Re: [fuse-devel] [RFC v1] Support using socket fd as the fuse device

[Feng S. <ste...@gm...>]

Hi,

I also made a quick & dirty example code by modifying the passthrough_ll.c
for both unix domain socket client&server, which is at:
https://github.com/openunix/hsfs2/blob/master/hsfs/hsfs_main.c

Compile it with gcc -Wall hsfs_main.c `pkg-config fuse3 --cflags --libs` -o
example. I will try to add VSOCK/VMCI later.

Thanks.

-- Feng Shuo

2017-10-16 21:39 GMT+08:00 Feng Shuo <ste...@gm...>:

> This patch introduces a new fuse low level function fuse_session_socket()
> to enable using a socket fd as the fuse device. This helps to implement
> separated fuse daemon with its mount points, especially by unix domain
> socket in one system, or VSOCK/VMCI socket between VM and Host.
>
> Currently only single-thread mode is supported in this "socket" mode.
>
> Signed-off-by: Feng Shuo <ste...@gm...>
> ---
>  include/fuse_lowlevel.h |  10 +++++
>  lib/fuse_i.h            |   1 +
>  lib/fuse_loop_mt.c      |   5 +++
>  lib/fuse_lowlevel.c     | 117 ++++++++++++++++++++++++++++++
> ++++++++++++++++--
>  lib/fuse_versionscript  |   1 +
>  5 files changed, 131 insertions(+), 3 deletions(-)
>
> diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
> index efe4edb..8bf281f 100644
> --- a/include/fuse_lowlevel.h
> +++ b/include/fuse_lowlevel.h
> @@ -1955,6 +1955,16 @@ void fuse_session_process_buf(struct fuse_session
> *se,
>   */
>  int fuse_session_receive_buf(struct fuse_session *se, struct fuse_buf
> *buf);
>
> +/**
> + * Set FUSE file system to run on a socket.
> + *
> + * @param se session object
> + * @param socket the socket fd to run with
> + *
> + * @return 0 on success, -1 on failure.
> + **/
> +int fuse_session_socket(struct fuse_session *se, int sock);
> +
>  #ifdef __cplusplus
>  }
>  #endif
> diff --git a/lib/fuse_i.h b/lib/fuse_i.h
> index 54466f6..978d610 100644
> --- a/lib/fuse_i.h
> +++ b/lib/fuse_i.h
> @@ -64,6 +64,7 @@ struct fuse_session {
>         struct fuse_notify_req notify_list;
>         size_t bufsize;
>         int error;
> +       int use_socket;
>  };
>
>  struct fuse_chan {
> diff --git a/lib/fuse_loop_mt.c b/lib/fuse_loop_mt.c
> index 42d3e03..0adacc3 100644
> --- a/lib/fuse_loop_mt.c
> +++ b/lib/fuse_loop_mt.c
> @@ -306,6 +306,11 @@ int fuse_session_loop_mt(struct fuse_session *se, int
> clone_fd)
>         struct fuse_mt mt;
>         struct fuse_worker *w;
>
> +       /* Multi-thread not supported for socket mode */
> +       if (se->use_socket) {
> +               fprintf(stderr, "fuse: multi-threaded not supported on
> socket mode.\n");
> +               return -ENOTSUP;
> +       }
>         memset(&mt, 0, sizeof(struct fuse_mt));
>         mt.se = se;
>         mt.clone_fd = clone_fd;
> diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
> index ccdb5a5..8392195 100644
> --- a/lib/fuse_lowlevel.c
> +++ b/lib/fuse_lowlevel.c
> @@ -26,6 +26,7 @@
>  #include <errno.h>
>  #include <assert.h>
>  #include <sys/file.h>
> +#include <sys/socket.h>
>
>  #ifndef F_LINUX_SPECIFIC_BASE
>  #define F_LINUX_SPECIFIC_BASE       1024
> @@ -2617,6 +2618,92 @@ int fuse_session_receive_buf(struct fuse_session
> *se, struct fuse_buf *buf)
>         return fuse_session_receive_buf_int(se, buf, NULL);
>  }
>
> +static int fuse_sock_recv(int fd, void *data, int len, int flags)
> +{
> +       int saved = len;
> +
> +       while (len > 0) {
> +               int res;
> +
> +               res = recv(fd, data, len, flags);
> +               if ((res == -1) && (errno == EAGAIN))
> +                       continue;
> +               if ((res == -1) || (res == 0))
> +                       return res;
> +
> +               /* Re-do the entire read if reading header */
> +               if ((res != len) && (flags & MSG_PEEK))
> +                       continue;
> +
> +               len -= res;
> +       }
> +
> +       return saved;
> +}
> +
> +static int fuse_sock_read_req(int fd, void *data, int maxlen)
> +{
> +       struct fuse_in_header header;
> +       int res;
> +
> +       res = fuse_sock_recv(fd, &header, sizeof(header), MSG_PEEK);
> +       if (res < sizeof(header))
> +               goto out;       /* -1 or 0 */
> +
> +       if (maxlen < header.len) {
> +               fprintf(stderr,
> +                       "fuse: fuse_sock_read_req: buffer size too small: "
> +                       "%d, required %d\n",
> +                       maxlen, header.len);
> +               res = -1;
> +               errno = -EIO;
> +               goto out;
> +       }
> +
> +       res = fuse_sock_recv(fd, data, header.len, 0);
> +out:
> +       return res;
> +}
> +
> +#ifdef HAVE_SPLICE
> +static int fuse_sock_splice_req(int from, int to, int maxlen, int flags)
> +{
> +       struct fuse_in_header header;
> +       int res, len;
> +
> +       res = fuse_sock_recv(from, &header, sizeof(header), MSG_PEEK);
> +       if (res < sizeof(header))
> +               goto out;       /* -1 or 0 */
> +
> +       if (maxlen < header.len) {
> +               fprintf(stderr,
> +                       "fuse: fuse_sock_splice_req: buffer size too
> small: "
> +                       "%d, required %d\n",
> +                       maxlen, header.len);
> +               res = -1;
> +               errno = -EIO;
> +               goto out;
> +       }
> +
> +       len = header.len;
> +       while (len > 0) {
> +               res = splice(from, NULL, to, NULL, len, flags);
> +               if ((res == -1) && (errno == EAGAIN))
> +                       continue;
> +               if ((res == -1) || (res == 0))
> +                       goto out;
> +               len -= res;
> +       }
> +
> +       return header.len;
> +
> +out:
> +       return res;
> +}
> +#endif
> +
> +
> +
>  int fuse_session_receive_buf_int(struct fuse_session *se, struct
> fuse_buf *buf,
>                                  struct fuse_chan *ch)
>  {
> @@ -2647,8 +2734,16 @@ int fuse_session_receive_buf_int(struct
> fuse_session *se, struct fuse_buf *buf,
>                         goto fallback;
>         }
>
> -       res = splice(ch ? ch->fd : se->fd,
> -                    NULL, llp->pipe[1], NULL, bufsize, 0);
> +       if (se->use_socket){
> +               res = fuse_sock_splice_req(ch ? ch->fd : se->fd,
> +                                          llp->pipe[1], bufsize, 0);
> +               if (res == 0)
> +                       fuse_session_exit(se);
> +       }
> +       else {
> +               res = splice(ch ? ch->fd : se->fd,
> +                            NULL, llp->pipe[1], NULL, bufsize, 0);
> +       }
>         err = errno;
>
>         if (fuse_session_exited(se))
> @@ -2734,7 +2829,14 @@ fallback:
>         }
>
>  restart:
> -       res = read(ch ? ch->fd : se->fd, buf->mem, se->bufsize);
> +       if (se->use_socket){
> +               res = fuse_sock_read_req(ch ? ch->fd : se->fd, buf->mem,
> se->bufsize);
> +               if (res == 0)
> +                       fuse_session_exit(se);
> +       }
> +       else{
> +               res = read(ch ? ch->fd : se->fd, buf->mem, se->bufsize);
> +       }
>         err = errno;
>
>         if (fuse_session_exited(se))
> @@ -2851,6 +2953,7 @@ struct fuse_session *fuse_session_new(struct
> fuse_args *args,
>         memcpy(&se->op, op, op_size);
>         se->owner = getuid();
>         se->userdata = userdata;
> +       se->use_socket = 0;
>
>         se->mo = mo;
>         return se;
> @@ -2899,6 +3002,14 @@ error_out:
>         return -1;
>  }
>
> +int fuse_session_socket(struct fuse_session *se, int sock)
> +{
> +       se->fd = sock;
> +       se->mountpoint = NULL;
> +       se->use_socket = 1;
> +       return 0;
> +}
> +
>  int fuse_session_fd(struct fuse_session *se)
>  {
>         return se->fd;
> diff --git a/lib/fuse_versionscript b/lib/fuse_versionscript
> index 5fa3264..ceb5c1c 100644
> --- a/lib/fuse_versionscript
> +++ b/lib/fuse_versionscript
> @@ -136,6 +136,7 @@ FUSE_3.1 {
>         global:
>                 fuse_lib_help;
>                 fuse_new_30;
> +               fuse_session_socket;
>  } FUSE_3.0;
>
>  # Local Variables:
> --
> 1.8.3.1
>
>