passthrough: fix unix-domain sockets on FreeBSD (#413)

FreeBSD doesn't allow creating sockets using mknod(2). Instead, one has to use socket(2)
and bind(2).  Add appropriate logic to the examples and add a test case.

3 files changed, 87 insertions, 19 deletions

diff --git a/example/passthrough.c b/example/passthrough.c
index da91930..6de9fc1 100644
--- a/example/passthrough.c
+++ b/example/passthrough.c
@@ -44,11 +44,17 @@
 #include <sys/stat.h>
 #include <dirent.h>
 #include <errno.h>
+#ifdef __FreeBSD__
+#include <sys/socket.h>
+#include <sys/un.h>
+#endif
 #include <sys/time.h>
 #ifdef HAVE_SETXATTR
 #include <sys/xattr.h>
 #endif
 
+#include "passthrough_helpers.h"
+
 static void *xmp_init(struct fuse_conn_info *conn,
 		      struct fuse_config *cfg)
 {
@@ -138,16 +144,7 @@ static int xmp_mknod(const char *path, mode_t mode, dev_t rdev)
 {
 	int res;
 
-	/* On Linux this could just be 'mknod(path, mode, rdev)' but this
-	   is more portable */
-	if (S_ISREG(mode)) {
-		res = open(path, O_CREAT | O_EXCL | O_WRONLY, mode);
-		if (res >= 0)
-			res = close(res);
-	} else if (S_ISFIFO(mode))
-		res = mkfifo(path, mode);
-	else
-		res = mknod(path, mode, rdev);
+	res = mknod_wrapper(AT_FDCWD, path, NULL, mode, rdev);
 	if (res == -1)
 		return -errno;
 
diff --git a/example/passthrough_helpers.h b/example/passthrough_helpers.h
new file mode 100644
index 0000000..6b77c33
--- /dev/null
+++ b/example/passthrough_helpers.h
@@ -0,0 +1,76 @@
+/*
+ * FUSE: Filesystem in Userspace
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE
+ */
+
+/*
+ * Creates files on the underlying file system in response to a FUSE_MKNOD
+ * operation
+ */
+static int mknod_wrapper(int dirfd, const char *path, const char *link,
+	int mode, dev_t rdev)
+{
+	int res;
+
+	if (S_ISREG(mode)) {
+		res = openat(dirfd, path, O_CREAT | O_EXCL | O_WRONLY, mode);
+		if (res >= 0)
+			res = close(res);
+	} else if (S_ISDIR(mode)) {
+		res = mkdirat(dirfd, path, mode);
+	} else if (S_ISLNK(mode) && link != NULL) {
+		res = symlinkat(link, dirfd, path);
+	} else if (S_ISFIFO(mode)) {
+		res = mkfifoat(dirfd, path, mode);
+#ifdef __FreeBSD__
+	} else if (S_ISSOCK(mode)) {
+		struct sockaddr_un su;
+		int fd;
+
+		if (strlen(path) >= sizeof(su.sun_path)) {
+			errno = ENAMETOOLONG;
+			return -1;
+		}
+		fd = socket(AF_UNIX, SOCK_STREAM, 0);
+		if (fd >= 0) {
+			/*
+			 * We must bind the socket to the underlying file
+			 * system to create the socket file, even though
+			 * we'll never listen on this socket.
+			 */
+			su.sun_family = AF_UNIX;
+			strncpy(su.sun_path, path, sizeof(su.sun_path));
+			res = bindat(dirfd, fd, (struct sockaddr*)&su,
+				sizeof(su));
+			if (res == 0)
+				close(fd);
+		} else {
+			res = -1;
+		}
+#endif
+	} else {
+		res = mknodat(dirfd, path, mode, rdev);
+	}
+
+	return res;
+}
diff --git a/example/passthrough_ll.c b/example/passthrough_ll.c
index b6ecaff..f0bc727 100644
--- a/example/passthrough_ll.c
+++ b/example/passthrough_ll.c
@@ -56,6 +56,8 @@
 #include <sys/file.h>
 #include <sys/xattr.h>
 
+#include "passthrough_helpers.h"
+
 /* We are re-using pointers to our `struct lo_inode` and `struct
    lo_dirp` elements as inodes. This means that we must be able to
    store uintptr_t values in a fuse_ino_t variable. The following
@@ -381,7 +383,6 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 			     const char *name, mode_t mode, dev_t rdev,
 			     const char *link)
 {
-	int newfd = -1;
 	int res;
 	int saverr;
 	struct lo_inode *dir = lo_inode(req, parent);
@@ -389,12 +390,8 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 
 	saverr = ENOMEM;
 
-	if (S_ISDIR(mode))
-		res = mkdirat(dir->fd, name, mode);
-	else if (S_ISLNK(mode))
-		res = symlinkat(link, dir->fd, name);
-	else
-		res = mknodat(dir->fd, name, mode, rdev);
+	res = mknod_wrapper(dir->fd, name, link, mode, rdev);
+
 	saverr = errno;
 	if (res == -1)
 		goto out;
@@ -411,8 +408,6 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 	return;
 
 out:
-	if (newfd != -1)
-		close(newfd);
 	fuse_reply_err(req, saverr);
 }