[lwip-devel] [patch #9381] Sending TCP timestamp option in SYN packets

[Jakub Schmidtke]

Follow-up Comment #2, patch #9381 (project lwip):

Doing this only for incoming TCP connections certainly prevents it from being
used by two lwIP instances talking to each other.
However, I feel like the choice for supporting it for incoming connections
only instead of of only for outgoing connections only
(which would also prevent two instances of lwIP using it between each other)
is somewhat arbitrary.
If that's intended, that's fine, but I don't think there is an RFC that would
explain/define that choice made by lwIP developers...

According to RFC 1323 (section 1.3), timestamp option should be only used if
it is included in both initial <SYN> and <SYN,ACK> packets.
This patch adds exactly that behaviour.

If the intent is to avoid a situation where two lwIP instances use this option
while talking to each other,
would it be acceptable if I modified the patch and added a define, making
enabling that option in outgoing <SYN> packets optional?
This way people would be able to choose if they want to have it supported in
both directions while potentially risking
two lwIP instances using it, while not really taking advantage of that, or
stick to current behaviour.

Or, perhaps, a define that enables it only for outgoing connections, but
disables use of that option for incoming connections
(effectively mirror asymmetrical behaviour)? That change would be slightly
bigger.

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