MINOR: mux-h2: count late reduction of INITIAL_WINDOW_SIZE as a glitch

It's quite uncommon for a client to decide to change the connection's
initial window size after the settings exchange phase, unless it tries
to increase it. One of the impacts depending is that it updates all
streams, so it can be expensive, depending on the stacks, and may even
be used to construct an attack. For this reason, we now count a glitch
when this happens.

A test with h2spec shows that it triggers 9 across a full test.

(cherry picked from commit 9f3a0834d8e4c1416c0e266e987d9c0378558659)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit cb7bbada91b2224f58652791ba51ca4e5eb93d8f)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed