Ethereal-users: [Ethereal-users] OT: mss value = 40

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From: Joshua Banks <l0f33t@xxxxxxxxx>
Date: Sat, 20 Dec 2003 18:55:40 -0800 (PST)
Hello,

This is off topic but I was hoping that maybe someone from this list
could help confirm or explain my problem below.
I'm trying to track down wether or not I have a weird kernel bug.

I'm running Gentoo Linux. 
Kernel version 2.4.20-gentoo-r7
Ehtereal version 0.9.16

When I do either "netstat -rn" or "router -nee" my MSS value shows up
as "40".
root@deadmeat servers # netstat -r -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window 
irtt Iface
63.187.254.9    0.0.0.0         255.255.255.255 UH       40 0         
0 ppp0
192.168.1.0     0.0.0.0         255.255.255.0   U        40 0         
0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U        40 0         
0 eth1
127.0.0.0       127.0.0.1       255.0.0.0       UG       40 0         
0 lo
0.0.0.0         63.187.254.9    0.0.0.0         UG       40 0         
0 ppp0


Yet when I use ethereal I cleary see that my MSS value advertised in
the intial 3 way tcp handshake is my MTU -40. (Which I believe is the
RFC 1122 standard). So for the standard ehternet MTU of 1500 I
consistently see and MSS value of 1460 advertised when I look in
ehtereal. (Which by RFC standards is correct) Yet my routing table
shows "40" under the "MSS" heading. I'm I the only one getting this
weird value?
What "mss values" do you get when issuing the commands above.

Thanks,
Joshua Banks

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