1. 03 Feb, 2021 1 commit
    • Davide Caratti's avatar
      mptcp: fix length of MP_PRIO suboption · ec99a470
      Davide Caratti authored
      With version 0 of the protocol it was legal to encode the 'Subflow Id' in
      the MP_PRIO suboption, to specify which subflow would change its 'Backup'
      flag. This has been removed from v1 specification: thus, according to RFC
      8684 §3.3.8, the resulting 'Length' for MP_PRIO changed from 4 to 3 byte.
      
      Current Linux generates / parses MP_PRIO according to the old spec, using
      'Length' equal to 4, and hardcoding 1 as 'Subflow Id'; RFC compliance can
      improve if we change 'Length' in other to become 3, leaving a 'Nop' after
      the MP_PRIO suboption. In this way the kernel will emit and accept *only*
      MP_PRIO suboptions that are compliant to version 1 of the MPTCP protocol.
      
       unpatched 5.11-rc kernel:
       [root@bottarga ~]# tcpdump -tnnr unpatched.pcap | grep prio
       reading from file unpatched.pcap, link-type LINUX_SLL (Linux cooked v1)
       dropped privs to tcpdump
       IP 10.0.3.2.48433 > 10.0.1.1.10006: Flags [.], ack 1, win 502, options [nop,nop,TS val 4032325513 ecr 1876514270,mptcp prio non-backup id 1,mptcp dss ack 14084896651682217737], length 0
      
       patched 5.11-rc kernel:
       [root@bottarga ~]# tcpdump -tnnr patched.pcap | grep prio
       reading from file patched.pcap, link-type LINUX_SLL (Linux cooked v1)
       dropped privs to tcpdump
       IP 10.0.3.2.49735 > 10.0.1.1.10006: Flags [.], ack 1, win 502, options [nop,nop,TS val 1276737699 ecr 2686399734,mptcp prio non-backup,nop,mptcp dss ack 18433038869082491686], length 0
      
      Changes since v2:
       - when accounting for option space, don't increment 'TCPOLEN_MPTCP_PRIO'
         and use 'TCPOLEN_MPTCP_PRIO_ALIGN' instead, thanks to Matthieu Baerts.
      Changes since v1:
       - refactor patch to avoid using 'TCPOLEN_MPTCP_PRIO' with its old value,
         thanks to Geliang Tang.
      
      Fixes: 06706542 ("mptcp: add the outgoing MP_PRIO support")
      Reviewed-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
      Reviewed-by: default avatarMatthieu Baerts <matthieu.baerts@tessares.net>
      Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
      Reviewed-by: default avatarMatteo Croce <mcroce@linux.microsoft.com>
      Link: https://lore.kernel.org/r/846cdd41e6ad6ec88ef23fee1552ab39c2f5a3d1.1612184361.git.dcaratti@redhat.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      ec99a470
  2. 02 Feb, 2021 39 commits