linux-kernelorg-stable/include
Eric Dumazet 3ba075278c tcp: be less liberal in TSEcr received while in SYN_RECV state
Yong-Hao Zou mentioned that linux was not strict as other OS in 3WHS,
for flows using TCP TS option (RFC 7323)

As hinted by an old comment in tcp_check_req(),
we can check the TSEcr value in the incoming packet corresponds
to one of the SYNACK TSval values we have sent.

In this patch, I record the oldest and most recent values
that SYNACK packets have used.

Send a challenge ACK if we receive a TSEcr outside
of this range, and increase a new SNMP counter.

nstat -az | grep TSEcrRejected
TcpExtTSEcrRejected            0                  0.0

Due to TCP fastopen implementation, do not apply yet these checks
for fastopen flows.

v2: No longer use req->num_timeout, but treq->snt_tsval_first
    to detect when first SYNACK is prepared. This means
    we make sure to not send an initial zero TSval.
    Make sure MPTCP and TCP selftests are passing.
    Change MIB name to TcpExtTSEcrRejected

v1: https://lore.kernel.org/netdev/CADVnQykD8i4ArpSZaPKaoNxLJ2if2ts9m4As+=Jvdkrgx1qMHw@mail.gmail.com/T/

Reported-by: Yong-Hao Zou <yonghaoz1994@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250225171048.3105061-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-02-26 18:11:17 -08:00
..
acpi
asm-generic
clocksource
crypto
cxl
drm
dt-bindings
hyperv
keys
kunit
kvm
linux tcp: be less liberal in TSEcr received while in SYN_RECV state 2025-02-26 18:11:17 -08:00
math-emu
media
memory
misc
net mptcp: sched: split get_subflow interface into two 2025-02-24 18:23:44 -08:00
pcmcia
ras
rdma
rv
scsi
soc
sound
target
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-02-20 10:37:30 -08:00
uapi tcp: be less liberal in TSEcr received while in SYN_RECV state 2025-02-26 18:11:17 -08:00
ufs
vdso
video
xen