read() returns ETIMEDOUT on steady TCP connection

[Mark Hills]

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?

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