On Wed, Mar 11, 2026 at 8:56 AM Wesley Atwell <[email protected]> wrote: > > This series keeps sender-visible TCP receive-window accounting tied to the > scaling basis that was in force when the window was advertised. > > Problem > ------- > > `tp->rcv_wnd` is an advertised promise to the sender, but later > receive-memory admission and clamping could reconstruct that promise > through the mutable live `scaling_ratio`. After ratio drift, the stack > could retain or advertise a receive window that no longer matched the > local hard rmem budget. > > Fix > --- > > - store the advertise-time scaling basis alongside `tp->rcv_wnd` > - refresh that pair at the TCP and MPTCP receive-window write sites > - consume the snapshot in receive-memory admission, clamping, and the > scaled-window quantization path > - preserve the snapshot across `TCP_REPAIR_WINDOW` restore when userspace > provides it, and fall back safely when legacy userspace cannot > - expose the accounting in tracepoints and cover the ABI/runtime contract > in selftests >
Your series will heavily conflict with Simon's one https://patchwork.kernel.org/project/netdevbpf/list/?series=1063486&state=%2A&archive=both I suggest you rebase/retest/resend after we merge it. > Series layout > ------------- > > 1. track the receive-window snapshot state and helpers > 2. refresh the snapshot when TCP advertises or initializes windows > 3. use the snapshot in receive-memory admission and clamping > 4. extend `TCP_REPAIR_WINDOW` for exact restore plus legacy compatibility > 5. refresh the TCP shadow window snapshot in MPTCP > 6. expose rmem/backlog state in `rcvbuf_grow` tracepoints > 7. cover legacy and extended repair-window layouts in selftests > > Testing > ------- > > - `git diff --check origin/main..HEAD` > - `scripts/checkpatch.pl --strict --show-types` on patches 1-7 > - `make -j8 headers` > - `make -j8 net/ipv4/tcp_input.o net/ipv4/tcp_output.o > net/ipv4/tcp_minisocks.o net/ipv4/tcp.o` > - `make -j8 C=1 CF='-D__CHECK_ENDIAN__' W=1 net/ipv4/tcp_input.o > net/ipv4/tcp_output.o net/ipv4/tcp_minisocks.o net/ipv4/tcp.o` > - `make SPHINXDIRS='networking/net_cachelines' htmldocs` > - `make -j8 vmlinux bzImage modules` > - `make -C tools/testing/selftests/net/tcp_ao -j8` > - `make -C tools/testing/selftests/net/mptcp -j8` > - `packetdrill --dry_run` for `tcp_rcv_toobig.pkt` and > `tcp_rcv_toobig_default.pkt` > - `virtme-run` guest pass for both packetdrill tests > - feature-enabled guest pass for `restore_ipv4`, `self-connect_ipv4`, and > `mptcp_sockopt.sh` > > Thanks, > Wesley > > --- > base-commit: 908c344d5cfa0ee6efb3226d22ea661e078ebfa0 > -- > 2.43.0 >
