DATA_FIN is not retransmitted on timeout

[pabeni]

currently we don't have any code in place to check for DATA_FIN timeout and retransmit.

[mjmartineau]

Request from @pabeni: Look at using delegated actions instead of workqueue

[matttbe]

Just to track the frequency, my CI just reported an issue where one socket is in FIN-WAIT-2:

# selftests: net/mptcp: mptcp_connect.sh
--
  | # INFO: set ns3-60559cc5-rBzcRI dev ns3eth2: ethtool -K tso off gso off gro off
  | # INFO: set ns4-60559cc5-rBzcRI dev ns4eth3: ethtool -K  gso off
  | # Created /tmp/tmp.K74Gvqcdyw (size 3849244	/tmp/tmp.K74Gvqcdyw) containing data sent by client
  | # Created /tmp/tmp.a5zdIoF5YL (size 172060	/tmp/tmp.a5zdIoF5YL) containing data sent by server
  | # New MPTCP socket can be blocked via sysctl		[ OK ]
  | # setsockopt(..., TCP_ULP, "mptcp", ...) blocked	[ OK ]
  | # INFO: validating network environment with pings
  | # INFO: Using loss of 0.74% delay 28 ms reorder 92% 81% with delay 7ms on ns3eth4
  | # ns1 MPTCP -> ns1 (10.0.1.1:10000      ) MPTCP	(duration    83ms) [ OK ]
  | # ns1 MPTCP -> ns1 (10.0.1.1:10001      ) TCP  	(duration    33ms) [ OK ]
  | # ns1 TCP   -> ns1 (10.0.1.1:10002      ) MPTCP	(duration    30ms) [ OK ]
  | # ns1 MPTCP -> ns1 (dead:beef:1::1:10003) MPTCP	(duration   120ms) [ OK ]
  | # ns1 MPTCP -> ns1 (dead:beef:1::1:10004) TCP  	(duration    40ms) [ OK ]
  | # ns1 TCP   -> ns1 (dead:beef:1::1:10005) MPTCP	(duration    38ms) [ OK ]
  | # ns1 MPTCP -> ns2 (10.0.1.2:10006      ) MPTCP	(duration    40ms) [ OK ]
  | # ns1 MPTCP -> ns2 (dead:beef:1::2:10007) MPTCP	(duration    40ms) [ OK ]
  | # ns1 MPTCP -> ns2 (10.0.2.1:10008      ) MPTCP	(duration    40ms) [ OK ]
  | # ns1 MPTCP -> ns2 (dead:beef:2::1:10009) MPTCP	(duration    40ms) [ OK ]
  | # ns1 MPTCP -> ns3 (10.0.2.2:10010      ) MPTCP	(duration   398ms) [ OK ]
  | # ns1 MPTCP -> ns3 (dead:beef:2::2:10011) MPTCP	(duration  4025ms) [ OK ]
  | # ns1 MPTCP -> ns3 (10.0.3.2:10012       ) MPTCP	copyfd_io_poll: poll timed out (events: POLLIN 1, POLLOUT 0)
  | # (duration 30375ms) [ FAIL ] client exit code 0, server 2
  | #
  | # netns ns3-60559cc5-rBzcRI socket stat for 10012:
  | # Netid State      Recv-Q Send-Q Local  Address:Port  Peer Address:Port Process
  | # tcp   ESTAB      0      0           10.0.3.2:10012     10.0.1.1:60486 ino:0 sk:1 <->
  | # ts sack cubic wscale:7,7 rto:229  rtt:28.164/0.01 ato:40 mss:1448 pmtu:1500 rcvmss:1448 advmss:1448  cwnd:120 bytes_sent:172060 bytes_acked:172060 bytes_received:3849244  segs_out:273 segs_in:2804 data_segs_out:129 data_segs_in:2717 send  49356625bps lastsnd:30356 lastrcv:30215 lastack:30215 pacing_rate  98711496bps delivery_rate 411272bps delivered:130 busy:141ms  rcv_rtt:28.223 rcv_space:14600 rcv_ssthresh:3133018 minrtt:28.092  tcp-ulp-mptcp flags:Mec token:0000(id:0)/ecb40f0(id:0)  seq:38a74c261fe11c26 sfseq:39f805 ssnoff:b001648f maplen:c418
  | # mptcp FIN-WAIT-2 0      0            10.0.3.2:10012     10.0.1.1:60486 timer:(keepalive,59sec,0) ino:0 sk:2  ---
  | # remote_key token:ecb40f0  write_seq:7f38dd7279190bfe snd_una:7f38dd7279190bfe  rcv_nxt:38a74c261fe1e03e
  | # TcpPassiveOpens                 1                  0.0
  | # TcpInSegs                       242                0.0
  | # TcpOutSegs                      274                0.0
  | # TcpExtTCPPureAcks               83                 0.0
  | # TcpExtTCPBacklogCoalesce        2                  0.0
  | # TcpExtTCPOFOQueue               1                  0.0
  | # TcpExtTCPAutoCorking            1                  0.0
  | # TcpExtTCPOrigDataSent           129                0.0
  | # TcpExtTCPDelivered              129                0.0
  | # MPTcpExtMPCapableSYNRX          1                  0.0
  | # MPTcpExtMPCapableACKRX          1                  0.0
  | #
  | # netns ns1-60559cc5-rBzcRI socket stat for 10012:
  | # Netid State    Recv-Q Send-Q Local  Address:Port  Peer Address:Port Process
  | # tcp   ESTAB    0      0           10.0.1.1:60486     10.0.3.2:10012 ino:0 sk:3 <->
  | # ts sack cubic wscale:7,7 rto:229  rtt:28.142/0.017 ato:48 mss:1448 pmtu:1500 rcvmss:1420 advmss:1448  cwnd:1648 bytes_sent:3849244 bytes_acked:3849245 bytes_received:172060  segs_out:2805 segs_in:274 data_segs_out:2717 data_segs_in:129 send  678360884bps lastsnd:30304 lastrcv:30417 lastack:30276 pacing_rate  1356709712bps delivery_rate 335399688bps delivered:2718 busy:282ms  rwnd_limited:28ms(9.9%) reordering:7 reord_seen:1 rcv_rtt:28.348  rcv_space:14480 rcv_ssthresh:265072 minrtt:28.13 tcp-ulp-mptcp  flags:Mmec token:0000(id:0)/ddcec3e3(id:0) seq:7f38dd7279190be1  sfseq:2a001 ssnoff:64d68060 maplen:1c
  | # mptcp LAST-ACK 0      0            10.0.1.1:60486     10.0.3.2:10012 timer:(keepalive,29sec,0) ino:0 sk:4  ---
  | # remote_key token:ddcec3e3  write_seq:38a74c261fe1e03f snd_una:38a74c261fe1e03e  rcv_nxt:7f38dd7279190bfe
  | # TcpActiveOpens                  1                  0.0
  | # TcpInSegs                       274                0.0
  | # TcpOutSegs                      2805               0.0
  | # TcpExtTCPPureAcks               128                0.0
  | # TcpExtTCPSACKReorder            1                  0.0
  | # TcpExtTCPBacklogCoalesce        25                 0.0
  | # TcpExtTCPSackMerged             1                  0.0
  | # TcpExtTCPSackShiftFallback      1                  0.0
  | # TcpExtTCPAutoCorking            5                  0.0
  | # TcpExtTCPOrigDataSent           2717               0.0
  | # TcpExtTCPACKSkippedSeq          4                  0.0
  | # TcpExtTCPDelivered              2718               0.0
  | # MPTcpExtMPCapableSYNTX          1                  0.0
  | # MPTcpExtMPCapableSYNACKRX       1                  0.0
  | #
  | # ns1 MPTCP -> ns3 (dead:beef:3::2:10013) MPTCP	(duration   342ms) [ OK ]
  | # ns1 MPTCP -> ns4 (10.0.3.1:10014      ) MPTCP	(duration  3375ms) [ OK ]
  | # ns1 MPTCP -> ns4 (dead:beef:3::1:10015) MPTCP	(duration  3971ms) [ OK ]
  | # ns2 MPTCP -> ns1 (10.0.1.1:10016      ) MPTCP	(duration    40ms) [ OK ]
  | # FAIL: Could not even run loopback test