Re: [PATCH v7 0/2] bpf, sockmap: handle spurious tcp_msg_wait_data() wakeup

[Nnamdi Onyeyiri]

On Tue, Jul 21, 2026 at 11:38:05PM +0100, Nnamdi Onyeyiri wrote:
> Spurious wakeups in tcp_msg_wait_data() aren't being handled by
> tcp_bpf_recvmsg() and tcp_bpf_recvmsg_parser(), leading to unexpected
> EAGAIN errors returned by recvfrom()/recv().  Adding handling for the
> wakeup and a selftest.
> 
> This issue was first discovered in an application that adds sockets to
> a sockmap as a way to view the received data.  No redirects or any
> other operations are performed.
> 
> Sashiko has noted a few other pre-existing issues in the same area
> (https://patch.msgid.link/20260714205118.17DB11F000E9@xxxxxxxxxxxxxxx)
> that can lead to EAGAIN in tcp_bpf_recvmsg() and
> tcp_bpf_recvmsg_parser().  A local run of Sashiko also identified a
> potential issue in tcp_bpf_recvmsg() handling zero-data FIN packets when
> the MSG_PEEK flag is set.  To prevent this patchset from growing too
> large, I intend to submit follow up patches to address these once this
> one has been accepted.
> 
> Changes in v7:
> - In tcp_bpf_recvmsg check for data in the TCP_CLOSE, !timeo and
>   signal_pending branches.
> - Refactored changes to tcp_bpf_recvmsg to reduce duplication.
> - Increase the number of iterations in the selftests.
> - Documented selftests numeric constants.
> - Link to v6: https://patch.msgid.link/20260720171535.67867-1-nnamdio@xxxxxxxxx
> 
> Changes in v6:
> - Closing the file descriptor in the selftest worker thread.
> - Ensuring the selftest loop breaks early for an error in the worker
>   thread.
> - Added comments to selftest regarding focus on EAGAIN error.
> - Updated selftest commit message to imperative mood.
> - Link to v5: https://patch.msgid.link/20260717155348.54975-1-nnamdio@xxxxxxxxx
> 
> Changes in v5:
> - Move selftest from net into bpf/prog_tests/sockmap_basic.c
> - Link to v4: https://patch.msgid.link/20260715213538.37229-1-nnamdio@xxxxxxxxx
> 
> Changes in v4:
> - Fix potential data loss in tcp_bpf_recvmsg() when a FIN or RST has
>   been received.
> - Check the return code of pthread_create() in the selftest.
> - Fix race caused by using EXPECT macros in a thread in selftest.
> - Link to v3: https://patch.msgid.link/20260714203927.32289-1-nnamdio@xxxxxxxxx
> 
> Changes in v3:
> - Added the sockmap_recvfrom selftest.
> - Link to v2: https://patch.msgid.link/alFRK66z45eDNZA7@localhost.localdomain
> 
> Changes in v2:
> - In tcp_bpf_recvmsg, handle signals and the socket closing in the loop.
> - Fix spurious wakeups when SO_RCVTIMEO has been set on the socket.
> - Link to v1: https://patch.msgid.link/ak_rR-Skd8Mvn4mH@localhost.localdomain
> 
> Signed-off-by: Nnamdi Onyeyiri <nnamdio@xxxxxxxxx>
> ---
> Nnamdi Onyeyiri (2):
>   bpf, sockmap: handle spurious tcp_msg_wait_data() wakeup
>   selftests/bpf: add sockmap recvfrom EAGAIN selftest
> 
>  net/ipv4/tcp_bpf.c                            |  72 ++++++++--
>  .../selftests/bpf/prog_tests/sockmap_basic.c  | 136 ++++++++++++++++++
>  2 files changed, 199 insertions(+), 9 deletions(-)
> 
> -- 
> 2.52.0
> 

Hi all, just wondering if you need anything more from me on this?