[PATCH] migration: Apply migration specific keep-alive defaults to inet socket

[Juraj Marcin <jmarcin@redhat.com>]

From: Juraj Marcin <jmarcin@redhat.com>

Usual system defaults for TCP keep-alive options are too long for
migration workload. On Linux, a TCP connection waits idle for 2 hours
before it starts checking if the connection is not broken.

Now when InetSocketAddress supports keep-alive options [1], this patch
applies migration specific defaults if they are not supplied by the user
or the management software. With these defaults, a migration TCP stream
waits idle for 1 minute and then sends 5 TCP keep-alive packets in 30
second interval before considering the connection as broken.

System defaults can be still used by explicitly setting these parameters
to 0.

[1]: 1bd4237cb1 "util/qemu-sockets: Introduce inet socket options
     controlling TCP keep-alive"

Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
---
 migration/migration.c | 39 +++++++++++++++++++++++++++++++++++++++
 qapi/migration.json   |  6 ++++++
 2 files changed, 45 insertions(+)

diff --git a/migration/migration.c b/migration/migration.c
index 10c216d25d..a1f1223946 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -74,6 +74,11 @@
 
 #define INMIGRATE_DEFAULT_EXIT_ON_ERROR true
 
+#define INET_SOCKET_DEFAULT_KEEP_ALIVE true
+#define INET_SOCKET_DEFAULT_KEEP_ALIVE_COUNT 5
+#define INET_SOCKET_DEFAULT_KEEP_ALIVE_IDLE 60
+#define INET_SOCKET_DEFAULT_KEEP_ALIVE_INTERVAL 30
+
 static NotifierWithReturnList migration_state_notifiers[] = {
     NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_NORMAL),
     NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_REBOOT),
@@ -718,6 +723,36 @@ bool migrate_uri_parse(const char *uri, MigrationChannel **channel,
     return true;
 }
 
+static void migration_address_apply_defaults(MigrationAddress *addr)
+{
+    if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET &&
+        addr->u.socket.type == SOCKET_ADDRESS_TYPE_INET) {
+        InetSocketAddress *inet = &addr->u.socket.u.inet;
+        if (!inet->has_keep_alive) {
+            inet->has_keep_alive = true;
+            inet->keep_alive = INET_SOCKET_DEFAULT_KEEP_ALIVE;
+        }
+#ifdef HAVE_TCP_KEEPCNT
+        if (!inet->has_keep_alive_count) {
+            inet->has_keep_alive_count = true;
+            inet->keep_alive_count = INET_SOCKET_DEFAULT_KEEP_ALIVE_COUNT;
+        }
+#endif
+#ifdef HAVE_TCP_KEEPIDLE
+        if (!inet->has_keep_alive_idle) {
+            inet->has_keep_alive_idle = true;
+            inet->keep_alive_idle = INET_SOCKET_DEFAULT_KEEP_ALIVE_IDLE;
+        }
+#endif
+#ifdef HAVE_TCP_KEEPINTVL
+        if (!inet->has_keep_alive_interval) {
+            inet->has_keep_alive_interval = true;
+            inet->keep_alive_interval = INET_SOCKET_DEFAULT_KEEP_ALIVE_INTERVAL;
+        }
+#endif
+    }
+}
+
 static bool
 migration_incoming_state_setup(MigrationIncomingState *mis, Error **errp)
 {
@@ -775,6 +810,8 @@ static void qemu_start_incoming_migration(const char *uri, bool has_channels,
         addr = channel->addr;
     }
 
+    migration_address_apply_defaults(addr);
+
     /* transport mechanism not suitable for migration? */
     if (!migration_transport_compatible(addr, errp)) {
         return;
@@ -2232,6 +2269,8 @@ void qmp_migrate(const char *uri, bool has_channels,
         addr = channel->addr;
     }
 
+    migration_address_apply_defaults(addr);
+
     /* transport mechanism not suitable for migration? */
     if (!migration_transport_compatible(addr, errp)) {
         return;
diff --git a/qapi/migration.json b/qapi/migration.json
index 2387c21e9c..68d4acb5db 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -1639,6 +1639,12 @@
 #
 # Migration endpoint configuration.
 #
+# If transport is socket of type inet, it has the following defaults:
+# keep-alive: true, keep-alive-count: 5, keep-alive-idle: 60 seconds,
+# keep-alive-interval: 30 seconds.  System defaults can be used by
+# explicitly setting these parameters to 0.  See `InetSocketAddress` for
+# more details.
+#
 # @transport: The migration stream transport mechanism
 #
 # Since: 8.2
-- 
2.51.0