[CRIU] [PATCH] tcp: allow to repair the FIN_WAIT2 state

[Andrey Vagin]

A socket in the FIN_WAIT2 state doesn't have unacknowledged data in a
queue. We don't need to send anything back and can restore it directly.

This state allows us to restore socket in the TIME_WAIT state. For that
we need to set the FIN_WAIT2 state and send the fin packet in a received
queue.

Signed-off-by: Andrey Vagin <avagin at openvz.org>
---
 include/uapi/linux/tcp.h |  1 +
 net/ipv4/tcp.c           | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index b1d5973..d9f7970 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -201,5 +201,6 @@ struct tcp_md5sig {
 
 /* Control message types to repair tcp connections */
 #define TCP_REPAIR_SEND_FIN	1
+#define TCP_REPAIR_FIN_WAIT2	2
 
 #endif /* _UAPI_LINUX_TCP_H */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d196598..5345980 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1090,6 +1090,16 @@ static int tcp_repair_cmsg(struct sock *sk, struct msghdr *msg)
 			else
 				return -EINVAL;
 			break;
+
+		case TCP_REPAIR_FIN_WAIT2:
+			if (tp->repair_queue != TCP_SEND_QUEUE ||
+			    sk->sk_state != TCP_ESTABLISHED ||
+			    tp->snd_una != tp->write_seq)
+				return -EINVAL;
+
+			tcp_set_state(sk, TCP_FIN_WAIT2);
+
+			break;
 		default:
 			return -EINVAL;
 		}
-- 
1.8.5.3