I find we might miss a return value of ListenerFilter::onAccept(ListenerFilterCallbacks& cb)

See the return type below.

enum class FilterStatus {
  // Continue to further filters.
  Continue,
  // Stop executing further filters.
  StopIteration
};

So it's impossible to express that onAccept find an error.

Currently if a listener filter wants to report an error, it must

• return StopIteration at onAccept
• register an event
• the callback of the above event call cb.continueFilterChain

The drawback of this detour is that we have to report that error at the second event cycle.
What's worse, as long as it potentially report error, we have to wait another event cycle. See

I am proposing

add a FilterStatus::Error

allow onAccept return it, and handle this value in ActiveSocket::continueFilterChain

Alternatively, since the FilterStatus type is also used by NetworkFilter, we can let onAccept return a new ListenerFilterStatus and only add Error here.

The benefits: we can save one epoll cycle on tls_inspector and http_inspector each, every time a connection is connected on listener which owns such filter.

@lizan @PiotrSikora thoughts?