read() returns ETIMEDOUT on steady TCP connection

[Andre Oppermann]

Mark Hills wrote:
> On Wed, 23 Apr 2008, Andre Oppermann wrote:
> 
>> http://people.freebsd.org/~andre/tcp_output-error-log.diff
>>
>> Please apply this patch and enable the sysctl net.inet.tcp.log_debug=1
>> and report any output.  You likely get some (normal) noise from syncache.
>> What we are looking for is reports from tcp_output.
> 
> Hi Andre, I've applied the patch and tested.
> 
> Aside from syncache noise, I get a constant stream of 'error 55' 
> (ENOBUFS?), once the number of connection gets to around 150 at 192kbps.
> 
> TCP: [192.168.5.43]:52153 to [192.168.5.40]:8080; tcp_output: error 55 
> while sending
> 
> 192.168.5.40 is the IP address of this host, running the server.
> 
> I tried to correlate the point of the application receiving ETIMEDOUT 
> with these messages, but that is tricky as it seems to be outputting a 
> lot of messages, and multiple messages over eachother (see below).
> 
> Because of the mention of no buffer space available, I checked the 
> values of net.inet.tcp.sendbuf* and recvbuf*, and increased the max 
> values with no effect.
> 
> When I get time I will modify the kernel to print errors which aren't 
> ENOBUFS to see if there are any others. But in the meantime, this sounds 
> like a problem to me. Is that correct?

Yes.  I'll investigate why you get ENOBUFS here despite your netstat -m
output not showing any request denied.

-- 
Andre

> Mark
> 
> 
> :8080; tcp_output: error 55 while sending
> TCP: [192.168.5.42]:57384T CtPo:  
> [[119922..116688..55..4402]]::85048400;1  ttoc p[_1o9u2t.p1u6t8:. 
> 5e.r4r0o]r: 8080;5 5t cwp_hoiultep uste:n deirnrgor 55 while sending
> TCP: [192.168.5.42]:57382 to [192.168.5.40]:8080; tcp_output: error 55 
> while sending
> TCP: [192.168.5.42]:57381 to [192.168.5.40]:8080; tcp_output: error 55 
> while sending
> TCP: [192.168.5.42]:57380 to [192.168.5.40]:8080; tcp_output: error 55 
> while sending
> 
> 
>