contrib/ivshmem-server/ivshmem-server.c - third_party/qemu - Git at Google

 /*
  * 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 "qemu/host-utils.h"
 #include "qemu/sockets.h"

 #include <sys/socket.h>
 #include <sys/un.h>

 #include "ivshmem-server.h"

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

 /** maximum size of a huge page, used by ivshmem_server_ftruncate() */
 #define IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE (1024 * 1024 * 1024)

 /** default listen backlog (number of sockets not accepted) */
 #define IVSHMEM_SERVER_LISTEN_BACKLOG 10

 /* send message to a client unix socket */
 static int
 ivshmem_server_send_one_msg(int sock_fd, int64_t peer_id, 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;

     peer_id = GINT64_TO_LE(peer_id);
     iov[0].iov_base = &peer_id;
     iov[0].iov_len = sizeof(peer_id);

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

     /* if fd is specified, add it in a cmsg */
     if (fd >= 0) {
         memset(&msg_control, 0, sizeof(msg_control));
         msg.msg_control = &msg_control;
         msg.msg_controllen = sizeof(msg_control);
         cmsg = CMSG_FIRSTHDR(&msg);
         cmsg->cmsg_level = SOL_SOCKET;
         cmsg->cmsg_type = SCM_RIGHTS;
         cmsg->cmsg_len = CMSG_LEN(sizeof(int));
         memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
     }

     ret = sendmsg(sock_fd, &msg, 0);
     if (ret <= 0) {
         return -1;
     }

     return 0;
 }

 /* free a peer when the server advertises a disconnection or when the
  * server is freed */
 static void
 ivshmem_server_free_peer(IvshmemServer *server, IvshmemServerPeer *peer)
 {
     unsigned vector;
     IvshmemServerPeer *other_peer;

     IVSHMEM_SERVER_DEBUG(server, "free peer %" PRId64 "\n", peer->id);
     close(peer->sock_fd);
     QTAILQ_REMOVE(&server->peer_list, peer, next);

     /* advertise the deletion to other peers */
     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
         ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id, -1);
     }

     for (vector = 0; vector < peer->vectors_count; vector++) {
         event_notifier_cleanup(&peer->vectors[vector]);
     }

     g_free(peer);
 }

 /* send the peer id and the shm_fd just after a new client connection */
 static int
 ivshmem_server_send_initial_info(IvshmemServer *server, IvshmemServerPeer *peer)
 {
     int ret;

     /* send our protocol version first */
     ret = ivshmem_server_send_one_msg(peer->sock_fd, IVSHMEM_PROTOCOL_VERSION,
                                       -1);
     if (ret < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot send version: %s\n",
                              strerror(errno));
         return -1;
     }

     /* send the peer id to the client */
     ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);
     if (ret < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot send peer id: %s\n",
                              strerror(errno));
         return -1;
     }

     /* send the shm_fd */
     ret = ivshmem_server_send_one_msg(peer->sock_fd, -1, server->shm_fd);
     if (ret < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot send shm fd: %s\n",
                              strerror(errno));
         return -1;
     }

     return 0;
 }

 /* handle message on listening unix socket (new client connection) */
 static int
 ivshmem_server_handle_new_conn(IvshmemServer *server)
 {
     IvshmemServerPeer *peer, *other_peer;
     struct sockaddr_un unaddr;
     socklen_t unaddr_len;
     int newfd;
     unsigned i;

     /* accept the incoming connection */
     unaddr_len = sizeof(unaddr);
     newfd = qemu_accept(server->sock_fd,
                         (struct sockaddr *)&unaddr, &unaddr_len);

     if (newfd < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot accept() %s\n", strerror(errno));
         return -1;
     }

     qemu_socket_set_nonblock(newfd);
     IVSHMEM_SERVER_DEBUG(server, "accept()=%d\n", newfd);

     /* allocate new structure for this peer */
     peer = g_malloc0(sizeof(*peer));
     peer->sock_fd = newfd;

     /* get an unused peer id */
     /* XXX: this could use id allocation such as Linux IDA, or simply
      * a free-list */
     for (i = 0; i < G_MAXUINT16; i++) {
         if (ivshmem_server_search_peer(server, server->cur_id) == NULL) {
             break;
         }
         server->cur_id++;
     }
     if (i == G_MAXUINT16) {
         IVSHMEM_SERVER_DEBUG(server, "cannot allocate new client id\n");
         close(newfd);
         g_free(peer);
         return -1;
     }
     peer->id = server->cur_id++;

     /* create eventfd, one per vector */
     peer->vectors_count = server->n_vectors;
     for (i = 0; i < peer->vectors_count; i++) {
         if (event_notifier_init(&peer->vectors[i], FALSE) < 0) {
             IVSHMEM_SERVER_DEBUG(server, "cannot create eventfd\n");
             goto fail;
         }
     }

     /* send peer id and shm fd */
     if (ivshmem_server_send_initial_info(server, peer) < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot send initial info\n");
         goto fail;
     }

     /* advertise the new peer to others */
     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
         for (i = 0; i < peer->vectors_count; i++) {
             ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id,
                                         peer->vectors[i].wfd);
         }
     }

     /* advertise the other peers to the new one */
     QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
         for (i = 0; i < peer->vectors_count; i++) {
             ivshmem_server_send_one_msg(peer->sock_fd, other_peer->id,
                                         other_peer->vectors[i].wfd);
         }
     }

     /* advertise the new peer to itself */
     for (i = 0; i < peer->vectors_count; i++) {
         ivshmem_server_send_one_msg(peer->sock_fd, peer->id,
                                     event_notifier_get_fd(&peer->vectors[i]));
     }

     QTAILQ_INSERT_TAIL(&server->peer_list, peer, next);
     IVSHMEM_SERVER_DEBUG(server, "new peer id = %" PRId64 "\n",
                          peer->id);
     return 0;

 fail:
     while (i--) {
         event_notifier_cleanup(&peer->vectors[i]);
     }
     close(newfd);
     g_free(peer);
     return -1;
 }

 /* Try to ftruncate a file to next power of 2 of shmsize.
  * If it fails; all power of 2 above shmsize are tested until
  * we reach the maximum huge page size. This is useful
  * if the shm file is in a hugetlbfs that cannot be truncated to the
  * shm_size value. */
 static int
 ivshmem_server_ftruncate(int fd, unsigned shmsize)
 {
     int ret;
     struct stat mapstat;

     /* align shmsize to next power of 2 */
     shmsize = pow2ceil(shmsize);

     if (fstat(fd, &mapstat) != -1 && mapstat.st_size == shmsize) {
         return 0;
     }

     while (shmsize <= IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE) {
         ret = ftruncate(fd, shmsize);
         if (ret == 0) {
             return ret;
         }
         shmsize *= 2;
     }

     return -1;
 }

 /* Init a new ivshmem server */
 int
 ivshmem_server_init(IvshmemServer *server, const char *unix_sock_path,
                     const char *shm_path, bool use_shm_open,
                     size_t shm_size, unsigned n_vectors,
                     bool verbose)
 {
     int ret;

     memset(server, 0, sizeof(*server));
     server->verbose = verbose;

     ret = snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
                    "%s", unix_sock_path);
     if (ret < 0 || ret >= sizeof(server->unix_sock_path)) {
         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
         return -1;
     }
     ret = snprintf(server->shm_path, sizeof(server->shm_path),
                    "%s", shm_path);
     if (ret < 0 || ret >= sizeof(server->shm_path)) {
         IVSHMEM_SERVER_DEBUG(server, "could not copy shm path\n");
         return -1;
     }

     server->use_shm_open = use_shm_open;
     server->shm_size = shm_size;
     server->n_vectors = n_vectors;

     QTAILQ_INIT(&server->peer_list);

     return 0;
 }

 /* open shm, create and bind to the unix socket */
 int
 ivshmem_server_start(IvshmemServer *server)
 {
     struct sockaddr_un s_un;
     int shm_fd, sock_fd, ret;

     /* open shm file */
     if (server->use_shm_open) {
         IVSHMEM_SERVER_DEBUG(server, "Using POSIX shared memory: %s\n",
                              server->shm_path);
         shm_fd = shm_open(server->shm_path, O_CREAT | O_RDWR, S_IRWXU);
     } else {
         gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
         IVSHMEM_SERVER_DEBUG(server, "Using file-backed shared memory: %s\n",
                              server->shm_path);
         shm_fd = mkstemp(filename);
         unlink(filename);
         g_free(filename);
     }

     if (shm_fd < 0) {
         fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
                 strerror(errno));
         return -1;
     }
     if (ivshmem_server_ftruncate(shm_fd, server->shm_size) < 0) {
         fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
                 strerror(errno));
         goto err_close_shm;
     }

     IVSHMEM_SERVER_DEBUG(server, "create & bind socket %s\n",
                          server->unix_sock_path);

     /* create the unix listening socket */
     sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
     if (sock_fd < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot create socket: %s\n",
                              strerror(errno));
         goto err_close_shm;
     }

     s_un.sun_family = AF_UNIX;
     ret = snprintf(s_un.sun_path, sizeof(s_un.sun_path), "%s",
                    server->unix_sock_path);
     if (ret < 0 || ret >= sizeof(s_un.sun_path)) {
         IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
         goto err_close_sock;
     }
     if (bind(sock_fd, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
         IVSHMEM_SERVER_DEBUG(server, "cannot connect to %s: %s\n", s_un.sun_path,
                              strerror(errno));
         goto err_close_sock;
     }

     if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
         IVSHMEM_SERVER_DEBUG(server, "listen() failed: %s\n", strerror(errno));
         goto err_close_sock;
     }

     server->sock_fd = sock_fd;
     server->shm_fd = shm_fd;

     return 0;

 err_close_sock:
     close(sock_fd);
 err_close_shm:
     if (server->use_shm_open) {
         shm_unlink(server->shm_path);
     }
     close(shm_fd);
     return -1;
 }

 /* close connections to clients, the unix socket and the shm fd */
 void
 ivshmem_server_close(IvshmemServer *server)
 {
     IvshmemServerPeer *peer, *npeer;

     IVSHMEM_SERVER_DEBUG(server, "close server\n");

     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, npeer) {
         ivshmem_server_free_peer(server, peer);
     }

     unlink(server->unix_sock_path);
     if (server->use_shm_open) {
         shm_unlink(server->shm_path);
     }
     close(server->sock_fd);
     close(server->shm_fd);
     server->sock_fd = -1;
     server->shm_fd = -1;
 }

 /* get the fd_set according to the unix socket and the peer list */
 void
 ivshmem_server_get_fds(const IvshmemServer *server, fd_set *fds, int *maxfd)
 {
     IvshmemServerPeer *peer;

     if (server->sock_fd == -1) {
         return;
     }

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

     QTAILQ_FOREACH(peer, &server->peer_list, next) {
         FD_SET(peer->sock_fd, fds);
         if (peer->sock_fd >= *maxfd) {
             *maxfd = peer->sock_fd + 1;
         }
     }
 }

 /* process incoming messages on the sockets in fd_set */
 int
 ivshmem_server_handle_fds(IvshmemServer *server, fd_set *fds, int maxfd)
 {
     IvshmemServerPeer *peer, *peer_next;

     if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
         ivshmem_server_handle_new_conn(server) < 0 && errno != EINTR) {
         IVSHMEM_SERVER_DEBUG(server, "ivshmem_server_handle_new_conn() "
                              "failed\n");
         return -1;
     }

     QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, peer_next) {
         /* any message from a peer socket result in a close() */
         IVSHMEM_SERVER_DEBUG(server, "peer->sock_fd=%d\n", peer->sock_fd);
         if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
             ivshmem_server_free_peer(server, peer);
         }
     }

     return 0;
 }

 /* lookup peer from its id */
 IvshmemServerPeer *
 ivshmem_server_search_peer(IvshmemServer *server, int64_t peer_id)
 {
     IvshmemServerPeer *peer;

     QTAILQ_FOREACH(peer, &server->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_server_dump(const IvshmemServer *server)
 {
     const IvshmemServerPeer *peer;
     unsigned vector;

     /* dump peers */
     QTAILQ_FOREACH(peer, &server->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,
                    event_notifier_get_fd(&peer->vectors[vector]));
         }
     }
 }
	/*
	* 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 "qemu/host-utils.h"
	#include "qemu/sockets.h"

	#include <sys/socket.h>
	#include <sys/un.h>

	#include "ivshmem-server.h"

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

	/** maximum size of a huge page, used by ivshmem_server_ftruncate() */
	#define IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE (1024 * 1024 * 1024)

	/** default listen backlog (number of sockets not accepted) */
	#define IVSHMEM_SERVER_LISTEN_BACKLOG 10

	/* send message to a client unix socket */
	static int
	ivshmem_server_send_one_msg(int sock_fd, int64_t peer_id, 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;

	peer_id = GINT64_TO_LE(peer_id);
	iov[0].iov_base = &peer_id;
	iov[0].iov_len = sizeof(peer_id);

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

	/* if fd is specified, add it in a cmsg */
	if (fd >= 0) {
	memset(&msg_control, 0, sizeof(msg_control));
	msg.msg_control = &msg_control;
	msg.msg_controllen = sizeof(msg_control);
	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
	memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
	}

	ret = sendmsg(sock_fd, &msg, 0);
	if (ret <= 0) {
	return -1;
	}

	return 0;
	}

	/* free a peer when the server advertises a disconnection or when the
	* server is freed */
	static void
	ivshmem_server_free_peer(IvshmemServer server, IvshmemServerPeer peer)
	{
	unsigned vector;
	IvshmemServerPeer *other_peer;

	IVSHMEM_SERVER_DEBUG(server, "free peer %" PRId64 "\n", peer->id);
	close(peer->sock_fd);
	QTAILQ_REMOVE(&server->peer_list, peer, next);

	/* advertise the deletion to other peers */
	QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
	ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id, -1);
	}

	for (vector = 0; vector < peer->vectors_count; vector++) {
	event_notifier_cleanup(&peer->vectors[vector]);
	}

	g_free(peer);
	}

	/* send the peer id and the shm_fd just after a new client connection */
	static int
	ivshmem_server_send_initial_info(IvshmemServer server, IvshmemServerPeer peer)
	{
	int ret;

	/* send our protocol version first */
	ret = ivshmem_server_send_one_msg(peer->sock_fd, IVSHMEM_PROTOCOL_VERSION,
	-1);
	if (ret < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot send version: %s\n",
	strerror(errno));
	return -1;
	}

	/* send the peer id to the client */
	ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);
	if (ret < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot send peer id: %s\n",
	strerror(errno));
	return -1;
	}

	/* send the shm_fd */
	ret = ivshmem_server_send_one_msg(peer->sock_fd, -1, server->shm_fd);
	if (ret < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot send shm fd: %s\n",
	strerror(errno));
	return -1;
	}

	return 0;
	}

	/* handle message on listening unix socket (new client connection) */
	static int
	ivshmem_server_handle_new_conn(IvshmemServer *server)
	{
	IvshmemServerPeer peer, other_peer;
	struct sockaddr_un unaddr;
	socklen_t unaddr_len;
	int newfd;
	unsigned i;

	/* accept the incoming connection */
	unaddr_len = sizeof(unaddr);
	newfd = qemu_accept(server->sock_fd,
	(struct sockaddr *)&unaddr, &unaddr_len);

	if (newfd < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot accept() %s\n", strerror(errno));
	return -1;
	}

	qemu_socket_set_nonblock(newfd);
	IVSHMEM_SERVER_DEBUG(server, "accept()=%d\n", newfd);

	/* allocate new structure for this peer */
	peer = g_malloc0(sizeof(*peer));
	peer->sock_fd = newfd;

	/* get an unused peer id */
	/* XXX: this could use id allocation such as Linux IDA, or simply
	* a free-list */
	for (i = 0; i < G_MAXUINT16; i++) {
	if (ivshmem_server_search_peer(server, server->cur_id) == NULL) {
	break;
	}
	server->cur_id++;
	}
	if (i == G_MAXUINT16) {
	IVSHMEM_SERVER_DEBUG(server, "cannot allocate new client id\n");
	close(newfd);
	g_free(peer);
	return -1;
	}
	peer->id = server->cur_id++;

	/* create eventfd, one per vector */
	peer->vectors_count = server->n_vectors;
	for (i = 0; i < peer->vectors_count; i++) {
	if (event_notifier_init(&peer->vectors[i], FALSE) < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot create eventfd\n");
	goto fail;
	}
	}

	/* send peer id and shm fd */
	if (ivshmem_server_send_initial_info(server, peer) < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot send initial info\n");
	goto fail;
	}

	/* advertise the new peer to others */
	QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
	for (i = 0; i < peer->vectors_count; i++) {
	ivshmem_server_send_one_msg(other_peer->sock_fd, peer->id,
	peer->vectors[i].wfd);
	}
	}

	/* advertise the other peers to the new one */
	QTAILQ_FOREACH(other_peer, &server->peer_list, next) {
	for (i = 0; i < peer->vectors_count; i++) {
	ivshmem_server_send_one_msg(peer->sock_fd, other_peer->id,
	other_peer->vectors[i].wfd);
	}
	}

	/* advertise the new peer to itself */
	for (i = 0; i < peer->vectors_count; i++) {
	ivshmem_server_send_one_msg(peer->sock_fd, peer->id,
	event_notifier_get_fd(&peer->vectors[i]));
	}

	QTAILQ_INSERT_TAIL(&server->peer_list, peer, next);
	IVSHMEM_SERVER_DEBUG(server, "new peer id = %" PRId64 "\n",
	peer->id);
	return 0;

	fail:
	while (i--) {
	event_notifier_cleanup(&peer->vectors[i]);
	}
	close(newfd);
	g_free(peer);
	return -1;
	}

	/* Try to ftruncate a file to next power of 2 of shmsize.
	* If it fails; all power of 2 above shmsize are tested until
	* we reach the maximum huge page size. This is useful
	* if the shm file is in a hugetlbfs that cannot be truncated to the
	* shm_size value. */
	static int
	ivshmem_server_ftruncate(int fd, unsigned shmsize)
	{
	int ret;
	struct stat mapstat;

	/* align shmsize to next power of 2 */
	shmsize = pow2ceil(shmsize);

	if (fstat(fd, &mapstat) != -1 && mapstat.st_size == shmsize) {
	return 0;
	}

	while (shmsize <= IVSHMEM_SERVER_MAX_HUGEPAGE_SIZE) {
	ret = ftruncate(fd, shmsize);
	if (ret == 0) {
	return ret;
	}
	shmsize *= 2;
	}

	return -1;
	}

	/* Init a new ivshmem server */
	int
	ivshmem_server_init(IvshmemServer server, const char unix_sock_path,
	const char *shm_path, bool use_shm_open,
	size_t shm_size, unsigned n_vectors,
	bool verbose)
	{
	int ret;

	memset(server, 0, sizeof(*server));
	server->verbose = verbose;

	ret = snprintf(server->unix_sock_path, sizeof(server->unix_sock_path),
	"%s", unix_sock_path);
	if (ret < 0 \|\| ret >= sizeof(server->unix_sock_path)) {
	IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
	return -1;
	}
	ret = snprintf(server->shm_path, sizeof(server->shm_path),
	"%s", shm_path);
	if (ret < 0 \|\| ret >= sizeof(server->shm_path)) {
	IVSHMEM_SERVER_DEBUG(server, "could not copy shm path\n");
	return -1;
	}

	server->use_shm_open = use_shm_open;
	server->shm_size = shm_size;
	server->n_vectors = n_vectors;

	QTAILQ_INIT(&server->peer_list);

	return 0;
	}

	/* open shm, create and bind to the unix socket */
	int
	ivshmem_server_start(IvshmemServer *server)
	{
	struct sockaddr_un s_un;
	int shm_fd, sock_fd, ret;

	/* open shm file */
	if (server->use_shm_open) {
	IVSHMEM_SERVER_DEBUG(server, "Using POSIX shared memory: %s\n",
	server->shm_path);
	shm_fd = shm_open(server->shm_path, O_CREAT \| O_RDWR, S_IRWXU);
	} else {
	gchar *filename = g_strdup_printf("%s/ivshmem.XXXXXX", server->shm_path);
	IVSHMEM_SERVER_DEBUG(server, "Using file-backed shared memory: %s\n",
	server->shm_path);
	shm_fd = mkstemp(filename);
	unlink(filename);
	g_free(filename);
	}

	if (shm_fd < 0) {
	fprintf(stderr, "cannot open shm file %s: %s\n", server->shm_path,
	strerror(errno));
	return -1;
	}
	if (ivshmem_server_ftruncate(shm_fd, server->shm_size) < 0) {
	fprintf(stderr, "ftruncate(%s) failed: %s\n", server->shm_path,
	strerror(errno));
	goto err_close_shm;
	}

	IVSHMEM_SERVER_DEBUG(server, "create & bind socket %s\n",
	server->unix_sock_path);

	/* create the unix listening socket */
	sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock_fd < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot create socket: %s\n",
	strerror(errno));
	goto err_close_shm;
	}

	s_un.sun_family = AF_UNIX;
	ret = snprintf(s_un.sun_path, sizeof(s_un.sun_path), "%s",
	server->unix_sock_path);
	if (ret < 0 \|\| ret >= sizeof(s_un.sun_path)) {
	IVSHMEM_SERVER_DEBUG(server, "could not copy unix socket path\n");
	goto err_close_sock;
	}
	if (bind(sock_fd, (struct sockaddr *)&s_un, sizeof(s_un)) < 0) {
	IVSHMEM_SERVER_DEBUG(server, "cannot connect to %s: %s\n", s_un.sun_path,
	strerror(errno));
	goto err_close_sock;
	}

	if (listen(sock_fd, IVSHMEM_SERVER_LISTEN_BACKLOG) < 0) {
	IVSHMEM_SERVER_DEBUG(server, "listen() failed: %s\n", strerror(errno));
	goto err_close_sock;
	}

	server->sock_fd = sock_fd;
	server->shm_fd = shm_fd;

	return 0;

	err_close_sock:
	close(sock_fd);
	err_close_shm:
	if (server->use_shm_open) {
	shm_unlink(server->shm_path);
	}
	close(shm_fd);
	return -1;
	}

	/* close connections to clients, the unix socket and the shm fd */
	void
	ivshmem_server_close(IvshmemServer *server)
	{
	IvshmemServerPeer peer, npeer;

	IVSHMEM_SERVER_DEBUG(server, "close server\n");

	QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, npeer) {
	ivshmem_server_free_peer(server, peer);
	}

	unlink(server->unix_sock_path);
	if (server->use_shm_open) {
	shm_unlink(server->shm_path);
	}
	close(server->sock_fd);
	close(server->shm_fd);
	server->sock_fd = -1;
	server->shm_fd = -1;
	}

	/* get the fd_set according to the unix socket and the peer list */
	void
	ivshmem_server_get_fds(const IvshmemServer server, fd_set fds, int *maxfd)
	{
	IvshmemServerPeer *peer;

	if (server->sock_fd == -1) {
	return;
	}

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

	QTAILQ_FOREACH(peer, &server->peer_list, next) {
	FD_SET(peer->sock_fd, fds);
	if (peer->sock_fd >= *maxfd) {
	*maxfd = peer->sock_fd + 1;
	}
	}
	}

	/* process incoming messages on the sockets in fd_set */
	int
	ivshmem_server_handle_fds(IvshmemServer server, fd_set fds, int maxfd)
	{
	IvshmemServerPeer peer, peer_next;

	if (server->sock_fd < maxfd && FD_ISSET(server->sock_fd, fds) &&
	ivshmem_server_handle_new_conn(server) < 0 && errno != EINTR) {
	IVSHMEM_SERVER_DEBUG(server, "ivshmem_server_handle_new_conn() "
	"failed\n");
	return -1;
	}

	QTAILQ_FOREACH_SAFE(peer, &server->peer_list, next, peer_next) {
	/* any message from a peer socket result in a close() */
	IVSHMEM_SERVER_DEBUG(server, "peer->sock_fd=%d\n", peer->sock_fd);
	if (peer->sock_fd < maxfd && FD_ISSET(peer->sock_fd, fds)) {
	ivshmem_server_free_peer(server, peer);
	}
	}

	return 0;
	}

	/* lookup peer from its id */
	IvshmemServerPeer *
	ivshmem_server_search_peer(IvshmemServer *server, int64_t peer_id)
	{
	IvshmemServerPeer *peer;

	QTAILQ_FOREACH(peer, &server->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_server_dump(const IvshmemServer *server)
	{
	const IvshmemServerPeer *peer;
	unsigned vector;

	/* dump peers */
	QTAILQ_FOREACH(peer, &server->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,
	event_notifier_get_fd(&peer->vectors[vector]));
	}
	}
	}