Add keepalive_tolerance http2 option

The number of unacknowledged pings that can be tolerated
before the connection is forcefully closed.

When a keepalive ping is sent to the peer, a counter is
incremented and if this counter exceeds the tolerance limit,
the connection is forcefully closed. The counter is
decremented whenever a ping ack is received from the peer.

By default, the mechanism for closing the connection based
on ping and ping ack is disabled.

Loïc Hoguin: I have edited a lot of the code and renamed
a few things as well as simplified the docs and increased
test timeouts to avoid race conditions.

1 files changed, 8 insertions, 0 deletions

diff --git a/doc/src/manual/gun.asciidoc b/doc/src/manual/gun.asciidoc
index 40559fb..d511fdc 100644
--- a/doc/src/manual/gun.asciidoc
+++ b/doc/src/manual/gun.asciidoc
@@ -209,6 +209,7 @@ http2_opts() :: #{
     cookie_ignore_informational => boolean(),
     flow                        => pos_integer(),
     keepalive                   => timeout(),
+    keepalive_tolerance         => non_neg_integer(),
 
     %% HTTP/2 state machine configuration.
     connection_window_margin_size  => 0..16#7fffffff,
@@ -257,6 +258,13 @@ keepalive (infinity)::
 
 Time between pings in milliseconds.
 
+keepalive_tolerance - see below::
+
+The number of unacknowledged pings in flight that are
+tolerated before the connection is closed. By default
+this mechanism is disabled even if `keepalive` is
+enabled.
+
 === opts()
 
 [source,erlang]