From: Geliang Tang <tanggeliang@kylinos.cn>

v5:
 - patch 2: new patch - rewrite mptcp_inq_hint() to use mptcp_data_avail()
   instead of ack_seq - map_seq, completely avoiding TFO overflow issues.
 - patch 3: new patch - add TFO SIOCINQ overflow detection in
   mptcp_connect test to catch INT_MAX returns on TFO connections.
 - patch 4: mptcp_inq() now returns INT_MAX instead of 0 when avail >=
   INT_MAX. Removed mptcp_inq_hint() changes (moved to patch 2).
 - patch 6: replace mptcp_rtx_head() check with MPTCP_WORK_RTX and
   MPTCP_RETRANSMIT flag checks in mptcp_rate_check_app_limited() to
   properly detect pending retransmissions without data race issues.

v4:
 - patch 2: fix mptcp_inq_hint() to return 0 instead of INT_MAX on
   passive TFO overflow (ack_seq - map_seq >= INT_MAX).
 - patch 4: add mptcp_rtx_head(sk) to the early-return check in
   mptcp_rate_check_app_limited() so pending retransmissions also
   prevent false app-limited marking.
 - patch 5: update comment message.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1793588257.git.tanggeliang@kylinos.cn/

v3:
 - patch 2: drop DATA_FIN subtraction in mptcp_inq(), remove the
   intermediate 'answ' variable and return (unsigned int)avail
   directly. Update commit message accordingly.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1793324316.git.tanggeliang@kylinos.cn/

v2:
 - drop the patch "prevent dummy DATA_FIN on RST in fallback mode".
 - keep mptcp_inq_hint in mptcp_ioctl unchanged.
 - use mptcp_data_avail in mptcp_inq.
 - add msk_owned_by_me check in mptcp_sendmsg_locked.
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1793258749.git.tanggeliang@kylinos.cn/

v1:
 - https://patchwork.kernel.org/project/mptcp/cover/cover.1792999988.git.tanggeliang@kylinos.cn/

This series was previously posted as part of "Reduce the differences
between TCP and MPTCP for TLS usage" v15. It creates the mptcp_inq()
and mptcp_sendmsg_locked() interfaces that are required for the upcoming
MPTCP kTLS and MPTCP sockmap implementations.

The series has been rebased and no longer depends on Paolo's CB layout
refactoring patches (mptcp: drop the mptcp_ooo_try_coalesce() helper,
mptcp: drop the cant_coalesce CB field, mptcp: remove CB offset field,
mptcp: sync mptcp skb cb layout with tcp one, mptcp: defer read_sock
cleanup to mptcp_worker). Those patches are more complex and will be
sent in a separate series.

Patch overview:

1. mptcp: update mptcp_check_readable
 - Align with TCP's sock_is_readable for better TLS compatibility

2. mptcp: prevent dummy DATA_FIN on RST in fallback mode
 - Fix semantic issue where RST on fallback connections would create
   dummy DATA_FIN, causing unnecessary state transitions
 - Add sk_err check to subflow_is_done() to distinguish abortive
   closes (RST) from clean closes (FIN)

3. mptcp: implement peek_len for proto_ops
 - Add mptcp_inq() to report readable bytes at MPTCP level
 - Wire into .peek_len proto_ops for both IPv4 and IPv6
 - Handle 32-bit torn reads by returning 0 instead of INT_MAX
 - Prepare for TLS strparser integration

4. mptcp: add sendmsg_locked to proto_ops
 - Split mptcp_sendmsg() into locked/unlocked variants
 - Expose .sendmsg_locked in proto_ops for TLS send path

5. mptcp: track app-limited state in mptcp_sendmsg
 - Add mptcp_rate_check_app_limited() to mark subflows as app-limited
 - Bail out when MPTCP has unsent data (write_seq != snd_nxt or
   mptcp_send_head() != NULL) to avoid false app-limited marking
 - Enable accurate delivery rate estimation for BBR

6. selftests: mptcp: sockopt: check app_limited
 - Add regression test for app-limited accounting
 - Verify tcpi_delivery_rate_app_limited == 1 after small transfers

Gang Yan (1):
  mptcp: update mptcp_check_readable

Geliang Tang (6):
  mptcp: use mptcp_data_avail in mptcp_inq_hint
  selftests: mptcp: connect: check TFO SIOCINQ overflow
  mptcp: implement peek_len for proto_ops
  mptcp: add sendmsg_locked to proto_ops
  mptcp: track app-limited state in mptcp_sendmsg
  selftests: mptcp: sockopt: check app_limited

 net/mptcp/protocol.c                          | 92 +++++++++++++++----
 .../selftests/net/mptcp/mptcp_connect.c       | 15 +++
 .../selftests/net/mptcp/mptcp_sockopt.c       |  5 +
 3 files changed, 93 insertions(+), 19 deletions(-)

-- 
2.55.0

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Perf: Unstable: 9 failed test(s): error:mptcp-perf error:sched-baseline(18) error:sched-bbr(14) error:sched-clientlim(12) error:sched-cpu-preempt(2) error:sched-mem-pressure(9) error:sched-rmem(16) error:sched-serverlim(28) error:sched-weak-secondary(12) - Critical: mptcp-perf/01-Test_1/client.log: Global Timeout - Critical: sched-baseline/01-slow_primary/client.log: Global Timeout - Critical: sched-baseline/02-tiny_primary/client.log: Global Timeout - Critical: sched-baseline/03-fast_both/client.log: Global Timeout - Critical: sched-baseline/04-balanced/client.log: Global Timeout - Critical: sched-baseline/05-slow_near_primary/client.log: Global Timeout - Critical: sched-baseline/06-slow_secondary/client.log: Global Timeout - Critical: sched-baseline/07-very_fast/client.log: Global Timeout - Critical: sched-baseline/08-shallow_primary/client.log: Global Timeout - Critical: sched-baseline/09-high_lat_primary/client.log: Global Timeout - Critical: sched-baseline/10-huge_lat_primary/client.log: Global Timeout - Critical: sched-baseline/11-high_lat_secondary/client.log: Global Timeout - Critical: sched-baseline/12-huge_lat_secondary/client.log: Global Timeout - Critical: sched-baseline/13-bloated_primary/client.log: Global Timeout - Critical: sched-baseline/14-bloated_secondary/client.log: Global Timeout - Critical: sched-baseline/15-slow_primary_upload/client.log: Global Timeout - Critical: sched-baseline/16-balanced_upload/client.log: Global Timeout - Critical: sched-baseline/17-slow_primary_parallel_4/client.log: Global Timeout - Critical: sched-baseline/18-balanced_parallel_4/client.log: Global Timeout - Critical: sched-bbr/01-slow_primary_bbr/client.log: Global Timeout - Critical: sched-bbr/02-balanced_bbr/client.log: Global Timeout - Critical: sched-bbr/03-slow_near_primary_bbr/client.log: Global Timeout - Critical: sched-bbr/04-high_lat_primary_bbr/client.log: Global Timeout - Critical: sched-bbr/05-huge_lat_primary_bbr/client.log: Global Timeout - Critical: sched-bbr/06-high_lat_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/07-huge_lat_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/08-slow_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/09-very_fast_bbr/client.log: Global Timeout - Critical: sched-bbr/10-bloated_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/11-bloated_slow_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/12-very_bloated_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/13-bad_secondary_bbr/client.log: Global Timeout - Critical: sched-bbr/14-far_secondary_bbr/client.log: Global Timeout - Critical: sched-clientlim/01-slow_primary_bw_5/client.log: Global Timeout - Critical: sched-clientlim/02-balanced_bw_5/client.log: Global Timeout - Critical: sched-clientlim/03-huge_lat_primary_bw_5/client.log: Global Timeout - Critical: sched-clientlim/04-slow_secondary_bw_5/client.log: Global Timeout - Critical: sched-clientlim/05-slow_primary_bw_10/client.log: Global Timeout - Critical: sched-clientlim/06-balanced_bw_10/client.log: Global Timeout - Critical: sched-clientlim/07-huge_lat_primary_bw_10/client.log: Global Timeout - Critical: sched-clientlim/08-slow_secondary_bw_10/client.log: Global Timeout - Critical: sched-clientlim/09-slow_primary_bw_50/client.log: Global Timeout - Critical: sched-clientlim/10-balanced_bw_50/client.log: Global Timeout - Critical: sched-clientlim/11-huge_lat_primary_bw_50/client.log: Global Timeout - Critical: sched-clientlim/12-slow_secondary_bw_50/client.log: Global Timeout - Critical: sched-cpu-preempt/01-shallow_primary/client.log: Global Timeout - Critical: sched-cpu-preempt/02-shallow_primary_cpu_hog/client.log: Global Timeout - Critical: sched-mem-pressure/01-bloated_slow_secondary_receiver_tcp_mem_parallel_1/client.log: Global Timeout - Critical: sched-mem-pressure/02-bloated_slow_secondary_receiver_tcp_mem_parallel_16/client.log: Global Timeout - Critical: sched-mem-pressure/03-bloated_slow_secondary_receiver_tcp_mem_parallel_99/client.log: Global Timeout - Critical: sched-mem-pressure/04-very_bloated_primary_both_tcp_mem_parallel_1/client.log: Global Timeout - Critical: sched-mem-pressure/05-slow_primary_both_tcp_mem_parallel_1/client.log: Global Timeout - Critical: sched-mem-pressure/06-balanced_both_tcp_mem_parallel_1/client.log: Global Timeout - Critical: sched-mem-pressure/07-very_bloated_primary_both_tcp_mem_parallel_10/client.log: Global Timeout - Critical: sched-mem-pressure/08-slow_primary_both_tcp_mem_parallel_10/client.log: Global Timeout - Critical: sched-mem-pressure/09-balanced_both_tcp_mem_parallel_10/client.log: Global Timeout - Critical: sched-rmem/01-slow_primary_rmem_200/client.log: Global Timeout - Critical: sched-rmem/02-balanced_rmem_200/client.log: Global Timeout - Critical: sched-rmem/03-huge_lat_primary_rmem_200/client.log: Global Timeout - Critical: sched-rmem/04-bloated_primary_rmem_200/client.log: Global Timeout - Critical: sched-rmem/05-slow_primary_rmem_800/client.log: Global Timeout - Critical: sched-rmem/06-balanced_rmem_800/client.log: Global Timeout - Critical: sched-rmem/07-huge_lat_primary_rmem_800/client.log: Global Timeout - Critical: sched-rmem/08-bloated_primary_rmem_800/client.log: Global Timeout - Critical: sched-rmem/09-slow_primary_rmem_2000/client.log: Global Timeout - Critical: sched-rmem/10-balanced_rmem_2000/client.log: Global Timeout - Critical: sched-rmem/11-huge_lat_primary_rmem_2000/client.log: Global Timeout - Critical: sched-rmem/12-bloated_primary_rmem_2000/client.log: Global Timeout - Critical: sched-rmem/13-slow_primary_rmem_6000/client.log: Global Timeout - Critical: sched-rmem/14-balanced_rmem_6000/client.log: Global Timeout - Critical: sched-rmem/15-huge_lat_primary_rmem_6000/client.log: Global Timeout - Critical: sched-rmem/16-bloated_primary_rmem_6000/client.log: Global Timeout - Critical: sched-serverlim/01-slow_primary_bw_5_burst_10/client.log: Global Timeout - Critical: sched-serverlim/02-balanced_bw_5_burst_10/client.log: Global Timeout - Critical: sched-serverlim/03-huge_lat_primary_bw_5_burst_10/client.log: Global Timeout - Critical: sched-serverlim/04-slow_secondary_bw_5_burst_10/client.log: Global Timeout - Critical: sched-serverlim/05-slow_primary_bw_5_burst_250/client.log: Global Timeout - Critical: sched-serverlim/06-balanced_bw_5_burst_250/client.log: Global Timeout - Critical: sched-serverlim/07-huge_lat_primary_bw_5_burst_250/client.log: Global Timeout - Critical: sched-serverlim/08-slow_secondary_bw_5_burst_250/client.log: Global Timeout - Critical: sched-serverlim/09-slow_primary_bw_10_burst_10/client.log: Global Timeout - Critical: sched-serverlim/10-balanced_bw_10_burst_10/client.log: Global Timeout - Critical: sched-serverlim/11-huge_lat_primary_bw_10_burst_10/client.log: Global Timeout - Critical: sched-serverlim/12-slow_secondary_bw_10_burst_10/client.log: Global Timeout - Critical: sched-serverlim/13-slow_primary_bw_10_burst_250/client.log: Global Timeout - Critical: sched-serverlim/14-balanced_bw_10_burst_250/client.log: Global Timeout - Critical: sched-serverlim/15-huge_lat_primary_bw_10_burst_250/client.log: Global Timeout - Critical: sched-serverlim/16-slow_secondary_bw_10_burst_250/client.log: Global Timeout - Critical: sched-serverlim/17-slow_primary_bw_50_burst_10/client.log: Global Timeout - Critical: sched-serverlim/18-balanced_bw_50_burst_10/client.log: Global Timeout - Critical: sched-serverlim/19-huge_lat_primary_bw_50_burst_10/client.log: Global Timeout - Critical: sched-serverlim/20-slow_secondary_bw_50_burst_10/client.log: Global Timeout - Critical: sched-serverlim/21-slow_primary_bw_50_burst_250/client.log: Global Timeout - Critical: sched-serverlim/22-balanced_bw_50_burst_250/client.log: Global Timeout - Critical: sched-serverlim/23-huge_lat_primary_bw_50_burst_250/client.log: Global Timeout - Critical: sched-serverlim/24-slow_secondary_bw_50_burst_250/client.log: Global Timeout - Critical: sched-serverlim/25-slow_primary_bw_10_burst_10_wmem_6000/client.log: Global Timeout - Critical: sched-serverlim/26-balanced_bw_10_burst_10_wmem_6000/client.log: Global Timeout - Critical: sched-serverlim/27-slow_primary_bw_50_burst_10_wmem_6000/client.log: Global Timeout - Critical: sched-serverlim/28-balanced_bw_50_burst_10_wmem_6000/client.log: Global Timeout - Critical: sched-weak-secondary/01-weak_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/02-bad_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/03-far_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/04-bloated_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/05-bloated_slow_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/06-very_bloated_secondary/client.log: Global Timeout - Critical: sched-weak-secondary/07-weak_secondary_backup/client.log: Global Timeout - Critical: sched-weak-secondary/08-bad_secondary_backup/client.log: Global Timeout - Critical: sched-weak-secondary/09-far_secondary_backup/client.log: Global Timeout - Critical: sched-weak-secondary/10-bloated_secondary_backup/client.log: Global Timeout - Critical: sched-weak-secondary/11-bloated_slow_secondary_backup/client.log: Global Timeout - Critical: sched-weak-secondary/12-very_bloated_secondary_backup/client.log: Global Timeout ❌
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/41574850749

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/2b9fa93dc527
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1199752


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)