[PATCH 5 of 9 RFC v2] blktap3/libblktapctl: Introduce functionality used by tapback to instruct tapdisk to connect to the sring

[Thanos Makatos <thanos.makatos@citrix.com>]

This patch introduces functions tap_ctl_connect_xenblkif and
tap_ctl_disconnect_xenblkif, that are used by the tapback daemon to instruct a
running tapdisk process to connect to/disconnect from the shared ring.

diff --git a/tools/blktap3/control/tap-ctl-xen.c b/tools/blktap3/control/tap-ctl-xen.c
new file mode 100644
--- /dev/null
+++ b/tools/blktap3/control/tap-ctl-xen.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2012      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+ * USA.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "tap-ctl.h"
+#include "tap-ctl-xen.h"
+
+int tap_ctl_connect_xenblkif(pid_t pid, int minor, domid_t domid,
+        int devid, const grant_ref_t * grefs, int order,
+        const evtchn_port_t port, int proto, const char *pool)
+{
+    tapdisk_message_t message;
+    int i, err;
+
+    memset(&message, 0, sizeof(message));
+    message.type = TAPDISK_MESSAGE_XENBLKIF_CONNECT;
+    message.cookie = minor;
+
+    message.u.blkif.domid = domid;
+    message.u.blkif.devid = devid;
+    for (i = 0; i < 1 << order; i++)
+        message.u.blkif.gref[i] = grefs[i];
+    message.u.blkif.order = order;
+    message.u.blkif.port = port;
+    message.u.blkif.proto = proto;
+    if (pool)
+        strncpy(message.u.blkif.pool, pool, sizeof(message.u.blkif.pool));
+    else
+        message.u.blkif.pool[0] = 0;
+
+    err = tap_ctl_connect_send_and_receive(pid, &message, NULL);
+    if (err)
+        return err;
+
+    if (message.type == TAPDISK_MESSAGE_XENBLKIF_CONNECT_RSP)
+        err = -message.u.response.error;
+    else
+        err = -EINVAL;
+
+    return err;
+}
+
+int tap_ctl_disconnect_xenblkif(pid_t pid, int minor, domid_t domid,
+        int devid, struct timeval *timeout)
+{
+    tapdisk_message_t message;
+    int err;
+
+    memset(&message, 0, sizeof(message));
+    message.type = TAPDISK_MESSAGE_XENBLKIF_DISCONNECT;
+    message.cookie = minor;
+    message.u.blkif.domid = domid;
+    message.u.blkif.devid = devid;
+
+    err = tap_ctl_connect_send_and_receive(pid, &message, timeout);
+    if (message.type == TAPDISK_MESSAGE_XENBLKIF_CONNECT_RSP)
+        err = -message.u.response.error;
+    else
+        err = -EINVAL;
+
+    return err;
+}
diff --git a/tools/blktap3/control/tap-ctl-xen.h b/tools/blktap3/control/tap-ctl-xen.h
new file mode 100644
--- /dev/null
+++ b/tools/blktap3/control/tap-ctl-xen.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2012      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+ * USA.
+ */
+
+#ifndef __TAP_CTL_XEN_H__
+#define __TAP_CTL_XEN_H__
+
+#include <xen/xen.h>
+#include <xen/grant_table.h>
+#include <xen/event_channel.h>
+
+/**
+ * Instructs a tapdisk to connect to the shared ring.
+ *
+ * TODO further explain parameters
+ *
+ * @param pid the process ID of the tapdisk that should connect to the shared
+ * ring
+ * @param minor the minor number of the virtual block device
+ * @param domid the domain ID of the guest VM
+ * @param devid the device ID
+ * @param grefs the grant references
+ * @param order number of grant references, expressed as a 2's order
+ * @param port event channel port
+ * @param proto the protocol: native (XENIO_BLKIF_PROTO_NATIVE),
+ * x86 (XENIO_BLKIF_PROTO_X86_32), or x64 (XENIO_BLKIF_PROTO_X86_64)
+ * @param pool TODO page pool?
+ * @returns 0 on success, an error code otherwise
+ */
+int tap_ctl_connect_xenblkif(pid_t pid, int minor, domid_t domid, int devid,
+        const grant_ref_t * grefs, int order, evtchn_port_t port, int proto,
+        const char *pool);
+
+/**
+ * Instructs a tapdisk to disconnect from the shared ring.
+ *
+ * @param pid the process ID of the tapdisk that should disconnect
+ * @param minor the minor number of the virtual block device
+ * @param domid the ID of the guest VM
+ * @param devid the device ID of the virtual block device
+ * @param timeout timeout to wait, if NULL the function will wait indefinitely
+ */
+int tap_ctl_disconnect_xenblkif(pid_t pid, int minor, domid_t domid,
+        int devid, struct timeval *timeout);
+
+#endif /* __TAP_CTL_XEN_H__ */