Feature #3131
closed
EthernetTransport: re-enable TPACKET_V3 for capture if kernel and libpcap are recent enough
Added by Davide Pesavento over 9 years ago.
Updated over 6 years ago.
Description
We disabled TPACKET_V3 in #1511 as a workaround for a Linux kernel bug. The bug was finally fixed in Linux v3.19, released earlier this year. Recently libpcap also received some patches to improve its behavior with TPACKET_V3 and recent kernels.
We should detect if the system has a recent enough combination of kernel and libpcap, and stop disabling TPACKET_V3 in that case. This should improve the performance of the EthernetTransport receive path, and might help with #2441.
- Related to Bug #1511: EthernetFace cannot receive on Ubuntu 14.04 added
- Description updated (diff)
- Subject changed from EthernetFace: re-enable TPACKET_V3 for capture if kernel and libpcap are recent enough to EthernetTransport: re-enable TPACKET_V3 for capture if kernel and libpcap are recent enough
- Target version set to v0.5
Ubuntu would have recent enough libpcap since 15.10.
- Tracker changed from Task to Feature
- Target version deleted (
v0.5)
Junxiao Shi wrote:
Ubuntu would have recent enough libpcap since 15.10.
libpcap version 1.5.3 should be sufficient. And that version is available in Ubuntu 14.04.
- Description updated (diff)
- Status changed from New to Rejected
- Assignee deleted (
Davide Pesavento)
Actually, libpcap recommends enabling immediate mode (thereby limiting the highest TPACKET version to V2) if the application wishes to be notified of new packets as soon as they are received, see https://github.com/the-tcpdump-group/libpcap/issues/472#issuecomment-169791537
The alternative (i.e. allowing TPACKET_V3 by not enabling immediate mode) means setting the "packet buffer timeout" to 1ms (the lowest possible value), which means that each incoming packet may be delayed by up to 1ms, which is probably unacceptable for a packet forwarder. So I'm rejecting this issue.
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