On Mon, Jun 9, 2008 at 9:06 AM, B A <openbsd-ab@ya.ru> wrote:
quoted text > bash-3.2# pfctl -sr
> scrub all no-df random-id max-mss 1400 fragment reassemble
> pass in quick all flags S/SA keep state
> pass out quick all flags S/SA keep state
quoted text > Ok. Here is openbsd tcpdump. But I still see len 1440 packets.
>
> 03:57:54.035986 192.168.133.200.9901 > 192.168.133.1.80: S [tcp sum ok] 1790495358:1790495358(0) win 16384 <mss 1400,nop,nop,sackOK,nop,wscale 0,nop,nop,timestamp 3743718606 0> (ttl 64, id 55493, len 64)
> 03:57:54.036047 192.168.133.1.80 > 192.168.133.200.9901: S [tcp sum ok] 2480387518:2480387518(0) ack 1790495359 win 5792 <mss 1460,sackOK,timestamp 343617 3743718606,nop,wscale 7> (DF) (ttl 64, id 0, len 60)
> 03:57:54.036080 192.168.133.200.9901 > 192.168.133.1.80: . [tcp sum ok] ack 1 win 16384 <nop,nop,timestamp 3743718606 343617> (ttl 64, id 40579, len 52)
> 03:57:54.036210 192.168.133.200.9901 > 192.168.133.1.80: P 1:70(69) ack 1 win 16384 <nop,nop,timestamp 3743718606 343617> (ttl 64, id 7424, len 121)
> 03:57:54.036257 192.168.133.1.80 > 192.168.133.200.9901: . [tcp sum ok] ack 70 win 46 <nop,nop,timestamp 343617 3743718606> (DF) (ttl 64, id 35838, len 52)
> 03:57:54.040971 192.168.133.1.80 > 192.168.133.200.9901: P 1:229(228) ack 70 win 46 <nop,nop,timestamp 343617 3743718606> (DF) (ttl 64, id 35839, len 280)
> 03:57:54.040976 192.168.133.1.80 > 192.168.133.200.9901: . 229:1617(1388) ack 70 win 46 <nop,nop,timestamp 343617 3743718606> (DF) (ttl 64, id 35840, len 1440)
> 03:57:54.040979 192.168.133.1.80 > 192.168.133.200.9901: . 1617:3005(1388) ack 70 win 46 <nop,nop,timestamp 343617 3743718606> (DF) (ttl 64, id 35841, len 1440)
You might want to read up on packet structures as this is working as
expected. The header of a TCP packet is normally 40 bytes--so you're
seeing a maximum MSS of 1400 bytes and an MTU of 1440 bytes.
