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Igalia / pflua

Packet filtering in Lua
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ICMP/ARP discrepency investigation #180

Closed kbara closed 9 years ago

kbara commented 9 years ago

https://github.com/Igalia/pflua/issues/178 mentioned incorrect behaviour with an "icmp or arp" filter. Here is some work towards narrowing down the problem.

The behaviour is packet-dependent. % luajit ./pipe-lua-libpcap-match ../tests/data/arp.pcap "icmp or arp" 1 OK: pure-lua, bfp-lua, and libpcap pipelines matched: all true % luajit ./pipe-lua-libpcap-match ../tests/data/arp.pcap "icmp or arp" 2 BUG: pure-lua false, bpf-lua true, libpcap true.

This falsifies the idea that it's purely due to protocol assertions.

The bug persists with optimization disabled. % luajit -O0 ./pipe-lua-libpcap-match ../tests/data/arp.pcap "icmp or arp" 2 BUG: pure-lua false, bpf-lua true, libpcap true.

This falsifies the idea that it's purely an optimizer bug.

wingo commented 9 years ago

It seems that it is indeed an optimizer bug:

wingo@rusty:~/src/pflua$ ./env tools/pipe-lua-libpcap-match tests/data/arp.pcap 'icmp or arp' 2
BUG: pure-lua false, bpf-lua true, libpcap true.
wingo@rusty:~/src/pflua$ ./env tools/pipe-lua-libpcap-match -O0 tests/data/arp.pcap 'icmp or arp' 2
OK: pure-lua, bfp-lua, and libpcap pipelines matched: all true

Kat's tests passed -O0 to luajit :) Funny bug. I guess the lesson is to always use the env scripts.

kbara commented 9 years ago

Oops. :-)

The root cause was indeed the length hoisting bug, which is now fixed: https://github.com/Igalia/pflua/issues/182 for details.

I'm closing this bug, as we appear to not have any more low-hanging "x or y" bugs, where x and y are protocol names. See https://github.com/Igalia/pflua/pull/183 for details.

while ../tools/pflua-quickcheck properties/pipecmp_proto_or_proto ../tests/data/arp.pcap; do; done and while ../tools/pflua-quickcheck properties/pipecmp_proto_or_proto ../tests/data/wingolog.pcap; do; done are both turning up no counter-examples.