Red Hat Bugzilla – Bug 137555
loopback adapter fails to send packets over 15984 bytes large
Last modified: 2007-11-30 17:07:04 EST
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Description of problem:
I was having problems with Cups not sending printjobs over a certain
size. From a lot of tracing I noticed that certain packets just seemed
to disappear, with the data staying in the writeq of the sending process.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
I tested this with the 'sock' program from stevens' TCP/IP illustrated
vol 1, found at:
unpack the tarball; ./configure
vi unp.h and remove the in_pktinfo struct (it's in the kernel headers).
now open two terminals. In one, do:
strace ./sock -s -U 127.0.0.1 3457
This means: start a server, make it SO_REUSEADDR on that address/port
in the other, do:
strace ./sock -i -w 15984 -p 100 127.0.0.1 3457
Which means: send a test pattern in 15984 bytes size parts with 100 ms
in between to that server
You will see that it connects, then sends packets with some pattern in
them to the other size. Press break and both programs will end.
Start them again, but now with 15985 instead of 15984. You will see
that the packets queue up in the sending program. They never get to
Actual Results: data stays on the sending side.
Expected Results: data goes over the connection to the receiving side.
Testing by comparing the output of iptables-save -c before and after
sending shows that no packets are being blocked, only counters with
ACCEPT targets change.
Hello? Anyone home? Is this a supported version of RedHat?
This bug is filed against RHEL 3, which is in maintenance phase.
During the maintenance phase, only security errata and select mission
critical bug fixes will be released for enterprise products. Since
this bug does not meet that criteria, it is now being closed.
For more information of the RHEL errata support policy, please visit:
If you feel this bug is indeed mission critical, please contact your
support representative. You may be asked to provide detailed
information on how this bug is affecting you.
I'd like to note that this rediculous approach of support of a paid-for product by RedHat has (about a year
ago) made me decide never to use, buy or recommend any product from RedHat ever again. Goodbye!