XPost: comp.os.linux.networking   
   From: markhobley@yahoo.donottypethisbit.co   
      
   On Sun, 22 May 2011 11:31:25 +0000, Jorgen Grahn wrote:   
      
   > On Sun, 2011-05-22, Mark Hobley wrote: ...   
   >> I'll try dropping another 12 bytes off the ip route command and retest:   
   >>   
   >> ip route change default via 10.0.0.1 mtu lock 1400   
   >>   
   >> Am I right in that the below datagram is wrong, because the mss is   
   >> 1460, which is above the value of the mtu in the routing table?   
   >> Shouldn't the value of the mtu have been factored in here, and a new   
   >> mss calculated based on the mtu?   
   >>   
   >> 03:43:04.320740 IP venus.markhobley.yi.org.52201 >   
   >> news.eternal-september.org.nntp: Flags [S], seq 2304145392, win 14600,   
   >> options [mss 1460,sackOK,TS val 47122576 ecr 0,nop,wscale 5], length 0   
   >   
   > Yes, that seems wrong too. I have only messed with that once, as an   
   > experiment, but I am pretty sure my TCP stack understood it and set mss   
   > in the SYN accordingly. (I used 'route ... mss N' to do it, not ip(8),   
   > but that shouldn't matter.)   
      
   Hmmm. So if the datagram is wrong, then we have a bug. Presumably this is   
   a kernel bug, because it has been working for a couple of months before I   
   upgraded the kernel. Or could it be a library bug? I might have upgraded   
   some libraries, for the purpose of being able to use the new kernel.   
      
   Mark.   
      
   --   
   Mark Hobley   
   Linux User: #370818  http://markhobley.yi.org/   
      
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