Avoid using libpcap on Linux

[rlane]

Reviewer: @jnealtowns

Starting with Ubuntu 14.04 libpcap uses the TPACKET_V3 interface to receive packets. TPACKET_V3 is unsuitable for applications with low packet rates that want to receive packets immediately. Newer versions of libpcap have an API pcap_set_immediate_mode that reverts to using TPACKET_V2. However, I couldn't find any pcap Python libraries on pip that supported this call. The pypcap package we use is unmaintained, so we can't just add it. My personal workaround of downgrading libpcap isn't scalable.

The original reason we started using libpcap was that it handled VLAN offload and reconstructed the offloaded tag in the packet data. This isn't easy to do in pure Python because the offloaded tag is delivered in a recvmsg control message, but at this point it's easier than fixing pypcap.

[jnealtowns]

ACK

[bsn-abat]

ABAT: START_MERGE: Log file at http://vbs22/abat/2015.03.18.2019-m.oftest.master/abat.log

[bsn-abat]

ABAT: AUTO-REJECT: Your change failed pre-merge validation defined in oftest/.abat-automerge. See log for details.

INSTRUCTIONS: Please fix your problem by

1. Reviewing the logs below and git commiting a fix.

2. Use git push to add new commits to this same remote branch/pull request.

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Log file at http://vbs22/abat/2015.03.18.2019-m.oftest.master/abat.log
/cc

[rlane]

RETRY

[bsn-abat]

ABAT: START_MERGE: Log file at http://vbs22/abat/2015.03.18.2042-m.oftest.master/abat.log

[bsn-abat]

ABAT: AUTO-REJECT: Your change failed pre-merge validation defined in oftest/.abat-automerge. See log for details.

INSTRUCTIONS: Please fix your problem by

1. Reviewing the logs below and git commiting a fix.

2. Use git push to add new commits to this same remote branch/pull request.

3. Get another code review approval from your co-worker indicated by a line of "ACK" in comment, or add another comment yourself with a line of "R_E_T_R_Y (Remove the underscores)". That will cause abat to try to merge your code again.

Log file at http://vbs22/abat/2015.03.18.2042-m.oftest.master/abat.log
/cc

[rlane]

RETRY

[bsn-abat]

ABAT: START_MERGE: Log file at http://vbs21/abat/2015.03.18.2106-m.oftest.master/abat.log

[bsn-abat]

ABAT: ACCEPT: Successfully merged

In case you want to see the build log, check out :
Log file at http://vbs21/abat/2015.03.18.2106-m.oftest.master/abat.log
/cc