Re: [PATCH mptcp-next v5 06/16] mptcp: implement psock_update_sk_prot for sockmap

[Geliang Tang <geliang@kernel.org>]

Hi Matt,

On Sun, 2026-09-13 at 20:22 +0200, Matthieu Baerts wrote:
> On 13/09/2026 12:14, Geliang Tang wrote:
> > From: Geliang Tang <tanggeliang@kylinos.cn>
> > 
> > This patch adds basic MPTCP support for BPF sockmap by implementing
> > the
> > psock_update_sk_prot callback (mptcp_bpf_update_proto). This allows
> > MPTCP
> > sockets to be added to sockmap and enables the sk_skb
> > stream_verdict
> > redirect path via the read_skb callback. Separate protocol
> > structures are
> > maintained for IPv4/IPv6 and BASE/TX/RX/TXRX configurations,
> > mirroring
> > tcp_bpf_update_proto(). The IPv6 variant is lazily rebuilt via
> > mptcp_bpf_check_v6_needs_rebuild() when the underlying protocol ops
> > change.
> > 
> > MPTCP delegates to the original protocol operations so that MPTCP-
> > specific
> > logic (multi-path scheduling in sendmsg, ordered reassembly in
> > recvmsg) is
> > preserved. recvmsg is overridden in all BPF configurations with
> > mptcp_bpf_recvmsg, which checks the psock ingress queue first and
> > falls
> > back to mptcp_recvmsg via the shared __tcp_bpf_recvmsg() helper.
> > sendmsg
> > is overridden in the TX/TXRX configurations with mptcp_bpf_sendmsg,
> > which
> > processes sk_msg redirect before delegating to mptcp_sendmsg via
> > __tcp_bpf_sendmsg().
> > 
> > Export mptcp_sendmsg, mptcp_recvmsg and mptcp_prot from protocol.c
> > so they
> > can be referenced by bpf.c.
> > 
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes:
> > https://lore.kernel.org/oe-kbuild-all/202512261144.DxrvwMS3-lkp@intel.com/
> > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/521
> > Cc: Cong Wang <xiyou.wangcong@gmail.com>
> > Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> > ---
> >  include/net/tcp.h    |   5 ++
> >  net/ipv4/tcp_bpf.c   |  29 +++++++---
> 
> Probably best to separate this change from the rest: TCP/BPF on one
> side, then MPTCP/BPF (and eventually MPTCP only before, just to do
> the
> exports.)

I agree, and will update it in the next version.

Thanks,
-Geliang

> 
> >  net/mptcp/bpf.c      | 129
> > +++++++++++++++++++++++++++++++++++++++++++
> >  net/mptcp/protocol.c |  10 ++--
> >  net/mptcp/protocol.h |  18 ++++++
> 
> Cheers,
> Matt