doc: ignoring traffic

doc/sphinx/performance/ignoring-traffic.rst

@@ -0,0 +1,46 @@
+Ignoring Traffic
+================
+
+In some cases there are reasons to ignore certain traffic. Maybe a
+trusted host or network, or a site. This document lists some
+strategies for ignoring traffic.
+
+capture filters (BPF)
+---------------------
+
+Through BPFs the capture methods pcap, af-packet and pf_ring can be
+told what to send to Suricata, and what not. For example a simple
+filter 'tcp' will only send tcp packets.
+
+If some hosts and or nets need to be ignored, use something like "not
+(host IP1 or IP2 or IP3 or net NET/24)".
+
+pass rules
+----------
+
+Pass rules are Suricata rules that if matching, pass the packet and in
+case of TCP the rest of the flow. They look like normal rules, except
+that instead of 'alert' or 'drop' they start with 'pass'.
+
+Example:
+
+::
+
+  pass ip 1.2.3.4 any <> any any (msg:"pass all traffic from/to 1.2.3.4"; sid:1;)
+
+A big difference with capture filters is that logs such as http.log
+are still generated for this traffic.
+
+suppress
+--------
+
+Suppress rules can be used to make sure no alerts are generated for a
+host. This is not efficient however, as the suppression is only
+considered post-matching. In other words, Suricata first inspects a
+rule, and only then will it consider per-host suppressions.
+
+Example:
+
+::
+
+  suppress gen_id 0, sig_id 0, track by_src, ip 1.2.3.4

doc/sphinx/performance/index.rst

@@ -10,3 +10,4 @@ Performance
    rule-profiling
    runmodes
    tcmalloc
+   ignoring-traffic