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.

Author: BernardXiong

components/dfs/dfs_v2/filesystems/devfs/devtmpfs.c

@@ -27,6 +27,7 @@
 #define TMPFS_TYPE_FILE     0x00
 #define TMPFS_TYPE_DIR      0x01
 #define TMPFS_TYPE_DYN_DEV  0x02    /* dynamic device */
+#define TMPFS_TYPE_SOCKET   0x03
 
 struct devtmpfs_sb;
 
@@ -223,6 +224,7 @@ static struct devtmpfs_file *devtmpfs_file_lookup(struct devtmpfs_sb *superblock
             if (rt_strcmp(file->name, filename) == 0)
             {
                 rt_spin_unlock(&superblock->lock);
+                /* cppcheck-suppress uninitvar */
                 return file;
             }
         }
@@ -325,6 +327,10 @@ static int devtmpfs_getdents(struct dfs_file *file, struct dirent *dirp, uint32_
                 {
                     d->d_type = DT_DIR;
                 }
+                if (n_file->type == TMPFS_TYPE_SOCKET)
+                {
+                    d->d_type = DT_SOCK;
+                }
 
                 d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
                 rt_strncpy(d->d_name, n_file->name, DIRENT_NAME_MAX);
@@ -540,6 +546,14 @@ static struct dfs_vnode *devtmpfs_create_vnode(struct dfs_dentry *dentry, int ty
             vnode->mode &= ~S_IFMT;
             vnode->mode |= S_IFDIR;
         }
+        else if (type == FT_SOCKET ||
+                 (type == FT_REGULAR && S_ISSOCK(mode)))
+        {
+            d_file->type = TMPFS_TYPE_SOCKET;
+            vnode->type = FT_SOCKET;
+            vnode->mode &= ~S_IFMT;
+            vnode->mode |= S_IFSOCK;
+        }
         else
         {
             d_file->type = TMPFS_TYPE_FILE;
@@ -585,6 +599,10 @@ static struct dfs_vnode *devtmpfs_lookup(struct dfs_dentry *dentry)
             {
                 vnode->type = FT_DIRECTORY;
             }
+            else if (d_file->type == TMPFS_TYPE_SOCKET)
+            {
+                vnode->type = FT_SOCKET;
+            }
             else if (d_file->link)
             {
                 vnode->type = FT_SYMLINK;

components/dfs/dfs_v2/filesystems/tmpfs/dfs_tmpfs.c

@@ -535,6 +535,10 @@ static int dfs_tmpfs_getdents(struct dfs_file *file,
             {
                 d->d_type = DT_DIR;
             }
+            if (n_file->type == TMPFS_TYPE_SOCKET)
+            {
+                d->d_type = DT_SOCK;
+            }
             d->d_namlen = RT_NAME_MAX;
             d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
             rt_strncpy(d->d_name, n_file->name, TMPFS_NAME_MAX);
@@ -664,6 +668,11 @@ static struct dfs_vnode *_dfs_tmpfs_lookup(struct dfs_dentry *dentry)
                 vnode->mode = S_IFDIR | (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
                 vnode->type = FT_DIRECTORY;
             }
+            else if (d_file->type == TMPFS_TYPE_SOCKET)
+            {
+                vnode->mode = S_IFSOCK | (S_IRWXU | S_IRWXG | S_IRWXO);
+                vnode->type = FT_SOCKET;
+            }
             else
             {
                 vnode->mode = S_IFREG | (S_IRWXU | S_IRWXG | S_IRWXO);
@@ -750,6 +759,13 @@ static struct dfs_vnode *dfs_tmpfs_create_vnode(struct dfs_dentry *dentry, int t
             vnode->mode = S_IFDIR | (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
             vnode->type = FT_DIRECTORY;
         }
+        else if (type == FT_SOCKET ||
+                 (type == FT_REGULAR && S_ISSOCK(mode)))
+        {
+            d_file->type = TMPFS_TYPE_SOCKET;
+            vnode->mode = S_IFSOCK | (mode & (S_IRWXU | S_IRWXG | S_IRWXO));
+            vnode->type = FT_SOCKET;
+        }
         else
         {
             d_file->type = TMPFS_TYPE_FILE;

components/dfs/dfs_v2/filesystems/tmpfs/dfs_tmpfs.h

@@ -19,6 +19,7 @@
 
 #define TMPFS_TYPE_FILE   0x00
 #define TMPFS_TYPE_DIR    0x01
+#define TMPFS_TYPE_SOCKET 0x02
 
 struct tmpfs_sb;
 
@@ -46,4 +47,3 @@ struct tmpfs_sb
 int dfs_tmpfs_init(void);
 
 #endif
-

components/dfs/dfs_v2/include/dfs.h

@@ -134,6 +134,12 @@ int fdt_fd_associate_file(struct dfs_fdtable *fdt, int fd, struct dfs_file *file
 struct dfs_file *fd_get(int fd);
 void fd_release(int fd);
 
+/* Reference helpers used when an open file description crosses fd tables. */
+int dfs_file_get_refs(const int *fds, size_t count, struct dfs_file **files);
+/* Successful installation transfers the supplied references to the fd table. */
+int dfs_file_install_refs(struct dfs_file **files, size_t count, int *fds);
+void dfs_file_put_ref(struct dfs_file *file);
+
 void fd_init(struct dfs_file *fd);
 
 struct dfs_fdtable *dfs_fdtable_get(void);

components/dfs/dfs_v2/include/dfs_file.h

@@ -149,6 +149,7 @@ void dfs_file_init(struct dfs_file *file);
 void dfs_file_deinit(struct dfs_file *file);
 
 int dfs_file_open(struct dfs_file *file, const char *path, int flags, mode_t mode);
+int dfs_file_mknod(const char *path, int type, mode_t mode);
 int dfs_file_close(struct dfs_file *file);
 
 off_t dfs_file_get_fpos(struct dfs_file *file);

components/dfs/dfs_v2/src/dfs.c

@@ -349,23 +349,29 @@ int fdt_fd_new(struct dfs_fdtable *fdt)
  */
 void fdt_fd_release(struct dfs_fdtable *fdt, int fd)
 {
-    if (fd < fdt->maxfd)
+    if (fdt == RT_NULL || dfs_file_lock() != RT_EOK)
+    {
+        return;
+    }
+
+    if (fd >= 0 && fd < (int)fdt->maxfd)
     {
         struct dfs_file *file;
 
         file = fdt_get_file(fdt, fd);
 
-        if (file && file->ref_count == 1)
+        if (file != RT_NULL && file->ref_count == 1)
         {
             dfs_file_destroy(file);
         }
-        else
+        else if (file != RT_NULL)
         {
             rt_atomic_sub(&(file->ref_count), 1);
         }
 
         fdt->fds[fd] = RT_NULL;
     }
+    dfs_file_unlock();
 }
 
 /**
@@ -493,6 +499,106 @@ struct dfs_file *fd_get(int fd)
     return fdt_get_file(fdt, fd);
 }
 
+int dfs_file_get_refs(const int *fds, size_t count, struct dfs_file **files)
+{
+    size_t index;
+    struct dfs_fdtable *fdt;
+
+    if ((count != 0 && (fds == RT_NULL || files == RT_NULL)) ||
+        dfs_file_lock() != RT_EOK)
+    {
+        return -EINVAL;
+    }
+
+    fdt = dfs_fdtable_get();
+    for (index = 0; index < count; index++)
+    {
+        files[index] = fdt_get_file(fdt, fds[index]);
+        if (files[index] == RT_NULL ||
+            (files[index]->dentry == RT_NULL && files[index]->vnode == RT_NULL))
+        {
+            dfs_file_unlock();
+            return -EBADF;
+        }
+    }
+
+    for (index = 0; index < count; index++)
+    {
+        rt_atomic_add(&files[index]->ref_count, 1);
+    }
+    dfs_file_unlock();
+    return 0;
+}
+
+int dfs_file_install_refs(struct dfs_file **files, size_t count, int *fds)
+{
+    int fd;
+    int startfd;
+    size_t index;
+    struct dfs_fdtable *fdt;
+
+    if ((count != 0 && (files == RT_NULL || fds == RT_NULL)) ||
+        dfs_file_lock() != RT_EOK)
+    {
+        return -EINVAL;
+    }
+
+    fdt = dfs_fdtable_get();
+    startfd = (fdt == &_fdtab) ? DFS_STDIO_OFFSET : 0;
+    for (index = 0; index < count; index++)
+    {
+        if (files[index] == RT_NULL || files[index]->magic != DFS_FD_MAGIC)
+        {
+            break;
+        }
+
+        fd = _fdt_slot_alloc(fdt, startfd);
+        if (fd < 0)
+        {
+            break;
+        }
+        fdt->fds[fd] = files[index];
+        fds[index] = fd;
+    }
+
+    if (index != count)
+    {
+        while (index > 0)
+        {
+            index--;
+            fdt->fds[fds[index]] = RT_NULL;
+        }
+        dfs_file_unlock();
+        return -EMFILE;
+    }
+
+    dfs_file_unlock();
+    return 0;
+}
+
+void dfs_file_put_ref(struct dfs_file *file)
+{
+    if (file == RT_NULL || dfs_file_lock() != RT_EOK)
+    {
+        return;
+    }
+
+    if (file->magic == DFS_FD_MAGIC &&
+        rt_atomic_load(&file->ref_count) > 0 &&
+        dfs_file_close(file) == 0)
+    {
+        if (rt_atomic_load(&file->ref_count) == 1)
+        {
+            dfs_file_destroy(file);
+        }
+        else
+        {
+            rt_atomic_sub(&file->ref_count, 1);
+        }
+    }
+    dfs_file_unlock();
+}
+
 /**
  * This function will get the file descriptor table of current process.
  */
@@ -1238,4 +1344,4 @@ MSH_CMD_EXPORT(dfs_dlog, dfs dlog on|off);
 #endif
 
 #endif
-/** @} */
+/** @} */