accf_http and incqlen

Scott Oertel freebsd at
Wed Mar 5 16:08:39 UTC 2008

I setup the http accept filter with apache and I was having a hard time
understanding this, maybe you guys could help out.

I've tested this among various version of freebsd, and with various
apache configs, and it appears to behave the same across the board.

So why is it that it "appears" that the TCP connections never terminate,
just stay in a state of ESTABLISHED, and why doesn't this queue ever
flush itself, is it normal, if it is, what happens exactly when the
queue fills up to maxqlen. From the netstat output below, you can see
that the incqlen is maxed out. I've done quite a bit of searching
regarding this queue but haven't found any real solid information which
describes what happens when it fills up, and at the same time this is
going on, I have 517 established connections to port 80.

]# netstat -an|grep "\.80"|grep ESTAB|wc -l

]# netstat -Lan

Current listen queue sizes (qlen/incqlen/maxqlen)
Proto Listen         Local Address
tcp4  0/0/5          *.8080
tcp4  0/510/511      *.80
tcp4  0/0/10         *.587
tcp4  0/0/10         *.25
tcp4  0/0/128        *.22
tcp4  0/0/100        *.3306
tcp4  0/0/9          *.21
tcp4  0/0/128
tcp4  0/0/3

-Scott Oertel

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