October 28, 2025 at 20:03, "Paolo Abeni" <[email protected] mailto:[email protected]?to=%22Paolo%20Abeni%22%20%3Cpabeni%40redhat.com%3E > wrote:
> > On 10/23/25 2:54 PM, Jiayuan Chen wrote: > > > > > MPTCP creates subflows for data transmission, and these sockets should not > > be added to sockmap because MPTCP sets specialized data_ready handlers > > that would be overridden by sockmap. > > > > Additionally, for the parent socket of MPTCP subflows (plain TCP socket), > > MPTCP sk requires specific protocol handling that conflicts with sockmap's > > operation(mptcp_prot). > > > > This patch adds proper checks to reject MPTCP subflows and their parent > > sockets from being added to sockmap, while preserving compatibility with > > reuseport functionality for listening MPTCP sockets. > > > It's unclear to me why that is safe. sockmap is going to change the > listener msk proto ops. > > The listener could disconnect and create an egress connection, still > using the wrong ops. sockmap only replaces read/write handler of a sk and keeps another handler. But I agree with you; I also don't think sockmap should replace the handlers of the listen socket. Because for a listen socket, sockmap is merely used as a container, just like hash map or array map. But in reality, that's exactly what it does... > I think sockmap should always be prevented for mptcp socket, or at least > a solid explanation of why such exception is safe should be included in > the commit message. > > Note that the first option allows for solving the issue entirely in the > mptcp code, setting dummy/noop psock_update_sk_prot for mptcp sockets > and mptcp subflows. I will do it.
