commit 2293c57484 upstream.
During the connection establishment, a peer can tell the other one that
it cannot establish new subflows to the initial IP address and port by
setting the 'C' flag [1]. Doing so makes sense when the sender is behind
a strict NAT, operating behind a legacy Layer 4 load balancer, or using
anycast IP address for example.
When this 'C' flag is set, the path-managers must then not try to
establish new subflows to the other peer's initial IP address and port.
The in-kernel PM has access to this info, but the userspace PM didn't.
The RFC8684 [1] is strict about that:
(...) therefore the receiver MUST NOT try to open any additional
subflows toward this address and port.
So it is important to tell the userspace about that as it is responsible
for the respect of this flag.
When a new connection is created and established, the Netlink events
now contain the existing but not currently used 'flags' attribute. When
MPTCP_PM_EV_FLAG_DENY_JOIN_ID0 is set, it means no other subflows
to the initial IP address and port -- info that are also part of the
event -- can be established.
Link: https://datatracker.ietf.org/doc/html/rfc8684#section-3.1-20.6 [1]
Fixes: 702c2f646d ("mptcp: netlink: allow userspace-driven subflow establishment")
Reported-by: Marek Majkowski <marek@cloudflare.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/532
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250912-net-mptcp-pm-uspace-deny_join_id0-v1-2-40171884ade8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in mptcp_pm.yaml, because the indentation has been modified
in commit ec362192aa ("netlink: specs: fix up indentation errors"),
which is not in this version. Applying the same modifications, but at
a different level. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We assume in handful of places that the name of the spec is
the same as the name of the family. We could fix that but
it seems like a fair assumption to make. Rename the MPTCP
spec instead.
Reviewed-by: Mat Martineau <martineau@kernel.org>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
allow specifying cmd-cnt-name and cmd-max-name in netlink specs, in
accordance with Documentation/userspace-api/netlink/c-code-gen.rst.
Use cmd-cnt-name and attr-cnt-name in the mptcp yaml spec and in the
corresponding uAPI headers, to preserve the #defines we had in the past
and avoid adding new ones.
v2:
- squash modification in mptcp.yaml and MPTCP uAPI headers
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/12d4ed0116d8883cf4b533b856f3125a34e56749.1698415310.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Matthieu Baerts (NGI0)
Jakub Kicinski
Davide Caratti