ivshmem-client.c

/*
 * Copyright 6WIND S.A., 2014
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * (at your option) any later version.  See the COPYING file in the
 * top-level directory.
 */

#include "qemu/osdep.h"
#include <sys/socket.h>
#include <sys/un.h>

#include "qemu/queue.h"

#include "ivshmem-client.h"

/* log a message on stdout if verbose=1 */
#define IVSHMEM_CLIENT_DEBUG(client, fmt, ...) do { \
        if ((client)->verbose) {         \
            printf(fmt, ## __VA_ARGS__); \
        }                                \
    } while (0)

/* read message from the unix socket */
static int
ivshmem_client_read_one_msg(IvshmemClient *client, int64_t *index, int *fd)
{
    int ret;
    struct msghdr msg;
    struct iovec iov[1];
    union {
        struct cmsghdr cmsg;
        char control[CMSG_SPACE(sizeof(int))];
    } msg_control;
    struct cmsghdr *cmsg;

    iov[0].iov_base = index;
    iov[0].iov_len = sizeof(*index);

    memset(&msg, 0, sizeof(msg));
    msg.msg_iov = iov;
    msg.msg_iovlen = 1;
    msg.msg_control = &msg_control;
    msg.msg_controllen = sizeof(msg_control);

    ret = recvmsg(client->sock_fd, &msg, 0);
    if (ret < sizeof(*index)) {
        IVSHMEM_CLIENT_DEBUG(client, "cannot read message: %s\n",
                             strerror(errno));
        return -1;
    }
    if (ret == 0) {
        IVSHMEM_CLIENT_DEBUG(client, "lost connection to server\n");
        return -1;
    }

    *index = GINT64_FROM_LE(*index);
    *fd = -1;

    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {

        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)) ||
            cmsg->cmsg_level != SOL_SOCKET ||
            cmsg->cmsg_type != SCM_RIGHTS) {
            continue;
        }

        memcpy(fd, CMSG_DATA(cmsg), sizeof(*fd));
    }

    return 0;
}

/* free a peer when the server advertises a disconnection or when the
 * client is freed */
static void
ivshmem_client_free_peer(IvshmemClient *client, IvshmemClientPeer *peer)
{
    unsigned vector;

    QTAILQ_REMOVE(&client->peer_list, peer, next);
    for (vector = 0; vector < peer->vectors_count; vector++) {
        close(peer->vectors[vector]);
    }

    g_free(peer);
}

/* handle message coming from server (new peer, new vectors) */
static int
ivshmem_client_handle_server_msg(IvshmemClient *client)
{
    IvshmemClientPeer *peer;
    int64_t peer_id;
    int ret, fd;

    ret = ivshmem_client_read_one_msg(client, &peer_id, &fd);
    if (ret < 0) {
        return -1;
    }

    /* can return a peer or the local client */
    peer = ivshmem_client_search_peer(client, peer_id);

    /* delete peer */
    if (fd == -1) {

        if (peer == NULL || peer == &client->local) {
            IVSHMEM_CLIENT_DEBUG(client, "receive delete for invalid "
                                 "peer %" PRId64 "\n", peer_id);
            return -1;
        }

        IVSHMEM_CLIENT_DEBUG(client, "delete peer id = %" PRId64 "\n", peer_id);
        ivshmem_client_free_peer(client, peer);
        return 0;
    }

    /* new peer */
    if (peer == NULL) {
        peer = g_malloc0(sizeof(*peer));
        peer->id = peer_id;
        peer->vectors_count = 0;
        QTAILQ_INSERT_TAIL(&client->peer_list, peer, next);
        IVSHMEM_CLIENT_DEBUG(client, "new peer id = %" PRId64 "\n", peer_id);
    }

    /* new vector */
    IVSHMEM_CLIENT_DEBUG(client, "  new vector %d (fd=%d) for peer id %"
                         PRId64 "\n", peer->vectors_count, fd, peer->id);
    if (peer->vectors_count >= G_N_ELEMENTS(peer->vectors)) {
        IVSHMEM_CLIENT_DEBUG(client, "Too many vectors received, failing");
        return -1;
    }

    peer->vectors[peer->vectors_count] = fd;
    peer->vectors_count++;

    return 0;
}

/* init a new ivshmem client */
int
ivshmem_client_init(IvshmemClient *client, const char *unix_sock_path,
                    IvshmemClientNotifCb notif_cb, void *notif_arg,
                    bool verbose)
{
    int ret;
    unsigned i;

    memset(client, 0, sizeof(*client));

    ret = snprintf(client->unix_sock_path, sizeof(client->unix_sock_path),
                   "%s", unix_sock_path);

    if (ret < 0 || ret >= sizeof(client->unix_sock_path)) {
        IVSHMEM_CLIENT_DEBUG(client, "could not copy unix socket path\n");
        return -1;
    }

    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
        client->local.vectors[i] = -1;
    }

    QTAILQ_INIT(&client->peer_list);
    client->local.id = -1;

    client->notif_cb = notif_cb;
    client->notif_arg = notif_arg;
    client->verbose = verbose;
    client->shm_fd = -1;
    client->sock_fd = -1;

    return 0;
}

/* create and connect to the unix socket */
int
ivshmem_client_connect(IvshmemClient *client)
{
    struct sockaddr_un s_un;
    int fd, ret;
    int64_t tmp;

    IVSHMEM_CLIENT_DEBUG(client, "connect to client %s\n",
                         client->unix_sock_path);

    client->sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (client->sock_fd < 0) {
        IVSHMEM_CLIENT_DEBUG(client, "cannot create socket: %s\n",
                             strerror(errno));
        return -1;
    }

    s_un.sun_family = AF_UNIX;
    ret = snprintf(s_un.sun_path, sizeof(s_un.sun_path), "%s",
                   client->unix_sock_path);
    if (ret < 0 || ret >= sizeof(s_un.sun_path)) {
        IVSHMEM_CLIENT_DEBUG(client, "could not copy unix socket path\n");
        goto err_close;
    }

    if (connect(client->sock_fd, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
        IVSHMEM_CLIENT_DEBUG(client, "cannot connect to %s: %s\n", s_un.sun_path,
                             strerror(errno));
        goto err_close;
    }

    /* first, we expect a protocol version */
    if (ivshmem_client_read_one_msg(client, &tmp, &fd) < 0 ||
        (tmp != IVSHMEM_PROTOCOL_VERSION) || fd != -1) {
        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server\n");
        goto err_close;
    }

    /* then, we expect our index + a fd == -1 */
    if (ivshmem_client_read_one_msg(client, &client->local.id, &fd) < 0 ||
        client->local.id < 0 || fd != -1) {
        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (2)\n");
        goto err_close;
    }
    IVSHMEM_CLIENT_DEBUG(client, "our_id=%" PRId64 "\n", client->local.id);

    /* now, we expect shared mem fd + a -1 index, note that shm fd
     * is not used */
    if (ivshmem_client_read_one_msg(client, &tmp, &fd) < 0 ||
        tmp != -1 || fd < 0) {
        if (fd >= 0) {
            close(fd);
        }
        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (3)\n");
        goto err_close;
    }
    client->shm_fd = fd;
    IVSHMEM_CLIENT_DEBUG(client, "shm_fd=%d\n", fd);

    return 0;

err_close:
    close(client->sock_fd);
    client->sock_fd = -1;
    return -1;
}

/* close connection to the server, and free all peer structures */
void
ivshmem_client_close(IvshmemClient *client)
{
    IvshmemClientPeer *peer;
    unsigned i;

    IVSHMEM_CLIENT_DEBUG(client, "close client\n");

    while ((peer = QTAILQ_FIRST(&client->peer_list)) != NULL) {
        ivshmem_client_free_peer(client, peer);
    }

    close(client->shm_fd);
    client->shm_fd = -1;
    close(client->sock_fd);
    client->sock_fd = -1;
    client->local.id = -1;
    for (i = 0; i < IVSHMEM_CLIENT_MAX_VECTORS; i++) {
        close(client->local.vectors[i]);
        client->local.vectors[i] = -1;
    }
    client->local.vectors_count = 0;
}

/* get the fd_set according to the unix socket and peer list */
void
ivshmem_client_get_fds(const IvshmemClient *client, fd_set *fds, int *maxfd)
{
    int fd;
    unsigned vector;

    FD_SET(client->sock_fd, fds);
    if (client->sock_fd >= *maxfd) {
        *maxfd = client->sock_fd + 1;
    }

    for (vector = 0; vector < client->local.vectors_count; vector++) {
        fd = client->local.vectors[vector];
        FD_SET(fd, fds);
        if (fd >= *maxfd) {
            *maxfd = fd + 1;
        }
    }
}

/* handle events from eventfd: just print a message on notification */
static int
ivshmem_client_handle_event(IvshmemClient *client, const fd_set *cur, int maxfd)
{
    IvshmemClientPeer *peer;
    uint64_t kick;
    unsigned i;
    int ret;

    peer = &client->local;

    for (i = 0; i < peer->vectors_count; i++) {
        if (peer->vectors[i] >= maxfd || !FD_ISSET(peer->vectors[i], cur)) {
            continue;
        }

        ret = read(peer->vectors[i], &kick, sizeof(kick));
        if (ret < 0) {
            return ret;
        }
        if (ret != sizeof(kick)) {
            IVSHMEM_CLIENT_DEBUG(client, "invalid read size = %d\n", ret);
            errno = EINVAL;
            return -1;
        }
        IVSHMEM_CLIENT_DEBUG(client, "received event on fd %d vector %d: %"
                             PRIu64 "\n", peer->vectors[i], i, kick);
        if (client->notif_cb != NULL) {
            client->notif_cb(client, peer, i, client->notif_arg);
        }
    }

    return 0;
}

/* read and handle new messages on the given fd_set */
int
ivshmem_client_handle_fds(IvshmemClient *client, fd_set *fds, int maxfd)
{
    if (client->sock_fd < maxfd && FD_ISSET(client->sock_fd, fds) &&
        ivshmem_client_handle_server_msg(client) < 0 && errno != EINTR) {
        IVSHMEM_CLIENT_DEBUG(client, "ivshmem_client_handle_server_msg() "
                             "failed\n");
        return -1;
    } else if (ivshmem_client_handle_event(client, fds, maxfd) < 0 &&
               errno != EINTR) {
        IVSHMEM_CLIENT_DEBUG(client, "ivshmem_client_handle_event() failed\n");
        return -1;
    }

    return 0;
}

/* send a notification on a vector of a peer */
int
ivshmem_client_notify(const IvshmemClient *client,
                      const IvshmemClientPeer *peer, unsigned vector)
{
    uint64_t kick;
    int fd;

    if (vector >= peer->vectors_count) {
        IVSHMEM_CLIENT_DEBUG(client, "invalid vector %u on peer %" PRId64 "\n",
                             vector, peer->id);
        return -1;
    }
    fd = peer->vectors[vector];
    IVSHMEM_CLIENT_DEBUG(client, "notify peer %" PRId64
                         " on vector %d, fd %d\n", peer->id, vector, fd);

    kick = 1;
    if (write(fd, &kick, sizeof(kick)) != sizeof(kick)) {
        fprintf(stderr, "could not write to %d: %s\n", peer->vectors[vector],
                strerror(errno));
        return -1;
    }
    return 0;
}

/* send a notification to all vectors of a peer */
int
ivshmem_client_notify_all_vects(const IvshmemClient *client,
                                const IvshmemClientPeer *peer)
{
    unsigned vector;
    int ret = 0;

    for (vector = 0; vector < peer->vectors_count; vector++) {
        if (ivshmem_client_notify(client, peer, vector) < 0) {
            ret = -1;
        }
    }

    return ret;
}

/* send a notification to all peers */
int
ivshmem_client_notify_broadcast(const IvshmemClient *client)
{
    IvshmemClientPeer *peer;
    int ret = 0;

    QTAILQ_FOREACH(peer, &client->peer_list, next) {
        if (ivshmem_client_notify_all_vects(client, peer) < 0) {
            ret = -1;
        }
    }

    return ret;
}

/* lookup peer from its id */
IvshmemClientPeer *
ivshmem_client_search_peer(IvshmemClient *client, int64_t peer_id)
{
    IvshmemClientPeer *peer;

    if (peer_id == client->local.id) {
        return &client->local;
    }

    QTAILQ_FOREACH(peer, &client->peer_list, next) {
        if (peer->id == peer_id) {
            return peer;
        }
    }
    return NULL;
}

/* dump our info, the list of peers their vectors on stdout */
void
ivshmem_client_dump(const IvshmemClient *client)
{
    const IvshmemClientPeer *peer;
    unsigned vector;

    /* dump local infos */
    peer = &client->local;
    printf("our_id = %" PRId64 "\n", peer->id);
    for (vector = 0; vector < peer->vectors_count; vector++) {
        printf("  vector %d is enabled (fd=%d)\n", vector,
               peer->vectors[vector]);
    }

    /* dump peers */
    QTAILQ_FOREACH(peer, &client->peer_list, next) {
        printf("peer_id = %" PRId64 "\n", peer->id);

        for (vector = 0; vector < peer->vectors_count; vector++) {
            printf("  vector %d is enabled (fd=%d)\n", vector,
                   peer->vectors[vector]);
        }
    }
}