a few new wrinkles for MTU discovery which tcp_output() had better
be prepared to handle. ip_output() is also modified to do something
helpful in this case, since it has already calculated the information
we need.
turned out not to be necessary; simply watching for MTU decreases (which
we already did) automagically eliminates all the cases we were trying to
protect against.
middle of a fully-open window. Also, keep track of how many retransmits
we do as a result of MTU discovery. This may actually do more work than
necessary, but it's an unusual condition...
Suggested by: Janey Hoe <janey@lcs.mit.edu>
and gated on `options MTUDISC' in the source. It is also practically
untested becausse (sniff!) I don't have easy access to a network with
an MTU of less than an Ethernet. If you have a small MTU network,
please try it and tell me if it works!
know better when to cache values in the route, rather than relying on a
heuristic involving sequence numbers that broke when tcp_sendspace
was increased to 16k.
its connection parameters, we want to keep statistics on how often this
actually happens to see whether there is any work that needs to be done in
TCP itself.
Suggested by: John Wroclawski <jtw@lcs.mit.edu>
Bob Braden <braden@isi.edu>.
NB: This has not had David's TCP ACK hack re-integrated. It is not clear
what the correct solution to this problem is, if any. If a better solution
doesn't pop up in response to this message, I'll put David's code back in
(or he's welcome to do so himself).
