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.

1 files changed, 76 insertions, 0 deletions

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;
+}