SUNRPC: fix shutdown of NFS TCP client socket

Siddharth Kawar · amschuma-ntap · commit 943d045a6d79 · 2023-03-23T15:50:16.000-04:00
NFS server Duplicate Request Cache (DRC) algorithms rely on NFS clients reconnecting using the same local TCP port. Unique NFS operations are identified by the per-TCP connection set of XIDs. This prevents file corruption when non-idempotent NFS operations are retried. Currently, NFS client TCP connections are using different local TCP ports when reconnecting to NFS servers. After an NFS server initiates shutdown of the TCP connection, the NFS client's TCP socket is set to NULL after the socket state has reached TCP_LAST_ACK(9). When reconnecting, the new socket attempts to reuse the same local port but fails with EADDRNOTAVAIL (99). This forces the socket to use a different local TCP port to reconnect to the remote NFS server. State Transition and Events: TCP_CLOSE_WAIT(8) TCP_LAST_ACK(9) connect(fail EADDRNOTAVAIL(99)) TCP_CLOSE(7) bind on new port connect success dmesg excerpts showing reconnect switching from TCP local port of 926 to 763 after commit 7c81e6a: [13354.947854] NFS call mkdir testW ... [13405.654781] RPC: xs_tcp_state_change client 00000000037d0f03... [13405.654813] RPC: state 8 conn 1 dead 0 zapped 1 sk_shutdown 1 [13405.654826] RPC: xs_data_ready... [13405.654892] RPC: xs_tcp_state_change client 00000000037d0f03... [13405.654895] RPC: state 9 conn 0 dead 0 zapped 1 sk_shutdown 3 [13405.654899] RPC: xs_tcp_state_change client 00000000037d0f03... [13405.654900] RPC: state 9 conn 0 dead 0 zapped 1 sk_shutdown 3 [13405.654950] RPC: xs_connect scheduled xprt 00000000037d0f03 [13405.654975] RPC: xs_bind 0.0.0.0:926: ok (0) [13405.654980] RPC: worker connecting xprt 00000000037d0f03 via tcp to 10.101.6.228 (port 2049) [13405.654991] RPC: 00000000037d0f03 connect status 99 connected 0 sock state 7 [13405.655001] RPC: xs_tcp_state_change client 00000000037d0f03... [13405.655002] RPC: state 7 conn 0 dead 0 zapped 1 sk_shutdown 3 [13405.655024] RPC: xs_connect scheduled xprt 00000000037d0f03 [13405.655038] RPC: xs_bind 0.0.0.0:763: ok (0) [13405.655041] RPC: worker connecting xprt 00000000037d0f03 via tcp to 10.101.6.228 (port 2049) [13405.655065] RPC: 00000000037d0f03 connect status 115 connected 0 sock state 2 State Transition and Events with patch applied: TCP_CLOSE_WAIT(8) TCP_LAST_ACK(9) TCP_CLOSE(7) connect(reuse of port succeeds) dmesg excerpts showing reconnect on same TCP local port of 936 with patch applied: [ 257.139935] NFS: mkdir(0:59/560857152), testQ [ 257.139937] NFS call mkdir testQ ... [ 307.822702] RPC: state 8 conn 1 dead 0 zapped 1 sk_shutdown 1 [ 307.822714] RPC: xs_data_ready... [ 307.822817] RPC: xs_tcp_state_change client 00000000ce702f14... [ 307.822821] RPC: state 9 conn 0 dead 0 zapped 1 sk_shutdown 3 [ 307.822825] RPC: xs_tcp_state_change client 00000000ce702f14... [ 307.822826] RPC: state 9 conn 0 dead 0 zapped 1 sk_shutdown 3 [ 307.823606] RPC: xs_tcp_state_change client 00000000ce702f14... [ 307.823609] RPC: state 7 conn 0 dead 0 zapped 1 sk_shutdown 3 [ 307.823629] RPC: xs_tcp_state_change client 00000000ce702f14... [ 307.823632] RPC: state 7 conn 0 dead 0 zapped 1 sk_shutdown 3 [ 307.823676] RPC: xs_connect scheduled xprt 00000000ce702f14 [ 307.823704] RPC: xs_bind 0.0.0.0:936: ok (0) [ 307.823709] RPC: worker connecting xprt 00000000ce702f14 via tcp to 10.101.1.30 (port 2049) [ 307.823748] RPC: 00000000ce702f14 connect status 115 connected 0 sock state 2 ... [ 314.916193] RPC: state 7 conn 0 dead 0 zapped 1 sk_shutdown 3 [ 314.916251] RPC: xs_connect scheduled xprt 00000000ce702f14 [ 314.916282] RPC: xs_bind 0.0.0.0:936: ok (0) [ 314.916292] RPC: worker connecting xprt 00000000ce702f14 via tcp to 10.101.1.30 (port 2049) [ 314.916342] RPC: 00000000ce702f14 connect status 115 connected 0 sock state 2 Fixes: 7c81e6a ("SUNRPC: Tweak TCP socket shutdown in the RPC client") Signed-off-by: Siddharth Rajendra Kawar <sikawar@microsoft.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
@@ -2158,6 +2158,7 @@ static void xs_tcp_shutdown(struct rpc_xprt *xprt)
 	switch (skst) {
 	case TCP_FIN_WAIT1:
 	case TCP_FIN_WAIT2:
+	case TCP_LAST_ACK:
 		break;
 	case TCP_ESTABLISHED:
 	case TCP_CLOSE_WAIT:
