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ctl_enqueuedata() woes

Subject: ctl_enqueuedata() woes
From: "Karl Pickett" <email@hidden>
Date: Wed, 3 Oct 2007 12:26:25 -0400
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I have modified the tcplognke example and it was pleasant sailing until now. I am sending packets to userspace that are about 2020 bytes long. Userspace reads each packet and responds with a setsockopt() call with a 2k structure.

When a burst of packets gets sent, some packets will fail to be received by user space but no error was indicated from ctl_enqueuedata()

Calling ctl_getenqueuespace(), the packets end up disappearing when ever the queuespace is not the maximum. Bumping up the socket recvbuf from 8k to 60k did not help one bit!

An example where I bumped the rcv_buff up to 60000:

Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 35: ret 0, space=60000
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 36: ret 0, space=57924
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 37: ret 0, space=55848
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 38: ret 0, space=53772
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 39: ret 0, space=51696
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 40: ret 0, space=49620
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 41: ret 0, space=47544
Oct 2 17:16:21 karls-power-mac-g4 kernel[0]: ctl_enqueuedata 42: ret 0, space=60000

Only packets 35 and 42 were received by userspace! The rest went to a bit bucket somewhere, and as you can see the ret 0 indicates no error by ctl_enqueuedata. In some cases when the space was completely exhausted ctl_enqueuedata would return an error, but otherwise the packets would just disappear when ever the enqueuespace was not at max.

--
Karl Pickett
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -- Benjamin Franklin

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