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A simple pkt-drill script to follow can test this condition.

A simple pkt-drill script to follow can test this condition. // // Copyright (c) 2018 Randall Stewart // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // 1. Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // // THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE // ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF // SUCH DAMAGE. // --ip_version=ipv4 0.00 `kldload -n tcp_bbr tcp_rack` +0.00 `sysctl -w net.inet.tcp.hostcache.purgenow=1` +0.00 `sysctl -w net.inet.tcp.syncookies_only=0` +0.00 `sysctl -w net.inet.tcp.syncookies=1` +0.00 `sysctl -w net.inet.tcp.rfc1323=1` +0.00 `sysctl -w net.inet.tcp.sack.enable=1` +0.00 `sysctl -w net.inet.tcp.ecn.enable=2` // Create a TCP endpoint in the ESTABLISHED state. +0.00 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0.00 fcntl(3, F_GETFL) = 0x02 (flags O_RDWR) +0.00 fcntl(3, F_SETFL, O_RDWR | O_NONBLOCK) = 0 +0.00 setsockopt(3, IPPROTO_TCP, TCP_LOG, [4], 4) = 0 +0.00 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) +0.00 > S 0:0(0) win 65535 <mss 1460,nop,wscale 8,sackOK,TS val 100 ecr 0> +0.10 < S. 0:0(0) ack 1 win 32767 <mss 1440,sackOK,TS val 400 ecr 100> +0.00 > . 1:1(0) ack 1 win 65535 <nop,nop,TS val 200 ecr 400> // Change to rack_latest +0.00 setsockopt(3, IPPROTO_TCP, TCP_NODELAY, [1], 4) = 0 +0.00 setsockopt(3, IPPROTO_TCP, TCP_FUNCTION_BLK, {function_set_name="rack", pcbcnt=0}, 36) = 0 +0.00 send(3, ..., 1000, 0) = 1000 +0.00 > P. 1:1001(1000) ack 1 win 65535 <nop,nop,TS val 250 ecr 400> +.10 < . 1:1(0) ack 1001 win 32000 <nop, nop, TS val 500 ecr 250> +0.00 send(3, ..., 1000, 0) = 1000 +0.00 > P. 1001:2001(1000) ack 1 win 65535 <nop,nop,TS val 300 ecr 500> +.10 < . 1:1(0) ack 2001 win 32000 <nop, nop, TS val 600 ecr 300> // cwnd should be 18,280 +0.10 send(3, ..., 25440, 0) = 25440 * > . 2001:3429(1428) ack 1 win 65535 <nop,nop,TS val 400 ecr 600> * > . 3429:4857(1428) ack 1 win 65535 <nop,nop,TS val 500 ecr 600> * > . 4857:6285(1428) ack 1 win 65535 <nop,nop,TS val 600 ecr 600> * > . 6285:7713(1428) ack 1 win 65535 <nop,nop,TS val 700 ecr 600> * > . 7713:9141(1428) ack 1 win 65535 <nop,nop,TS val 800 ecr 600> * > . 9141:10569(1428) ack 1 win 65535 <nop,nop,TS val 900 ecr 600> * > . 10569:11997(1428) ack 1 win 65535 <nop,nop,TS val 900 ecr 600> * > . 11997:13425(1428) ack 1 win 65535 <nop,nop,TS val 1100 ecr 600> * > . 13425:14853(1428) ack 1 win 65535 <nop,nop,TS val 1200 ecr 600> * > . 14853:16281(1428) ack 1 win 65535 <nop,nop,TS val 1300 ecr 600> * > . 16281:17709(1428) ack 1 win 65535 <nop,nop,TS val 1400 ecr 600> // TLP * > . 17709:19137(1428) ack 1 win 65535 <nop,nop,TS val 1500 ecr 600> // TLP * > . 19137:20565(1428) ack 1 win 65535 <nop,nop,TS val 1600 ecr 600> // T-O (cwnd to 1500) * > . 2001:3429(1428) ack 1 win 65535 <nop,nop,TS val 1900 ecr 600> // Send ICMP +0.00 < [2001:3429(1428)] icmp unreachable frag_needed mtu 1200 // Retransmit * > . 2001:3149(1148) ack 1 win 65535 <nop,nop,TS val 2000 ecr 600> * > . 3149:3429(280) ack 1 win 65535 <nop,nop,TS val 2100 ecr 600> +0.10 < . 1:1(0) ack 3429 win 32000 <nop, nop, TS val 700 ecr 2100> // Retransmits of window * > . 3429:4577(1148) ack 1 win 65535 <nop,nop,TS val 2200 ecr 700> * > . 4577:4857(280) ack 1 win 65535 <nop,nop,TS val 2300 ecr 700> // TLP * > . 20565:21713(1148) ack 1 win 65535 <nop,nop,TS val 2400 ecr 700> +.10 < . 1:1(0) ack 21713 win 32000 <nop, nop, TS val 800 ecr 2400> // Tear it down. +0.00 close(3) = 0 * > . 21713:22861(1148) ack 1 win 65535 <nop,nop,TS val 2500 ecr 800> +.00 < . 1:1(0) ack 22861 win 32000 <nop, nop, TS val 900 ecr 2400> * > . 22861:24009(1148) ack 1 win 65535 <nop,nop,TS val 2600 ecr 800> * > . 24009:25157(1148) ack 1 win 65535 <nop,nop,TS val 2700 ecr 800> +.00 < . 1:1(0) ack 25157 win 32000 <nop, nop, TS val 1000 ecr 2700> * > . 25157:26305(1148) ack 1 win 65535 <nop,nop,TS val 2800 ecr 800> * > P. 26305:27441(1136) ack 1 win 65535 <nop,nop,TS val 2900 ecr 1000> +.00 < . 1:1(0) ack 27441 win 32000 <nop, nop, TS val 1100 ecr 2900> +0.00 > F. 27441:27441(0) ack 1 win 65535 <nop,nop,TS val 3000 ecr 1100> +0.10 < F. 1:1(0) ack 27442 win 32767 <nop,nop,TS val 1200 ecr 3000> +0.00 > . 27442:27442(0) ack 2 win 65535 <nop,nop,TS val 3100 ecr 1200> When running the pkt drill you will have to control-c it without the fix and if you have a tcp log dumper deamon the logging output will show you TLP's going by with no output until you stop the test (or pkt drill times out).

A simple pkt-drill script to follow can test this condition. // // Copyright (c) 2018 Randall Stewart // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // 1. Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // // THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE // ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF // SUCH DAMAGE. // --ip_version=ipv4 0.00 `kldload -n tcp_bbr tcp_rack` +0.00 `sysctl -w net.inet.tcp.hostcache.purgenow=1` +0.00 `sysctl -w net.inet.tcp.syncookies_only=0` +0.00 `sysctl -w net.inet.tcp.syncookies=1` +0.00 `sysctl -w net.inet.tcp.rfc1323=1` +0.00 `sysctl -w net.inet.tcp.sack.enable=1` +0.00 `sysctl -w net.inet.tcp.ecn.enable=2` // Create a TCP endpoint in the ESTABLISHED state. +0.00 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0.00 fcntl(3, F_GETFL) = 0x02 (flags O_RDWR) +0.00 fcntl(3, F_SETFL, O_RDWR | O_NONBLOCK) = 0 +0.00 setsockopt(3, IPPROTO_TCP, TCP_LOG, [4], 4) = 0 +0.00 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) +0.00 > S 0:0(0) win 65535 <mss 1460,nop,wscale 8,sackOK,TS val 100 ecr 0> +0.10 < S. 0:0(0) ack 1 win 32767 <mss 1440,sackOK,TS val 400 ecr 100> +0.00 > . 1:1(0) ack 1 win 65535 <nop,nop,TS val 200 ecr 400> // Change to rack_latest +0.00 setsockopt(3, IPPROTO_TCP, TCP_NODELAY, [1], 4) = 0 +0.00 setsockopt(3, IPPROTO_TCP, TCP_FUNCTION_BLK, {function_set_name="rack", pcbcnt=0}, 36) = 0 +0.00 send(3, ..., 1000, 0) = 1000 +0.00 > P. 1:1001(1000) ack 1 win 65535 <nop,nop,TS val 250 ecr 400> +.10 < . 1:1(0) ack 1001 win 32000 <nop, nop, TS val 500 ecr 250> +0.00 send(3, ..., 1000, 0) = 1000 +0.00 > P. 1001:2001(1000) ack 1 win 65535 <nop,nop,TS val 300 ecr 500> +.10 < . 1:1(0) ack 2001 win 32000 <nop, nop, TS val 600 ecr 300> // cwnd should be 18,280 +0.10 send(3, ..., 25440, 0) = 25440 * > . 2001:3429(1428) ack 1 win 65535 <nop,nop,TS val 400 ecr 600> * > . 3429:4857(1428) ack 1 win 65535 <nop,nop,TS val 500 ecr 600> * > . 4857:6285(1428) ack 1 win 65535 <nop,nop,TS val 600 ecr 600> * > . 6285:7713(1428) ack 1 win 65535 <nop,nop,TS val 700 ecr 600> * > . 7713:9141(1428) ack 1 win 65535 <nop,nop,TS val 800 ecr 600> * > . 9141:10569(1428) ack 1 win 65535 <nop,nop,TS val 900 ecr 600> * > . 10569:11997(1428) ack 1 win 65535 <nop,nop,TS val 900 ecr 600> * > . 11997:13425(1428) ack 1 win 65535 <nop,nop,TS val 1100 ecr 600> * > . 13425:14853(1428) ack 1 win 65535 <nop,nop,TS val 1200 ecr 600> * > . 14853:16281(1428) ack 1 win 65535 <nop,nop,TS val 1300 ecr 600> * > . 16281:17709(1428) ack 1 win 65535 <nop,nop,TS val 1400 ecr 600> // TLP * > . 17709:19137(1428) ack 1 win 65535 <nop,nop,TS val 1500 ecr 600> // TLP * > . 19137:20565(1428) ack 1 win 65535 <nop,nop,TS val 1600 ecr 600> // T-O (cwnd to 1500) * > . 2001:3429(1428) ack 1 win 65535 <nop,nop,TS val 1900 ecr 600> // Send ICMP +0.00 < [2001:3429(1428)] icmp unreachable frag_needed mtu 1200 // Retransmit * > . 2001:3149(1148) ack 1 win 65535 <nop,nop,TS val 2000 ecr 600> * > . 3149:3429(280) ack 1 win 65535 <nop,nop,TS val 2100 ecr 600> +0.10 < . 1:1(0) ack 3429 win 32000 <nop, nop, TS val 700 ecr 2100> // Retransmits of window * > . 3429:4577(1148) ack 1 win 65535 <nop,nop,TS val 2200 ecr 700> * > . 4577:4857(280) ack 1 win 65535 <nop,nop,TS val 2300 ecr 700> // TLP * > . 20565:21713(1148) ack 1 win 65535 <nop,nop,TS val 2400 ecr 700> +.10 < . 1:1(0) ack 21713 win 32000 <nop, nop, TS val 800 ecr 2400> // Tear it down. +0.00 close(3) = 0 * > . 21713:22861(1148) ack 1 win 65535 <nop,nop,TS val 2500 ecr 800> +.00 < . 1:1(0) ack 22861 win 32000 <nop, nop, TS val 900 ecr 2400> * > . 22861:24009(1148) ack 1 win 65535 <nop,nop,TS val 2600 ecr 800> * > . 24009:25157(1148) ack 1 win 65535 <nop,nop,TS val 2700 ecr 800> +.00 < . 1:1(0) ack 25157 win 32000 <nop, nop, TS val 1000 ecr 2700> * > . 25157:26305(1148) ack 1 win 65535 <nop,nop,TS val 2800 ecr 800> * > P. 26305:27441(1136) ack 1 win 65535 <nop,nop,TS val 2900 ecr 1000> +.00 < . 1:1(0) ack 27441 win 32000 <nop, nop, TS val 1100 ecr 2900> +0.00 > F. 27441:27441(0) ack 1 win 65535 <nop,nop,TS val 3000 ecr 1100> +0.10 < F. 1:1(0) ack 27442 win 32767 <nop,nop,TS val 1200 ecr 3000> +0.00 > . 27442:27442(0) ack 2 win 65535 <nop,nop,TS val 3100 ecr 1200> When running the pkt drill you will have to control-c it without the fix and if you have a tcp log dumper deamon the logging output will show you TLP's going by with no output until you stop the test (or pkt drill times out).