| Message ID | cover.1708082765.git.pabeni@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | mptcp: implement TCP_NOTSENT_LOWAT support | expand |
On Fri, 16 Feb 2024, Paolo Abeni wrote: > Patch 6/7 does the magic, all the others are minor cleanup and fix of > buglet exposed by such feature. I'll push a paired pktdrill test. > > Note that this relies on the existing accounting for snd_nxt. As I > stated such accounting is not 110% accurate as it tracks the most recent > sequence number queued to any subflow, and not the actual sequence > number sent on the wire. > > I experimented a lot trying to implement the latter and in the end it > proved to be both "too complex" and "not necessary". > > The complexity raises from the need for additional lock and a lot of > refactory to introduce such protection without adding significant > overhead. Additionally, snd_nxt is currenly used and exposed with the > current semantic both eBPF and the internal packet scheduling. > Introducing a different tracking will still require us to keep the old > one. > > More interesting, a more accurate tracking could be not strictly > necessary: as the MPTCP protocol enqueues data to the subflows only up > the available send window, any enqueue data is sent on the wire > instantly, without any blocking operation short of a drop in the tx path > at the nft or TC layer. > > The individual patches changelog carry the gory details. > v3 of the series LGTM, thanks Paolo. Matthieu note that this series is split between mptcp-net and mptcp-next: > Still sending a single series to outline the functional requirements, > even if the first 3 patches could land on mptcp-net directly. > Reviewed-by: Mat Martineau <martineau@kernel.org> > v2 -> v3: > - typo in patch 1/7 > - dropped unused code in patch 3/7 > - dropped duplicate code in patch 6/7 > > v1 -> v2: > - clarifiy commit message in patch 1/7 > - fix possible wake-up bug in patch 6/7 > > *** BLURB HERE *** > > Paolo Abeni (7): > mptcp: push at DSS boundaries > mptcp: fix snd_wnd initialization for passive socket > mptcp: fix potential wake-up event loss > mptcp: cleanup writer wake-up > mptcp: avoid some duplicate code in socket option handling > mptcp: implement TCP_NOTSENT_LOWAT support. > mptcp: cleanup SOL_TCP handling > > net/mptcp/protocol.c | 57 ++++++++++++++++++++++++----------- > net/mptcp/protocol.h | 51 ++++++++++++++++++++++--------- > net/mptcp/sockopt.c | 71 ++++++++++++++++++++------------------------ > 3 files changed, 108 insertions(+), 71 deletions(-) > > -- > 2.43.0 > > >
Hi Paolo, Mat, On 16/02/2024 12:28, Paolo Abeni wrote: > Patch 6/7 does the magic, all the others are minor cleanup and fix of > buglet exposed by such feature. I'll push a paired pktdrill test. > > Note that this relies on the existing accounting for snd_nxt. As I > stated such accounting is not 110% accurate as it tracks the most recent > sequence number queued to any subflow, and not the actual sequence > number sent on the wire. > > I experimented a lot trying to implement the latter and in the end it > proved to be both "too complex" and "not necessary". > > The complexity raises from the need for additional lock and a lot of > refactory to introduce such protection without adding significant > overhead. Additionally, snd_nxt is currenly used and exposed with the > current semantic both eBPF and the internal packet scheduling. > Introducing a different tracking will still require us to keep the old > one. > > More interesting, a more accurate tracking could be not strictly > necessary: as the MPTCP protocol enqueues data to the subflows only up > the available send window, any enqueue data is sent on the wire > instantly, without any blocking operation short of a drop in the tx path > at the nft or TC layer. > > The individual patches changelog carry the gory details. > > Still sending a single series to outline the functional requirements, > even if the first 3 patches could land on mptcp-net directly. Thank you for the patches, and the reviews! Now in our tree (fixes for -net, and feat. for net-next): New patches for t/upstream-net and t/upstream: - d9b01cb9adc7: mptcp: push at DSS boundaries - 1ea124e2ca57: mptcp: fix snd_wnd initialization for passive socket - c64351cfe29e: mptcp: fix potential wake-up event loss - Results: 086d253b7038..9dcf86462a59 (export-net) - efe1cf277159: conflict in top-bases/t/DO-NOT-MERGE-git-markup-net-next - Results: 8de48203098c..4f7ce06a0f9e (export) New patches for t/upstream (only): - 232c91fcaf38: mptcp: cleanup writer wake-up - 1e762225d9b2: mptcp: avoid some duplicate code in socket option handling - 51913f3f330f: mptcp: implement TCP_NOTSENT_LOWAT support - eb5db737fdac: mptcp: cleanup SOL_TCP handling - Results: 4f7ce06a0f9e..f2fb9bec2195 (export) Cheers, Matt