network problems?

Krassimir Slavchev krassi at
Fri Apr 20 07:17:22 UTC 2007

Peter Jeremy wrote:
> On 2007-Apr-19 11:43:05 +0300, Krassimir Slavchev <krassi at> wrote:
>> The problem is when I try to access ftp servers, the connection stalls 
>> randomly. Also I can't do cvsup and fetch.
>> This happens only with machines running -current and when the traffic is 
>> passed through router based on FreeBSD 4.4. One of the test machines is 
>> my notebook which have installed 7.0-CURRENT (from today) and 5.4-STABLE 
>> and I see this problem only with -current.
> The default TCP send and receive spaces were increased just after
> RELENG4 was branched.  The new receive space requires window scaling
> to be used.  I know that some versions of IPfilter have bugs in their
> window scaling code and incorrectly block packets as "out of window".
> You could try reducing net.inet.tcp.recvspace or disabling
> net.inet.tcp.rfc1323 and see if that helps.  (Though RELENG5 should
> also be affected if this is the problem).
Disabling net.inet.tcp.rfc1323 solves the problem. Decreasing 
net.inet.tcp.recvspace (16384 on 4.x) increases stallages.

> Are you in a position to run tcpdump on your router?  If so, can you
> tcpdump both the internal and external interfaces and find packets
> that don't make it thru?
Yes. I can do this when the traffic is minimal.

It is very strange that both 6.2 and 5.4 have the same settings as 7.0:

net.inet.tcp.recvspace: 65536
net.inet.tcp.rfc1323: 1

but the problem is with 7.0 only.

Best Regards

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