contrib: add ivshmem client and server

When using ivshmem devices, notifications between guests can be sent as
interrupts using a ivshmem-server (typical use described in documentation).
The client is provided as a debug tool.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: David Marchand <david.marchand@6wind.com>
[fix a valgrind warning, option and server_close() segvs, extra server
headers includes, getopt() return type, out-of-tree build, use qemu
event_notifier instead of eventfd, fix x86/osx warnings - Marc-André]
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

contrib/ivshmem-client/ivshmem-client.h

@@ -0,0 +1,212 @@
+/*
+ * 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.
+ */
+
+#ifndef _IVSHMEM_CLIENT_H_
+#define _IVSHMEM_CLIENT_H_
+
+/**
+ * This file provides helper to implement an ivshmem client. It is used
+ * on the host to ask QEMU to send an interrupt to an ivshmem PCI device in a
+ * guest. QEMU also implements an ivshmem client similar to this one, they both
+ * connect to an ivshmem server.
+ *
+ * A standalone ivshmem client based on this file is provided for debug/test
+ * purposes.
+ */
+
+#include <limits.h>
+#include <sys/select.h>
+
+#include "qemu/queue.h"
+
+/**
+ * Maximum number of notification vectors supported by the client
+ */
+#define IVSHMEM_CLIENT_MAX_VECTORS 64
+
+/**
+ * Structure storing a peer
+ *
+ * Each time a client connects to an ivshmem server, it is advertised to
+ * all connected clients through the unix socket. When our ivshmem
+ * client receives a notification, it creates a IvshmemClientPeer
+ * structure to store the infos of this peer.
+ *
+ * This structure is also used to store the information of our own
+ * client in (IvshmemClient)->local.
+ */
+typedef struct IvshmemClientPeer {
+    QTAILQ_ENTRY(IvshmemClientPeer) next;    /**< next in list*/
+    long id;                                 /**< the id of the peer */
+    int vectors[IVSHMEM_CLIENT_MAX_VECTORS]; /**< one fd per vector */
+    unsigned vectors_count;                  /**< number of vectors */
+} IvshmemClientPeer;
+QTAILQ_HEAD(IvshmemClientPeerList, IvshmemClientPeer);
+
+typedef struct IvshmemClientPeerList IvshmemClientPeerList;
+typedef struct IvshmemClient IvshmemClient;
+
+/**
+ * Typedef of callback function used when our IvshmemClient receives a
+ * notification from a peer.
+ */
+typedef void (*IvshmemClientNotifCb)(
+    const IvshmemClient *client,
+    const IvshmemClientPeer *peer,
+    unsigned vect, void *arg);
+
+/**
+ * Structure describing an ivshmem client
+ *
+ * This structure stores all information related to our client: the name
+ * of the server unix socket, the list of peers advertised by the
+ * server, our own client information, and a pointer the notification
+ * callback function used when we receive a notification from a peer.
+ */
+struct IvshmemClient {
+    char unix_sock_path[PATH_MAX];      /**< path to unix sock */
+    int sock_fd;                        /**< unix sock filedesc */
+    int shm_fd;                         /**< shm file descriptor */
+
+    IvshmemClientPeerList peer_list;    /**< list of peers */
+    IvshmemClientPeer local;            /**< our own infos */
+
+    IvshmemClientNotifCb notif_cb;      /**< notification callback */
+    void *notif_arg;                    /**< notification argument */
+
+    bool verbose;                       /**< true to enable debug */
+};
+
+/**
+ * Initialize an ivshmem client
+ *
+ * @client:         A pointer to an uninitialized IvshmemClient structure
+ * @unix_sock_path: The pointer to the unix socket file name
+ * @notif_cb:       If not NULL, the pointer to the function to be called when
+ *                  our IvshmemClient receives a notification from a peer
+ * @notif_arg:      Opaque pointer given as-is to the notification callback
+ *                  function
+ * @verbose:        True to enable debug
+ *
+ * Returns:         0 on success, or a negative value on error
+ */
+int ivshmem_client_init(IvshmemClient *client, const char *unix_sock_path,
+                        IvshmemClientNotifCb notif_cb, void *notif_arg,
+                        bool verbose);
+
+/**
+ * Connect to the server
+ *
+ * Connect to the server unix socket, and read the first initial
+ * messages sent by the server, giving the ID of the client and the file
+ * descriptor of the shared memory.
+ *
+ * @client: The ivshmem client
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_connect(IvshmemClient *client);
+
+/**
+ * Close connection to the server and free all peer structures
+ *
+ * @client: The ivshmem client
+ */
+void ivshmem_client_close(IvshmemClient *client);
+
+/**
+ * Fill a fd_set with file descriptors to be monitored
+ *
+ * This function will fill a fd_set with all file descriptors
+ * that must be polled (unix server socket and peers eventfd). The
+ * function will not initialize the fd_set, it is up to the caller
+ * to do this.
+ *
+ * @client: The ivshmem client
+ * @fds:    The fd_set to be updated
+ * @maxfd:  Must be set to the max file descriptor + 1 in fd_set. This value is
+ *          updated if this function adds a greater fd in fd_set.
+ */
+void ivshmem_client_get_fds(const IvshmemClient *client, fd_set *fds,
+                            int *maxfd);
+
+/**
+ * Read and handle new messages
+ *
+ * Given a fd_set filled by select(), handle incoming messages from
+ * server or peers.
+ *
+ * @client: The ivshmem client
+ * @fds:    The fd_set containing the file descriptors to be checked. Note
+ *          that file descriptors that are not related to our client are
+ *          ignored.
+ * @maxfd:  The maximum fd in fd_set, plus one.
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_handle_fds(IvshmemClient *client, fd_set *fds, int maxfd);
+
+/**
+ * Send a notification to a vector of a peer
+ *
+ * @client: The ivshmem client
+ * @peer:   The peer to be notified
+ * @vector: The number of the vector
+ *
+ * Returns: 0 on success, or a negative value on error
+ */
+int ivshmem_client_notify(const IvshmemClient *client,
+                          const IvshmemClientPeer *peer, unsigned vector);
+
+/**
+ * Send a notification to all vectors of a peer
+ *
+ * @client: The ivshmem client
+ * @peer:   The peer to be notified
+ *
+ * Returns: 0 on success, or a negative value on error (at least one
+ *          notification failed)
+ */
+int ivshmem_client_notify_all_vects(const IvshmemClient *client,
+                                    const IvshmemClientPeer *peer);
+
+/**
+ * Broadcat a notification to all vectors of all peers
+ *
+ * @client: The ivshmem client
+ *
+ * Returns: 0 on success, or a negative value on error (at least one
+ *          notification failed)
+ */
+int ivshmem_client_notify_broadcast(const IvshmemClient *client);
+
+/**
+ * Search a peer from its identifier
+ *
+ * Return the peer structure from its peer_id. If the given peer_id is
+ * the local id, the function returns the local peer structure.
+ *
+ * @client:  The ivshmem client
+ * @peer_id: The identifier of the peer structure
+ *
+ * Returns:  The peer structure, or NULL if not found
+ */
+IvshmemClientPeer *
+ivshmem_client_search_peer(IvshmemClient *client, long peer_id);
+
+/**
+ * Dump information of this ivshmem client on stdout
+ *
+ * Dump the id and the vectors of the given ivshmem client and the list
+ * of its peers and their vectors on stdout.
+ *
+ * @client: The ivshmem client
+ */
+void ivshmem_client_dump(const IvshmemClient *client);
+
+#endif /* _IVSHMEM_CLIENT_H_ */