I would appreciate it if you could elaborate on the security issue. Can you
describe the simultaneous connect scenario?
We have a system we are migrating to Linux from Lynx. We have always had the
ability to re-use ports. We are wondering if this security issue is something we
should take seriously. Or, maybe it is not likely to be seen with our system
running well defined set of applications (i.e. not a PC where anybody could run
On Thu, 13 Mar 2008 14:18:15 -0500
See RFC 793. It is permissible for a connection to be created between two
end points both making a connection (crossing SYN frames are both
acked). Thus if you allow such reuse it is possible (although usually
very very hard) to mount a timing based attack.
It's not a very practical attack in most scenarios so we block it out of
correctness and concerns for completely robust and proper behaviour
rather than because it is seen in the wild.