tcpdump mailing list archives
Re: [long] "bad cksum 0!" on AIX 5 over loopback
From: Guy Harris <guy () alum mit edu>
Date: Wed, 2 Jul 2003 17:14:11 -0700
On Wednesday, July 2, 2003, at 4:30 PM, Shaun wrote:
That one is a mystery, it appears to be some sort of kernel issue with uiomove(), I tried to determine what was going on, but gave up when Ifound that memset()ing the buffer to 0 before using it made the problem goaway.
Did that make it go away completely, or did it still occur on occasion? The comment after "case EFAULT:" says
* * For some unknown reason the uiomove() * operation in the bpf kernel extension * used to copy the buffer into user* space sometimes returns EFAULT. I have * no idea why this is the case given that * a kernel debugger shows the user buffer
* is correct. This problem appears to * be mostly mitigated by the memset of * the buffer before it is first used. * Very strange.... Shaun Clowes * but the comment before the memset says /* For some strange reason this seems to prevent the EFAULT * problems we have experienced from AIX BPF. */
You should also note that the AIX bpf driver is buggy and may CRASH YOUR MACHINE, do not use it in production. IBM have recently fixed the problemsand tell me a new version should be released around half way through August.
Have they fixed the EFAULT problem too? - This is the TCPDUMP workers list. It is archived at http://www.tcpdump.org/lists/workers/index.html To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe
Current thread:
- [long] "bad cksum 0!" on AIX 5 over loopback alex medvedev (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Shaun (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Guy Harris (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Shaun (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Guy Harris (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Guy Harris (Jul 02)
- Re: [long] "bad cksum 0!" on AIX 5 over loopback Shaun (Jul 02)