example/hello_ll_uds.c - platform/external/libfuse - Git at Google

 /*
   FUSE: Filesystem in Userspace
   Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>
   Copyright (C) 2022  Tofik Sonono <tofik.sonono@intel.com>

   This program can be distributed under the terms of the GNU GPLv2.
   See the file COPYING.
 */

 /** @file
  *
  * minimal example filesystem using low-level API and a custom io. This custom
  * io is implemented using UNIX domain sockets (of type SOCK_STREAM)
  *
  * Compile with:
  *
  *     gcc -Wall hello_ll_uds.c `pkg-config fuse3 --cflags --libs` -o hello_ll_uds
  *
  * ## Source code ##
  * \include hello_ll.c
  */

 #define FUSE_USE_VERSION 34


 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif

 #include <fuse_lowlevel.h>
 #include <fuse_kernel.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <assert.h>
 #include <sys/socket.h>
 #include <sys/un.h>

 static const char *hello_str = "Hello World!\n";
 static const char *hello_name = "hello";

 static int hello_stat(fuse_ino_t ino, struct stat *stbuf)
 {
 	stbuf->st_ino = ino;
 	switch (ino) {
 	case 1:
 		stbuf->st_mode = S_IFDIR | 0755;
 		stbuf->st_nlink = 2;
 		break;

 	case 2:
 		stbuf->st_mode = S_IFREG | 0444;
 		stbuf->st_nlink = 1;
 		stbuf->st_size = strlen(hello_str);
 		break;

 	default:
 		return -1;
 	}
 	return 0;
 }

 static void hello_ll_getattr(fuse_req_t req, fuse_ino_t ino,
 			     struct fuse_file_info *fi)
 {
 	struct stat stbuf;

 	(void) fi;

 	memset(&stbuf, 0, sizeof(stbuf));
 	if (hello_stat(ino, &stbuf) == -1)
 		fuse_reply_err(req, ENOENT);
 	else
 		fuse_reply_attr(req, &stbuf, 1.0);
 }

 static void hello_ll_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
 {
 	struct fuse_entry_param e;

 	if (parent != 1 || strcmp(name, hello_name) != 0)
 		fuse_reply_err(req, ENOENT);
 	else {
 		memset(&e, 0, sizeof(e));
 		e.ino = 2;
 		e.attr_timeout = 1.0;
 		e.entry_timeout = 1.0;
 		hello_stat(e.ino, &e.attr);

 		fuse_reply_entry(req, &e);
 	}
 }

 struct dirbuf {
 	char *p;
 	size_t size;
 };

 static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
 		       fuse_ino_t ino)
 {
 	struct stat stbuf;
 	size_t oldsize = b->size;
 	b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
 	b->p = (char *) realloc(b->p, b->size);
 	memset(&stbuf, 0, sizeof(stbuf));
 	stbuf.st_ino = ino;
 	fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
 			  b->size);
 }

 #define min(x, y) ((x) < (y) ? (x) : (y))

 static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
 			     off_t off, size_t maxsize)
 {
 	if (off < bufsize)
 		return fuse_reply_buf(req, buf + off,
 				      min(bufsize - off, maxsize));
 	else
 		return fuse_reply_buf(req, NULL, 0);
 }

 static void hello_ll_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
 			     off_t off, struct fuse_file_info *fi)
 {
 	(void) fi;

 	if (ino != 1)
 		fuse_reply_err(req, ENOTDIR);
 	else {
 		struct dirbuf b;

 		memset(&b, 0, sizeof(b));
 		dirbuf_add(req, &b, ".", 1);
 		dirbuf_add(req, &b, "..", 1);
 		dirbuf_add(req, &b, hello_name, 2);
 		reply_buf_limited(req, b.p, b.size, off, size);
 		free(b.p);
 	}
 }

 static void hello_ll_open(fuse_req_t req, fuse_ino_t ino,
 			  struct fuse_file_info *fi)
 {
 	if (ino != 2)
 		fuse_reply_err(req, EISDIR);
 	else if ((fi->flags & O_ACCMODE) != O_RDONLY)
 		fuse_reply_err(req, EACCES);
 	else
 		fuse_reply_open(req, fi);
 }

 static void hello_ll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
 			  off_t off, struct fuse_file_info *fi)
 {
 	(void) fi;

 	assert(ino == 2);
 	reply_buf_limited(req, hello_str, strlen(hello_str), off, size);
 }

 static const struct fuse_lowlevel_ops hello_ll_oper = {
 	.lookup		= hello_ll_lookup,
 	.getattr	= hello_ll_getattr,
 	.readdir	= hello_ll_readdir,
 	.open		= hello_ll_open,
 	.read		= hello_ll_read,
 };

 static int create_socket(const char *socket_path) {
 	struct sockaddr_un addr;

 	if (strnlen(socket_path, sizeof(addr.sun_path)) >=
 		sizeof(addr.sun_path)) {
 		printf("Socket path may not be longer than %lu characters\n",
 			 sizeof(addr.sun_path) - 1);
 		return -1;
 	}

 	if (remove(socket_path) == -1 && errno != ENOENT) {
 		printf("Could not delete previous socket file entry at %s. Error: "
 			 "%s\n", socket_path, strerror(errno));
 		return -1;
 	}

 	memset(&addr, 0, sizeof(struct sockaddr_un));
 	strcpy(addr.sun_path, socket_path);

 	int sfd = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (sfd == -1) {
 		printf("Could not create socket. Error: %s\n", strerror(errno));
 		return -1;
 	}

 	addr.sun_family = AF_UNIX;
 	if (bind(sfd, (struct sockaddr *) &addr,
 		   sizeof(struct sockaddr_un)) == -1) {
 		printf("Could not bind socket. Error: %s\n", strerror(errno));
 		return -1;
 	}

 	if (listen(sfd, 1) == -1)
 		return -1;

 	printf("Awaiting connection on socket at %s...\n", socket_path);
 	int cfd = accept(sfd, NULL, NULL);
 	if (cfd == -1) {
 		printf("Could not accept connection. Error: %s\n",
 			 strerror(errno));
 		return -1;
 	} else {
 		printf("Accepted connection!\n");
 	}
 	return cfd;
 }

 static ssize_t stream_writev(int fd, struct iovec *iov, int count,
                              void *userdata) {
 	(void)userdata;

 	ssize_t written = 0;
 	int cur = 0;
 	for (;;) {
 		written = writev(fd, iov+cur, count-cur);
 		if (written < 0)
 			return written;

 		while (cur < count && written >= iov[cur].iov_len)
 			written -= iov[cur++].iov_len;
 		if (cur == count)
 			break;

 		iov[cur].iov_base = (char *)iov[cur].iov_base + written;
 		iov[cur].iov_len -= written;
 	}
 	return written;
 }


 static ssize_t readall(int fd, void *buf, size_t len) {
 	size_t count = 0;

 	while (count < len) {
 		int i = read(fd, (char *)buf + count, len - count);
 		if (!i)
 			break;

 		if (i < 0)
 			return i;

 		count += i;
 	}
 	return count;
 }

 static ssize_t stream_read(int fd, void *buf, size_t buf_len, void *userdata) {
     (void)userdata;

 	int res = readall(fd, buf, sizeof(struct fuse_in_header));
 	if (res == -1)
     	return res;


     uint32_t packet_len = ((struct fuse_in_header *)buf)->len;
     if (packet_len > buf_len)
     	return -1;

     int prev_res = res;

     res = readall(fd, (char *)buf + sizeof(struct fuse_in_header),
                   packet_len - sizeof(struct fuse_in_header));

     return  (res == -1) ? res : (res + prev_res);
 }

 static ssize_t stream_splice_send(int fdin, off_t *offin, int fdout,
 					    off_t *offout, size_t len,
                                   unsigned int flags, void *userdata) {
 	(void)userdata;

 	size_t count = 0;
 	while (count < len) {
 		int i = splice(fdin, offin, fdout, offout, len - count, flags);
 		if (i < 1)
 			return i;

 		count += i;
 	}
 	return count;
 }

 static void fuse_cmdline_help_uds(void)
 {
 	printf("    -h   --help            print help\n"
 	       "    -V   --version         print version\n"
 	       "    -d   -o debug          enable debug output (implies -f)\n");
 }

 int main(int argc, char *argv[])
 {
 	struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
 	struct fuse_session *se;
 	struct fuse_cmdline_opts opts;
 	const struct fuse_custom_io io = {
 		.writev = stream_writev,
 		.read = stream_read,
 		.splice_receive = NULL,
 		.splice_send = stream_splice_send,
 	};
 	int cfd = -1;
 	int ret = -1;

 	if (fuse_parse_cmdline(&args, &opts) != 0)
 		return 1;
 	if (opts.show_help) {
 		printf("usage: %s [options]\n\n", argv[0]);
 		fuse_cmdline_help_uds();
 		fuse_lowlevel_help();
 		ret = 0;
 		goto err_out1;
 	} else if (opts.show_version) {
 		printf("FUSE library version %s\n", fuse_pkgversion());
 		fuse_lowlevel_version();
 		ret = 0;
 		goto err_out1;
 	}

 	se = fuse_session_new(&args, &hello_ll_oper,
 			      sizeof(hello_ll_oper), NULL);
 	if (se == NULL)
 	    goto err_out1;

 	if (fuse_set_signal_handlers(se) != 0)
 	    goto err_out2;

 	cfd = create_socket("/tmp/libfuse-hello-ll.sock");
 	if (cfd == -1)
 		goto err_out3;

 	if (fuse_session_custom_io(se, &io, cfd) != 0)
 		goto err_out3;

 	/* Block until ctrl+c */
 	ret = fuse_session_loop(se);
 err_out3:
 	fuse_remove_signal_handlers(se);
 err_out2:
 	fuse_session_destroy(se);
 err_out1:
 	free(opts.mountpoint);
 	fuse_opt_free_args(&args);

 	return ret ? 1 : 0;
 }
	/*
	FUSE: Filesystem in Userspace
	Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
	Copyright (C) 2022 Tofik Sonono <tofik.sonono@intel.com>

	This program can be distributed under the terms of the GNU GPLv2.
	See the file COPYING.
	*/

	/** @file
	*
	* minimal example filesystem using low-level API and a custom io. This custom
	* io is implemented using UNIX domain sockets (of type SOCK_STREAM)
	*
	* Compile with:
	*
	* gcc -Wall hello_ll_uds.c `pkg-config fuse3 --cflags --libs` -o hello_ll_uds
	*
	* ## Source code ##
	* \include hello_ll.c
	*/

	#define FUSE_USE_VERSION 34


	#ifndef _GNU_SOURCE
	#define _GNU_SOURCE
	#endif

	#include <fuse_lowlevel.h>
	#include <fuse_kernel.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <unistd.h>
	#include <assert.h>
	#include <sys/socket.h>
	#include <sys/un.h>

	static const char *hello_str = "Hello World!\n";
	static const char *hello_name = "hello";

	static int hello_stat(fuse_ino_t ino, struct stat *stbuf)
	{
	stbuf->st_ino = ino;
	switch (ino) {
	case 1:
	stbuf->st_mode = S_IFDIR \| 0755;
	stbuf->st_nlink = 2;
	break;

	case 2:
	stbuf->st_mode = S_IFREG \| 0444;
	stbuf->st_nlink = 1;
	stbuf->st_size = strlen(hello_str);
	break;

	default:
	return -1;
	}
	return 0;
	}

	static void hello_ll_getattr(fuse_req_t req, fuse_ino_t ino,
	struct fuse_file_info *fi)
	{
	struct stat stbuf;

	(void) fi;

	memset(&stbuf, 0, sizeof(stbuf));
	if (hello_stat(ino, &stbuf) == -1)
	fuse_reply_err(req, ENOENT);
	else
	fuse_reply_attr(req, &stbuf, 1.0);
	}

	static void hello_ll_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
	{
	struct fuse_entry_param e;

	if (parent != 1 \|\| strcmp(name, hello_name) != 0)
	fuse_reply_err(req, ENOENT);
	else {
	memset(&e, 0, sizeof(e));
	e.ino = 2;
	e.attr_timeout = 1.0;
	e.entry_timeout = 1.0;
	hello_stat(e.ino, &e.attr);

	fuse_reply_entry(req, &e);
	}
	}

	struct dirbuf {
	char *p;
	size_t size;
	};

	static void dirbuf_add(fuse_req_t req, struct dirbuf b, const char name,
	fuse_ino_t ino)
	{
	struct stat stbuf;
	size_t oldsize = b->size;
	b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
	b->p = (char *) realloc(b->p, b->size);
	memset(&stbuf, 0, sizeof(stbuf));
	stbuf.st_ino = ino;
	fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
	b->size);
	}

	#define min(x, y) ((x) < (y) ? (x) : (y))

	static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
	off_t off, size_t maxsize)
	{
	if (off < bufsize)
	return fuse_reply_buf(req, buf + off,
	min(bufsize - off, maxsize));
	else
	return fuse_reply_buf(req, NULL, 0);
	}

	static void hello_ll_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
	off_t off, struct fuse_file_info *fi)
	{
	(void) fi;

	if (ino != 1)
	fuse_reply_err(req, ENOTDIR);
	else {
	struct dirbuf b;

	memset(&b, 0, sizeof(b));
	dirbuf_add(req, &b, ".", 1);
	dirbuf_add(req, &b, "..", 1);
	dirbuf_add(req, &b, hello_name, 2);
	reply_buf_limited(req, b.p, b.size, off, size);
	free(b.p);
	}
	}

	static void hello_ll_open(fuse_req_t req, fuse_ino_t ino,
	struct fuse_file_info *fi)
	{
	if (ino != 2)
	fuse_reply_err(req, EISDIR);
	else if ((fi->flags & O_ACCMODE) != O_RDONLY)
	fuse_reply_err(req, EACCES);
	else
	fuse_reply_open(req, fi);
	}

	static void hello_ll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
	off_t off, struct fuse_file_info *fi)
	{
	(void) fi;

	assert(ino == 2);
	reply_buf_limited(req, hello_str, strlen(hello_str), off, size);
	}

	static const struct fuse_lowlevel_ops hello_ll_oper = {
	.lookup = hello_ll_lookup,
	.getattr = hello_ll_getattr,
	.readdir = hello_ll_readdir,
	.open = hello_ll_open,
	.read = hello_ll_read,
	};

	static int create_socket(const char *socket_path) {
	struct sockaddr_un addr;

	if (strnlen(socket_path, sizeof(addr.sun_path)) >=
	sizeof(addr.sun_path)) {
	printf("Socket path may not be longer than %lu characters\n",
	sizeof(addr.sun_path) - 1);
	return -1;
	}

	if (remove(socket_path) == -1 && errno != ENOENT) {
	printf("Could not delete previous socket file entry at %s. Error: "
	"%s\n", socket_path, strerror(errno));
	return -1;
	}

	memset(&addr, 0, sizeof(struct sockaddr_un));
	strcpy(addr.sun_path, socket_path);

	int sfd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sfd == -1) {
	printf("Could not create socket. Error: %s\n", strerror(errno));
	return -1;
	}

	addr.sun_family = AF_UNIX;
	if (bind(sfd, (struct sockaddr *) &addr,
	sizeof(struct sockaddr_un)) == -1) {
	printf("Could not bind socket. Error: %s\n", strerror(errno));
	return -1;
	}

	if (listen(sfd, 1) == -1)
	return -1;

	printf("Awaiting connection on socket at %s...\n", socket_path);
	int cfd = accept(sfd, NULL, NULL);
	if (cfd == -1) {
	printf("Could not accept connection. Error: %s\n",
	strerror(errno));
	return -1;
	} else {
	printf("Accepted connection!\n");
	}
	return cfd;
	}

	static ssize_t stream_writev(int fd, struct iovec *iov, int count,
	void *userdata) {
	(void)userdata;

	ssize_t written = 0;
	int cur = 0;
	for (;;) {
	written = writev(fd, iov+cur, count-cur);
	if (written < 0)
	return written;

	while (cur < count && written >= iov[cur].iov_len)
	written -= iov[cur++].iov_len;
	if (cur == count)
	break;

	iov[cur].iov_base = (char *)iov[cur].iov_base + written;
	iov[cur].iov_len -= written;
	}
	return written;
	}


	static ssize_t readall(int fd, void *buf, size_t len) {
	size_t count = 0;

	while (count < len) {
	int i = read(fd, (char *)buf + count, len - count);
	if (!i)
	break;

	if (i < 0)
	return i;

	count += i;
	}
	return count;
	}

	static ssize_t stream_read(int fd, void buf, size_t buf_len, void userdata) {
	(void)userdata;

	int res = readall(fd, buf, sizeof(struct fuse_in_header));
	if (res == -1)
	return res;


	uint32_t packet_len = ((struct fuse_in_header *)buf)->len;
	if (packet_len > buf_len)
	return -1;

	int prev_res = res;

	res = readall(fd, (char *)buf + sizeof(struct fuse_in_header),
	packet_len - sizeof(struct fuse_in_header));

	return (res == -1) ? res : (res + prev_res);
	}

	static ssize_t stream_splice_send(int fdin, off_t *offin, int fdout,
	off_t *offout, size_t len,
	unsigned int flags, void *userdata) {
	(void)userdata;

	size_t count = 0;
	while (count < len) {
	int i = splice(fdin, offin, fdout, offout, len - count, flags);
	if (i < 1)
	return i;

	count += i;
	}
	return count;
	}

	static void fuse_cmdline_help_uds(void)
	{
	printf(" -h --help print help\n"
	" -V --version print version\n"
	" -d -o debug enable debug output (implies -f)\n");
	}

	int main(int argc, char *argv[])
	{
	struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
	struct fuse_session *se;
	struct fuse_cmdline_opts opts;
	const struct fuse_custom_io io = {
	.writev = stream_writev,
	.read = stream_read,
	.splice_receive = NULL,
	.splice_send = stream_splice_send,
	};
	int cfd = -1;
	int ret = -1;

	if (fuse_parse_cmdline(&args, &opts) != 0)
	return 1;
	if (opts.show_help) {
	printf("usage: %s [options]\n\n", argv[0]);
	fuse_cmdline_help_uds();
	fuse_lowlevel_help();
	ret = 0;
	goto err_out1;
	} else if (opts.show_version) {
	printf("FUSE library version %s\n", fuse_pkgversion());
	fuse_lowlevel_version();
	ret = 0;
	goto err_out1;
	}

	se = fuse_session_new(&args, &hello_ll_oper,
	sizeof(hello_ll_oper), NULL);
	if (se == NULL)
	goto err_out1;

	if (fuse_set_signal_handlers(se) != 0)
	goto err_out2;

	cfd = create_socket("/tmp/libfuse-hello-ll.sock");
	if (cfd == -1)
	goto err_out3;

	if (fuse_session_custom_io(se, &io, cfd) != 0)
	goto err_out3;

	/* Block until ctrl+c */
	ret = fuse_session_loop(se);
	err_out3:
	fuse_remove_signal_handlers(se);
	err_out2:
	fuse_session_destroy(se);
	err_out1:
	free(opts.mountpoint);
	fuse_opt_free_args(&args);

	return ret ? 1 : 0;
	}