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alistair23-linux/net
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Yuchung Cheng fcc2202a9d tcp: fix undo spurious SYNACK in passive Fast Open 
Commit 794200d662 ("tcp: undo cwnd on Fast Open spurious SYNACK
retransmit") may cause tcp_fastretrans_alert() to warn about pending
retransmission in Open state. This is triggered when the Fast Open
server both sends data and has spurious SYNACK retransmission during
the handshake, and the data packets were lost or reordered.

The root cause is a bit complicated:

(1) Upon receiving SYN-data: a full socket is created with
    snd_una = ISN + 1 by tcp_create_openreq_child()

(2) On SYNACK timeout the server/sender enters CA_Loss state.

(3) Upon receiving the final ACK to complete the handshake, sender
    does not mark FLAG_SND_UNA_ADVANCED since (1)

    Sender then calls tcp_process_loss since state is CA_loss by (2)

(4) tcp_process_loss() does not invoke undo operations but instead
    mark REXMIT_LOST to force retransmission

(5) tcp_rcv_synrecv_state_fastopen() calls tcp_try_undo_loss(). It
    changes state to CA_Open but has positive tp->retrans_out

(6) Next ACK triggers the WARN_ON in tcp_fastretrans_alert()

The step that goes wrong is (4) where the undo operation should
have been invoked because the ACK successfully acknowledged the
SYN sequence. This fixes that by specifically checking undo
when the SYN-ACK sequence is acknowledged. Then after
tcp_process_loss() the state would be further adjusted based
in tcp_fastretrans_alert() to avoid triggering the warning in (6).

Fixes: 794200d662 ("tcp: undo cwnd on Fast Open spurious SYNACK retransmit")
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-06-09 20:04:11 -07:00
..
6lowpan treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
9p treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 188 2019-05-30 11:29:21 -07:00
802 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
8021q treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
appletalk treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
atm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
ax25 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
batman-adv This feature/cleanup patchset includes the following patches: 2019-05-09 09:44:17 -07:00
bluetooth treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
bpf treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
bpfilter treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
bridge treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
caif treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 194 2019-05-30 11:29:22 -07:00
can can: purge socket error queue on sock destruct 2019-06-07 23:03:54 +02:00
ceph treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
core Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2019-06-07 14:46:47 -07:00
dcb treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
dccp treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
decnet treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 53 2019-05-24 17:36:42 +02:00
dns_resolver treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
dsa Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-06-07 09:29:14 -07:00
ethernet treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
hsr hsr: fix don't prune the master node from the node_db 2019-05-23 09:29:44 -07:00
ieee802154 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
ife treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ipv4 tcp: fix undo spurious SYNACK in passive Fast Open 2019-06-09 20:04:11 -07:00
ipv6 ipv6: flowlabel: fl6_sock_lookup() must use atomic_inc_not_zero 2019-06-09 13:07:14 -07:00
iucv treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 153 2019-05-30 11:26:32 -07:00
kcm treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
key treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
l2tp treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
l3mdev treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
lapb treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 41 2019-05-24 17:27:12 +02:00
llc llc: fix skb leak in llc_build_and_send_ui_pkt() 2019-05-28 17:25:23 -07:00
mac80211 treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
mac802154 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
mpls mpls: fix af_mpls dependencies 2019-06-09 19:57:24 -07:00
ncsi treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
netfilter SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
netlabel treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
netlink treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
netrom treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
nfc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
nsh treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
openvswitch treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
packet Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-06-07 09:29:14 -07:00
phonet SPDX update for 5.2-rc2, round 1 2019-05-21 12:33:38 -07:00
psample treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
qrtr Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-05-22 08:28:16 -07:00
rds net: rds: fix memory leak in rds_ib_flush_mr_pool 2019-06-06 10:32:16 -07:00
rfkill treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
rose treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
rxrpc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sched SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
sctp Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-06-07 09:29:14 -07:00
smc treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
strparser treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
sunrpc SUNRPC: Fix a use after free when a server rejects the RPCSEC_GSS credential 2019-05-30 15:29:41 -04:00
switchdev treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
tipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-05-22 08:28:16 -07:00
tls net/tls: replace the sleeping lock around RX resync with a bit lock 2019-06-04 13:34:37 -07:00
unix treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
vmw_vsock treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
wimax treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
wireless treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
x25 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 41 2019-05-24 17:27:12 +02:00
xdp treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
xfrm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
compat.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile
socket.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
sysctl_net.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00