tcpdump mailing list archives
TPACKET_V3 support added big packet delivery delay and/or affected timestamps
From: Thomas Habets <thomas () habets se>
Date: Thu, 4 Dec 2014 18:13:14 +0000
Affected releases: 1.5.0 and up. Steps to reproduce: git checkout -f libpcap-1.5.0 ./configure --prefix=/opt/badpcap && make && make install git clone github.com/ThomasHabets/arping cd arping ./boostrap.sh ./configure && make LD_PRELOAD=/opt/badpcap/lib/libpcap.so ./src/arping your.local.next.hop Actual behaviour: $ sudo sh -c "LD_PRELOAD=$HOME/opt/buggypcap/lib/libpcap.so ./arping 10.0.0.1" ARPING 10.0.0.1 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=0 time=52.633 msec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=1 time=90.928 msec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=2 time=115.183 msec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=3 time=285.153 msec ^C --- 10.0.0.1 statistics --- 4 packets transmitted, 4 packets received, 0% unanswered Expected (and received with 1.4.0): $ sudo sh -c "LD_PRELOAD=$HOME/opt/goodpcap/lib/libpcap.so ./arping 10.0.0.1" ARPING 10.0.0.1 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=0 time=817.060 usec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=1 time=895.977 usec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=2 time=759.840 usec 60 bytes from 00:xx:xx:xx:xx:xx (10.0.0.1): index=3 time=827.074 usec ^C --- 10.0.0.1 statistics --- 4 packets transmitted, 4 packets received, 0% unanswered Notice the unit difference. About a hundred milliseconds vs about 800 microseconds. What appears to be the relevant commit: https://github.com/the-tcpdump-group/libpcap/commit/8ada1d5b98ac62c4ae9acbecb0639beeebd8a359 Questions: Is TPACKET V3 (and V2?) much slower than V1? Can I disable them? Is this actual delay, or just a different way of measuring? -- typedef struct me_s { char name[] = { "Thomas Habets" }; char email[] = { "thomas () habets pp se" }; char kernel[] = { "Linux" }; char *pgpKey[] = { "http://www.habets.pp.se/pubkey.txt" }; char pgp[] = { "A8A3 D1DD 4AE0 8467 7FDE 0945 286A E90A AD48 E854" }; char coolcmd[] = { "echo '. ./_&. ./_'>_;. ./_" }; } me_t; _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- TPACKET_V3 support added big packet delivery delay and/or affected timestamps Thomas Habets (Dec 04)
- Re: TPACKET_V3 support added big packet delivery delay and/or affected timestamps Guy Harris (Dec 04)
- Re: TPACKET_V3 support added big packet delivery delay and/or affected timestamps Thomas Habets (Dec 05)
- Re: TPACKET_V3 support added big packet delivery delay and/or affected timestamps Guy Harris (Dec 04)