All TCP ISNs that are sent out are valid cookies, which allows entries
in the syncache to be dropped and still have the ACK accepted later.
As all entries pass through the syncache, there is no sudden switchover
from cache -> cookies when the cache is full; instead, syncache entries
simply have a reduced lifetime. More details may be found in the
"Resisting DoS attacks with a SYN cache" paper in the Usenix BSDCon 2002
conference proceedings.
Sponsored by: DARPA, NAI Labs
receiver was not sending an immediate ack with delayed acks turned on
when the input buffer is drained, preventing the transmitter from
restarting immediately.
Propogate the TCP_NODELAY option to accept()ed sockets. (Helps tbench and
is a good idea anyway).
Some cleanup. Identify additonal issues in comments.
MFC after: 1 day
to be followed by nfsnodehashtbl, so bzeroing callouts beyond the end of
tcp_syncache soon caused a null pointer panic when nfsnodehashtbl was
accessed.
