Commit 5f57fbea authored by Tiwei Bie's avatar Tiwei Bie Committed by Michael S. Tsirkin
Browse files

vhost-user: allow slave to send fds via slave channel 



Introduce VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD protocol
feature to allow slave to send at most 8 descriptors
in each message to master via ancillary data using the
slave channel.

Suggested-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarTiwei Bie <tiwei.bie@intel.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 988a2775

docs/interop/vhost-user.txt

+5 −0
Original line number Diff line number Diff line
@@ -367,6 +367,10 @@ The fd is provided via VHOST_USER_SET_SLAVE_REQ_FD ancillary data. 
A slave may then send VHOST_USER_SLAVE_* messages to the master

using this fd communication channel.



If VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD protocol feature is negotiated,

slave can send file descriptors (at most 8 descriptors in each message)

to master via ancillary data using this fd communication channel.



Protocol features

-----------------
@@ -380,6 +384,7 @@ Protocol features 
#define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7

#define VHOST_USER_PROTOCOL_F_PAGEFAULT      8

#define VHOST_USER_PROTOCOL_F_CONFIG         9

#define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD  10



Master message types

--------------------

hw/virtio/vhost-user.c

+17 −10
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 


#define VHOST_MEMORY_MAX_NREGIONS    8

#define VHOST_USER_F_PROTOCOL_FEATURES 30

#define VHOST_USER_SLAVE_MAX_FDS     8



/*

 * Maximum size of virtio device config space
@@ -47,6 +48,7 @@ enum VhostUserProtocolFeature { 
    VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,

    VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,

    VHOST_USER_PROTOCOL_F_CONFIG = 9,

    VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,

    VHOST_USER_PROTOCOL_F_MAX

};
@@ -854,10 +856,10 @@ static void slave_read(void *opaque) 
    int size, ret = 0;

    struct iovec iov;

    struct msghdr msgh;

    int fd = -1;

    int fd[VHOST_USER_SLAVE_MAX_FDS];

    char control[CMSG_SPACE(sizeof(fd))];

    struct cmsghdr *cmsg;

    size_t fdsize;

    int i, fdsize = 0;



    memset(&msgh, 0, sizeof(msgh));

    msgh.msg_iov = &iov;
@@ -865,6 +867,8 @@ static void slave_read(void *opaque) 
    msgh.msg_control = control;

    msgh.msg_controllen = sizeof(control);



    memset(fd, -1, sizeof(fd));



    /* Read header */

    iov.iov_base = &hdr;

    iov.iov_len = VHOST_USER_HDR_SIZE;
@@ -885,7 +889,7 @@ static void slave_read(void *opaque) 
            if (cmsg->cmsg_level == SOL_SOCKET &&

                cmsg->cmsg_type == SCM_RIGHTS) {

                    fdsize = cmsg->cmsg_len - CMSG_LEN(0);

                    memcpy(&fd, CMSG_DATA(cmsg), fdsize);

                    memcpy(fd, CMSG_DATA(cmsg), fdsize);

                    break;

            }

    }
@@ -913,14 +917,15 @@ static void slave_read(void *opaque) 
        break;

    default:

        error_report("Received unexpected msg type.");

        if (fd != -1) {

            close(fd);

        }

        ret = -EINVAL;

    }



    /* Message handlers need to make sure that fd will be consumed. */

    fd = -1;

    /* Close the remaining file descriptors. */

    for (i = 0; i < fdsize; i++) {

        if (fd[i] != -1) {

            close(fd[i]);

        }

    }



    /*

     * REPLY_ACK feature handling. Other reply types has to be managed
@@ -954,8 +959,10 @@ err: 
    qemu_set_fd_handler(u->slave_fd, NULL, NULL, NULL);

    close(u->slave_fd);

    u->slave_fd = -1;

    if (fd != -1) {

        close(fd);

    for (i = 0; i < fdsize; i++) {

        if (fd[i] != -1) {

            close(fd[i]);

        }

    }

    return;

}