On Thu, 2014-04-03 at 21:36 -0700, Ben Greear wrote:
> I don't know any off-the-shelf software that supports setting TCP MSS,
> but maybe iperf or similar can either do it now or can be modified
> to make it support that feature.
>
> If you don't have anything that reproduces this easily, let me know and I'll
> hack iperf or something similar and get a reproducible test case for you.
You can use ip ro .... advmss 256
lpi25:~# ip ro get 7.7.7.27
7.7.7.27 dev eth2 src 7.7.7.25
cache
lpi25:~# ip ro add 7.7.7.27 dev eth2 advmss 256
Launch iperf/netperf and check with tcpdump :
lpi25:~# tcpdump -p -n -s 128 -i eth2 -c 30
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth2, link-type EN10MB (Ethernet), capture size 128 bytes
21:55:56.479729 IP 7.7.7.27.48333 > 7.7.7.25.12865: S 1458993514:1458993514(0)
win 29200 <mss 1460,sackOK,timestamp 192333880 0,nop,wscale 6>
21:55:56.479793 IP 7.7.7.25.12865 > 7.7.7.27.48333: S 2807738316:2807738316(0)
ack 1458993515 win 4880 <mss 256,sackOK,timestamp 183391 192333880,nop,wscale 6>
21:55:56.479804 IP 7.7.7.27.48333 > 7.7.7.25.12865: . ack 1 win 457
<nop,nop,timestamp 192333880 183391>
21:55:56.479180 IP 7.7.7.27.48333 > 7.7.7.25.12865: . 1:245(244) ack 1 win 457
<nop,nop,timestamp 192333881 183391>
21:55:56.479816 IP 7.7.7.25.12865 > 7.7.7.27.48333: . ack 245 win 84
<nop,nop,timestamp 183391 192333881>
21:55:56.479192 IP 7.7.7.27.48333 > 7.7.7.25.12865: P 245:657(412) ack 1 win
457 <nop,nop,timestamp 192333881 183391>
21:55:56.479827 IP 7.7.7.25.12865 > 7.7.7.27.48333: . ack 657 win 97
<nop,nop,timestamp 183391 192333881>
21:55:56.479562 IP 7.7.7.25.12865 > 7.7.7.27.48333: P 1:657(656) ack 657 win 97
<nop,nop,timestamp 183391 192333881>
21:55:56.479684 IP 7.7.7.27.48333 > 7.7.7.25.12865: . ack 657 win 477
<nop,nop,timestamp 192333881 183391>
21:55:56.479925 IP 7.7.7.27.48333 > 7.7.7.25.12865: . 657:901(244) ack 657 win
477 <nop,nop,timestamp 192333881 183391>
21:55:56.479934 IP 7.7.7.27.48333 > 7.7.7.25.12865: P 901:1313(412) ack 657 win
477 <nop,nop,timestamp 192333881 183391>
21:55:56.479938 IP 7.7.7.25.12865 > 7.7.7.27.48333: . ack 1313 win 118
<nop,nop,timestamp 183392 192333881>
21:55:56.480955 IP 7.7.7.25.12865 > 7.7.7.27.48333: P 657:1313(656) ack 1313
win 118 <nop,nop,timestamp 183393 192333881>
21:55:56.481060 IP 7.7.7.27.34752 > 7.7.7.25.48032: S 4002131517:4002131517(0)
win 29200 <mss 1460,sackOK,timestamp 192333882 0,nop,wscale 6>
21:55:56.481067 IP 7.7.7.25.48032 > 7.7.7.27.34752: S 1423693622:1423693622(0)
ack 4002131518 win 4880 <mss 256,sackOK,timestamp 183393 192333882,nop,wscale 6>
21:55:56.481124 IP 7.7.7.27.34752 > 7.7.7.25.48032: . ack 1 win 457
<nop,nop,timestamp 192333882 183393>
21:55:56.481168 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 1:2197(2196) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481173 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 2197:2441(244) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481175 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 2197 win 145
<nop,nop,timestamp 183393 192333883>
21:55:56.481179 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 2441 win 153
<nop,nop,timestamp 183393 192333883>
21:55:56.481221 IP 7.7.7.27.34752 > 7.7.7.25.48032: P 2441:4881(2440) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481226 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 4881 win 229
<nop,nop,timestamp 183393 192333883>
21:55:56.481228 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 4881:6101(1220) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481235 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 6101 win 267
<nop,nop,timestamp 183393 192333883>
21:55:56.481238 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 6101:7321(1220) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481244 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 7321 win 305
<nop,nop,timestamp 183393 192333883>
21:55:56.481246 IP 7.7.7.27.34752 > 7.7.7.25.48032: P 7321:9761(2440) ack 1 win
457 <nop,nop,timestamp 192333883 183393>
21:55:56.481251 IP 7.7.7.25.48032 > 7.7.7.27.34752: . ack 9761 win 382
<nop,nop,timestamp 183393 192333883>
21:55:56.481254 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 9761:11957(2196) ack 1
win 457 <nop,nop,timestamp 192333883 183393>
21:55:56.481260 IP 7.7.7.27.34752 > 7.7.7.25.48032: . 11957:12201(244) ack 1
win 457 <nop,nop,timestamp 192333883 183393>
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