mptcp: pm: ADD_ADDR 0 is not a new address

The ADD_ADDR 0 with the address from the initial subflow should not be
considered as a new address: this is not something new. If the host
receives it, it simply means that the address is available again.

When receiving an ADD_ADDR for the ID 0, the PM already doesn't consider
it as new by not incrementing the 'add_addr_accepted' counter. But the
'accept_addr' might not be set if the limit has already been reached:
this can be bypassed in this case. But before, it is important to check
that this ADD_ADDR for the ID 0 is for the same address as the initial
subflow. If not, it is not something that should happen, and the
ADD_ADDR can be ignored.

Note that if an ADD_ADDR is received while there is already a subflow
opened using the same address, this ADD_ADDR is ignored as well. It
means that if multiple ADD_ADDR for ID 0 are received, there will not be
any duplicated subflows created by the client.

Fixes: d0876b2284cf ("mptcp: add the incoming RM_ADDR support")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 26eb898a202b..3b22313d1b86 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -993,6 +993,8 @@ void mptcp_pm_add_addr_received(const struct sock *ssk,
 void mptcp_pm_add_addr_echoed(struct mptcp_sock *msk,
 			      const struct mptcp_addr_info *addr);
 void mptcp_pm_add_addr_send_ack(struct mptcp_sock *msk);
+bool mptcp_pm_nl_is_init_remote_addr(struct mptcp_sock *msk,
+				     const struct mptcp_addr_info *remote);
 void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk);
 void mptcp_pm_rm_addr_received(struct mptcp_sock *msk,
 			       const struct mptcp_rm_list *rm_list);