This script sets net.ipv4.tcp_rto_max_ms to 1000 and checks
if SYN+ACK RTO is capped at 1s for TFO and non-TFO.
Without the previous patch, the max RTO is applied to TFO
SYN+ACK only, and non-TFO SYN+ACK RTO increases exponentially.
# selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt
# TAP version 13
# 1..2
# tcp_rto_synack_rto_max.pkt:46: error handling packet: timing error:
expected outbound packet at 5.091936 sec but happened at 6.107826 sec; tolerance 0.127974 sec
# script packet: 5.091936 S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
# actual packet: 6.107826 S. 0:0(0) ack 1 win 65535 <mss 1460,nop,nop,sackOK>
# not ok 1 ipv4
# tcp_rto_synack_rto_max.pkt:46: error handling packet: timing error:
expected outbound packet at 5.075901 sec but happened at 6.091841 sec; tolerance 0.127976 sec
# script packet: 5.075901 S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
# actual packet: 6.091841 S. 0:0(0) ack 1 win 65535 <mss 1460,nop,nop,sackOK>
# not ok 2 ipv6
# # Totals: pass:0 fail:2 xfail:0 xpass:0 skip:0 error:0
not ok 49 selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt # exit=1
With the previous patch, all SYN+ACKs are retransmitted
after 1s.
# selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt
# TAP version 13
# 1..2
# ok 1 ipv4
# ok 2 ipv6
# # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0
ok 49 selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251106003357.273403-7-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
ffc56c9081