hello_ll_uds.c

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/*
  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 GPL2.txt.
*/

 
#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";
 
#define DEFAULT_SOCKET_PATH "/tmp/libfuse-hello-ll.sock"
 
static struct options {
        const char *socket_path;
} options;
 
#define OPTION(t, p)                           \
        { t, offsetof(struct options, p), 1 }
static const struct fuse_opt option_spec[] = {
        OPTION("--socket=%s", socket_path),
        FUSE_OPT_END
};
 
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_init(void *userdata, struct fuse_conn_info *conn)
{
        (void)userdata;
 
        /* Disable the receiving and processing of FUSE_INTERRUPT requests */
        conn->no_interrupt = 1;
}
 
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 = {
        .init           = hello_ll_init,
        .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 %zu 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"
               "    --socket=PATH          serve on PATH\n"
               "                           (default: " DEFAULT_SOCKET_PATH ")\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;
 
        /* strdup: fuse_opt_parse frees the old value if --socket is given */
        options.socket_path = strdup(DEFAULT_SOCKET_PATH);
        if (options.socket_path == NULL)
                return 1;
 
        if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
                return 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(options.socket_path);
        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;
}