On 10/28/25 12:30 PM, Paolo Abeni wrote:
On 10/23/25 2:54 PM, Jiayuan Chen wrote:
When the server has MPTCP enabled but receives a non-MP-capable request from a client, it calls mptcp_fallback_tcp_ops().
Since non-MPTCP connections are allowed to use sockmap, which replaces sk->sk_prot, using sk->sk_prot to determine the IP version in mptcp_fallback_tcp_ops() becomes unreliable. This can lead to assigning incorrect ops to sk->sk_socket->ops.
I don't see how sockmap could modify the to-be-accepted socket sk_prot before mptcp_fallback_tcp_ops(), as such call happens before the fd is installed, and AFAICS sockmap can only fetch sockets via fds.
Is this patch needed?
Matttbe explained off-list the details of how that could happen. I think the commit message here must be more verbose to explain clearly the whys, even to those non proficient in sockmap like me.
Thanks,
Paolo