tcpdump mailing list archives
Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1
From: Jim Lloyd <jlloyd () silvertailsystems com>
Date: Wed, 25 Aug 2010 08:55:09 -0700
On Wed, Aug 25, 2010 at 2:14 AM, Guy Harris <guy () alum mit edu> wrote:
On Aug 23, 2010, at 3:54 PM, Jim Lloyd wrote:What is the relationship between the socket receive buffer and the mmap buffer? Does the mmap buffer replace the socket receive buffer,Yes.
Cool.
I currently have my primary testing machine configured with net.core.rmem_default = 4194304 net.core.rmem_max = 16777216 Do we expect the rmem_default setting to be significant or not?No.
Yay!
Can you recommend any traffic generators that can provide test traffic with SACKs?Unfortunately, no. (That doesn't mean they don't exist, it just means I don't know what traffic generators are out there, or which of them provide test traffic with SACKs.)
Ok, thanks anyway. FYI I was able to generate some SACKs by sending my test traffic through an open http proxy. I expect the SACKs I generated don't really cover all possible scenarios, but at least I have raised confidence now that we can handle the most common cases.
Is there any way to detect these kinds of drops with Linux? It looks like the receive drops column in /proc/net/dev might be this count. Can you confirm?I was mistaken - on Linux, at least in libpcap 1.1.x, if you're capturing in promiscuous mode, libpcap *does* fetch the drop count from /proc/net/dev and put it into the ps_ifdrop field of the result of pcap_stats(). I don't know why that's restricted to promiscuous mode.
That works for me! Thanks Guy, these answers have been very helpful. -Jim - This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
Current thread:
- pcap_dispatch on linux 2.6 with libpcap 1.1.1 Jim Lloyd (Aug 21)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Guy Harris (Aug 22)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Guy Harris (Aug 22)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Jim Lloyd (Aug 23)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Guy Harris (Aug 25)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Jim Lloyd (Aug 25)
- Re: pcap_dispatch on linux 2.6 with libpcap 1.1.1 Guy Harris (Aug 22)