server/spice.h: semi-seamless migration interface, RHBZ #738266

semi-seamless migration details:

migration source side
---------------------
(1) spice_server_migrate_connect (*): tell client to link
    to the target side - send SPICE_MSG_MAIN_MIGRATE_BEGIN.
    This should be called upon client_migrate_info cmd.
    client_migrate_info is asynchronous.
(2) Complete spice_server_migrate_connect only when the client has been connected
    to the target - wait for SPICE_MSGC_MAIN_MIGRATE_(CONNECTED|CONNECT_ERROR) or a timeout.
(3) spice_server_migrate_end: tell client migration it can switch to the target - send
    SPICE_MSG_MAIN_MIGRATE_END.
(4) client cleans up all data related to the connection to the source and switches to the target.
    It sends SPICE_MSGC_MAIN_MIGRATE_END.

migration target side
---------------------
(1) the server identifies itself as a migraiton target since the client is linked with (connection_id != 0)
(2) server doesn't start the channels' logic (channel->link) till it receives SPICE_MSGC_MAIN_MIGRATE_END
    from the client.

*   After migration starts, the target qemu is blocked and cannot accept new spice client
    connections. Thus, we trigger the connection to the target upon client_migrate_info
    command.

3 files changed, 35 insertions, 4 deletions

diff --git a/server/reds.c b/server/reds.c
index f082c531..9a983f8c 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -4854,6 +4854,15 @@ SPICE_GNUC_VISIBLE int spice_server_set_agent_copypaste(SpiceServer *s, int enab
     return 0;
 }
 
+/* semi-seamless client migration */
+SPICE_GNUC_VISIBLE int spice_server_migrate_connect(SpiceServer *s, const char* dest,
+                                                    int port, int secure_port,
+                                                    const char* cert_subject)
+{
+    red_printf("not implemented yet");
+    return 0;
+}
+
 SPICE_GNUC_VISIBLE int spice_server_migrate_info(SpiceServer *s, const char* dest,
                                           int port, int secure_port,
                                           const char* cert_subject)
diff --git a/server/spice-experimental.h b/server/spice-experimental.h
index 482ac44b..6997aa03 100644
--- a/server/spice-experimental.h
+++ b/server/spice-experimental.h
@@ -29,16 +29,13 @@ void spice_server_net_wire_recv_packet(SpiceNetWireInstance *sin,
                                        const uint8_t *pkt, int len);
 
 /* spice seamless client migration (broken) */
-
 enum {
     SPICE_MIGRATE_CLIENT_NONE = 1,
     SPICE_MIGRATE_CLIENT_WAITING,
     SPICE_MIGRATE_CLIENT_READY,
 };
 
-int spice_server_migrate_start(SpiceServer *s);
 int spice_server_migrate_client_state(SpiceServer *s);
-int spice_server_migrate_end(SpiceServer *s, int completed);
 
 #endif // __SPICE_EXPERIMENTAL_H__
 
diff --git a/server/spice.h b/server/spice.h
index ac5a41eb..42ddbc64 100644
--- a/server/spice.h
+++ b/server/spice.h
@@ -469,11 +469,36 @@ int spice_server_set_agent_copypaste(SpiceServer *s, int enable);
 int spice_server_get_sock_info(SpiceServer *s, struct sockaddr *sa, socklen_t *salen);
 int spice_server_get_peer_info(SpiceServer *s, struct sockaddr *sa, socklen_t *salen);
 
-/* spice switch-host client migration */
+/* migration interface */
+#define SPICE_INTERFACE_MIGRATION "migration"
+#define SPICE_INTERFACE_MIGRATION_MAJOR 1
+#define SPICE_INTERFACE_MIGRATION_MINOR 1
+typedef struct SpiceMigrateInterface SpiceMigrateInterface;
+typedef struct SpiceMigrateInstance SpiceMigrateInstance;
+typedef struct SpiceMigrateState SpiceMigrateState;
+
+struct SpiceMigrateInterface {
+    SpiceBaseInterface base;
+    void (*migrate_connect_complete)(SpiceMigrateInstance *sin);
+    void (*migrate_end_complete)(SpiceMigrateInstance *sin);
+};
+
+struct SpiceMigrateInstance {
+    SpiceBaseInstance base;
+    SpiceMigrateState *st;
+};
 
+/* spice switch-host client migration */
 int spice_server_migrate_info(SpiceServer *s, const char* dest,
                               int port, int secure_port,
                               const char* cert_subject);
 int spice_server_migrate_switch(SpiceServer *s);
 
+/* spice (semi-)seamless client migration */
+int spice_server_migrate_connect(SpiceServer *s, const char* dest,
+                                 int port, int secure_port,
+                                 const char* cert_subject);
+int spice_server_migrate_start(SpiceServer *s);
+int spice_server_migrate_end(SpiceServer *s, int completed);
+
 #endif