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[ Upstream commit8e56b063c8] In Scenario A and B below, as the delayed INIT_ACK always changes the peer vtag, SCTP ct with the incorrect vtag may cause packet loss. Scenario A: INIT_ACK is delayed until the peer receives its own INIT_ACK 192.168.1.2 > 192.168.1.1: [INIT] [init tag: 1328086772] 192.168.1.1 > 192.168.1.2: [INIT] [init tag: 1414468151] 192.168.1.2 > 192.168.1.1: [INIT ACK] [init tag: 1328086772] 192.168.1.1 > 192.168.1.2: [INIT ACK] [init tag: 1650211246] * 192.168.1.2 > 192.168.1.1: [COOKIE ECHO] 192.168.1.1 > 192.168.1.2: [COOKIE ECHO] 192.168.1.2 > 192.168.1.1: [COOKIE ACK] Scenario B: INIT_ACK is delayed until the peer completes its own handshake 192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 3922216408] 192.168.1.1 > 192.168.1.2: sctp (1) [INIT] [init tag: 144230885] 192.168.1.2 > 192.168.1.1: sctp (1) [INIT ACK] [init tag: 3922216408] 192.168.1.1 > 192.168.1.2: sctp (1) [COOKIE ECHO] 192.168.1.2 > 192.168.1.1: sctp (1) [COOKIE ACK] 192.168.1.1 > 192.168.1.2: sctp (1) [INIT ACK] [init tag: 3914796021] * This patch fixes it as below: In SCTP_CID_INIT processing: - clear ct->proto.sctp.init[!dir] if ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir]. (Scenario E) - set ct->proto.sctp.init[dir]. In SCTP_CID_INIT_ACK processing: - drop it if !ct->proto.sctp.init[!dir] && ct->proto.sctp.vtag[!dir] && ct->proto.sctp.vtag[!dir] != ih->init_tag. (Scenario B, Scenario C) - drop it if ct->proto.sctp.init[dir] && ct->proto.sctp.init[!dir] && ct->proto.sctp.vtag[!dir] != ih->init_tag. (Scenario A) In SCTP_CID_COOKIE_ACK processing: - clear ct->proto.sctp.init[dir] and ct->proto.sctp.init[!dir]. (Scenario D) Also, it's important to allow the ct state to move forward with cookie_echo and cookie_ack from the opposite dir for the collision scenarios. There are also other Scenarios where it should allow the packet through, addressed by the processing above: Scenario C: new CT is created by INIT_ACK. Scenario D: start INIT on the existing ESTABLISHED ct. Scenario E: start INIT after the old collision on the existing ESTABLISHED ct. 192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 3922216408] 192.168.1.1 > 192.168.1.2: sctp (1) [INIT] [init tag: 144230885] (both side are stopped, then start new connection again in hours) 192.168.1.2 > 192.168.1.1: sctp (1) [INIT] [init tag: 242308742] Fixes:9fb9cbb108("[NETFILTER]: Add nf_conntrack subsystem.") Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.