diff options
| author | Davide Caratti <dcaratti@redhat.com> | 2021-02-01 16:05:26 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-02-03 04:34:02 +0300 |
| commit | ec99a470c7d5517c97dee6dd7953275a92c63834 (patch) | |
| tree | 146e906b492d5a850f859a5ed721aa4c8b694abf /net/mptcp/options.c | |
| parent | c96b0a39705177eeef60246d084874936bf0b0e0 (diff) | |
| download | linux-ec99a470c7d5517c97dee6dd7953275a92c63834.tar.xz | |
mptcp: fix length of MP_PRIO suboption
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 ยง3.3.8, 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: 067065422fcd ("mptcp: add the outgoing MP_PRIO support")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Matteo Croce <mcroce@linux.microsoft.com>
Link: https://lore.kernel.org/r/846cdd41e6ad6ec88ef23fee1552ab39c2f5a3d1.1612184361.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/mptcp/options.c')
| -rw-r--r-- | net/mptcp/options.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/net/mptcp/options.c b/net/mptcp/options.c index c9643344a8d7..17ad42c65087 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -699,10 +699,11 @@ static bool mptcp_established_options_mp_prio(struct sock *sk, if (!subflow->send_mp_prio) return false; - if (remaining < TCPOLEN_MPTCP_PRIO) + /* account for the trailing 'nop' option */ + if (remaining < TCPOLEN_MPTCP_PRIO_ALIGN) return false; - *size = TCPOLEN_MPTCP_PRIO; + *size = TCPOLEN_MPTCP_PRIO_ALIGN; opts->suboptions |= OPTION_MPTCP_PRIO; opts->backup = subflow->request_bkup; |