Add a packetdrill reproducer for the free_space-limited scaled no-shrink quantization case.
Grow rcv_ssthresh with in-order data, then queue tiny OOO skbs so receive memory drives raw free_space just below rcv_ssthresh without advancing rcv_nxt. The final ACK reaches the case where raw free_space sits just above 84 scaled units while rcv_ssthresh stays slightly larger. Old code rounds that final free_space value up and advertises 85. With the fix, the ACK stays at 84. This gives fail-before/pass-after coverage for the actual raw free_space bug rather than the separate rcv_ssthresh-limited ALIGN-up behavior. Signed-off-by: Wesley Atwell <[email protected]> --- v2: - replace the old rcv_ssthresh-limited sequence with an OOO-memory reproducer for the raw free_space case - drop the follow-on ACK transition and keep the final free_space failure case that proves the bug - drop the IPv4-only restriction after verifying the test passes for ipv4, ipv6, and ipv4-mapped-ipv6 - reword the in-file comments to describe the observed behavior without referring to a removed path as "buggy" .../packetdrill/tcp_rcv_quantization_credit.pkt | 62 ++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt new file mode 100644 index 000000000000..bb4f63772326 --- /dev/null +++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 + +--mss=1000 + +`./defaults.sh +sysctl -q net.ipv4.tcp_moderate_rcvbuf=0 +sysctl -q net.ipv4.tcp_shrink_window=0 +sysctl -q net.ipv4.tcp_rmem="4096 131072 $((32*1024*1024))"` + +// Exercise the scaled no-shrink path when raw backed free_space, not +// rcv_ssthresh, limits the post-ACK window in __tcp_select_window(). +// +// Grow rcv_ssthresh with in-order data, then queue tiny OOO skbs so receive +// memory drops raw free_space to just over 84 scaled units while the current +// rcv_ssthresh stays slightly larger. The final OOO ACK should keep the +// sender-visible window at 84 rather than reopening it to 85. + +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + + +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7> + +0 > S. 0:0(0) ack 1 <mss 1460,nop,wscale 10> + +0 < . 1:1(0) ack 1 win 257 + + +0 accept(3, ..., ...) = 4 + + +0 < P. 1:10001(10000) ack 1 win 257 + * > . 1:1(0) ack 10001 + + +0 < P. 10001:11024(1023) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 12024:12025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 13024:13025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 14024:14025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 15024:15025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 16024:16025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 17024:17025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 18024:18025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 19024:19025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + +// The last tiny OOO skb pushes raw free_space just below rcv_ssthresh +// without crossing the next lower scaled unit. + +0 < P. 20024:20025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 win 84 + +0 %{ assert (tcpi_rcv_wnd >> 10) == 84, tcpi_rcv_wnd }% -- 2.43.0
