: git diff --cached --check.

0 files changed, 0 insertions, 0 deletions