With the recent changes db36d948fa, we try
to balance the receive window advertisements between payload lengths vs
segment overhead length. This works fine when segment size are much
higher than the overhead, but not otherwise. In cases where the segment
length is smaller than the segment overhead, we may end up not
advertising zero receive window for long time and end up tail-dropping
segments. This is especially pronounced when application socket reads
are slow or stopped. In this change we do not grow the right edge of
the receive window for smaller segment sizes similar to Linux.
Also, we keep track of the socket buffer usage and let the window grow
if the application is actively reading data.
Fixes#4903
PiperOrigin-RevId: 345832012
TCP now tracks the overhead of the segment structure itself in it's out-of-order
queue (pending). This is required to ensure that a malicious sender sending 1
byte out-of-order segments cannot queue like 1000's of segments which bloat up
memory usage.
We also reduce the default receive window to 32KB. With TCP moderation there is
no need to keep this window at 1MB which means that for new connections the
default out-of-order queue will be small unless the application actually reads
the data that is being sent. This prevents a sender from just maliciously
filling up pending buf with lots of tiny out-of-order segments.
PiperOrigin-RevId: 323450913
Mithun Iyer
Bhasker Hariharan