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In Ubuntu docs I saw this sample script which is mentioning netfilter bug:

# Workaround bug in netfilter
-A OUTPUT -m conntrack -p icmp --ctstate INVALID -j DROP

I wonder which bug it's referring and more details on how it will behave without this line

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The following link gives some details:

It seems to be related to errors made by p2p traffic.

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Not so clear what was the problem. – Michael Aug 20 '10 at 10:04

what's the date of the doc ? propably it's something obsolete

share|improve this answer 2009-12-19. Would be glad if someone confirm that it's fixed and I don't need this workaround. – Michael Aug 21 '10 at 0:09

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