In the case where DNS requests are sent over the same flow w/o a
reply being received, we now set an event in the flow and refuse
to add more transactions to the state. This protects the DNS
handling from getting overloaded slowing down everything.
A new option to configure this behaviour was added:
app-layer:
protocols:
dnsudp:
enabled: yes
detection-ports:
udp:
toserver: 53
request-flood: 750
The request-flood parameter can be 0 (disabling this feature) or a
positive integer. It defaults to 500.
This means that if 500 unreplied requests are seen in a row an event
is set. Rule 2240007 was added to dns-events.rules to match on this.