tcp failing to recover from a packet loss under 8.2-RELEASE?

[Steven Hartland]

----- Original Message ----- 
From: "Andre Oppermann" <andre at freebsd.org>
...
>> I believe this is tcps_rcvmemdrop in tcp_reass.c to which there's the
>> following comment:-
>>
>> * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
>> * should work but causes packets to be dropped when they shouldn't.
>>
>> I notice this code is relatively new, so I'm wondering if this may be
>> something to do with what we're seeing, possibly still dropping packets
>> it shouldn't?
>>
>> @Lawrence apologies' for the direct mail, but I believe you where the
>> original author this particular change so wondered if you may be
>> able to shed any light on this?
>
> You could be onto something here. Please try this patch:
>  http://people.freebsd.org/~andre/tcp_reass.c-logdebug-20110802.diff
>
> You can enable the log output with
>  sysctl net.inet.tcp.log_debug=1
> and report the log output (comes at LOG_DEBUG level).

Thanks for the response Andre, I've applied the patch and I'm seeing
lots of the following during the test which is:-
1. scp from local host (10.10.1.30) -> tcptest (10.10.1.20) reciever
   which gets ~ 64MB/s
2. scp from remote host (10.10.1.10) -> tcptest (10.10.1.20) reciever
   which gets ~ 10MB/s (line has packet loss)

Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped, would have drained queue!
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped, would have drained queue!
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.10]:32416 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped, would have drained queue!
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped, would have drained queue!
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped
Aug  2 11:08:50 tcptest kernel: TCP: [10.10.1.30]:60811 to [10.10.1.20]:22 tcpflags 0x10<ACK>; tcp_reass: global zone limit 
reached, segment dropped

    Regards
    Steve 


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