man: Add a man page for the simple action

Signed-off-by: Phil Sutter <phil@nwl.cc>

man/man8/tc-simple.8

+.TH "Simple action in tc" 8 "12 Jan 2015" "iproute2" "Linux"
+
+.SH NAME
+simple - basic example action
+.SH SYNOPSIS
+.in +8
+.ti -8
+.BR tc " ... " "action simple"
+.I STRING
+.SH DESCRIPTION
+This is a pedagogical example rather than an actually useful action. Upon every access, it prints the given
+.I STRING
+which may be of arbitrary length.
+.SH OPTIONS
+.TP
+.I STRING
+The actual string to print.
+.SH EXAMPLES
+The following example makes the kernel yell "Incoming ICMP!" every time it sees
+an incoming ICMP on eth0. Steps are:
+.IP 1) 4
+Add an ingress qdisc point to eth0
+.IP 2) 4
+Start a chain on ingress of eth0 that first matches ICMP then invokes the
+simple action to shout.
+.IP 3) 4
+display stats and show that no packet has been seen by the action
+.IP 4) 4
+Send one ping packet to google (expect to receive a response back)
+.IP 5) 4
+grep the logs to see the logged message
+.IP 6) 4
+display stats again and observe increment by 1
+
+.RE
+.EX
+  hadi@noma1:$ tc qdisc add dev eth0 ingress
+  hadi@noma1:$tc filter add dev eth0 parent ffff: protocol ip prio 5 \\
+	 u32 match ip protocol 1 0xff flowid 1:1 action simple "Incoming ICMP"
+
+  hadi@noma1:$ sudo tc -s filter ls  dev eth0 parent ffff:
+   filter protocol ip pref 5 u32
+   filter protocol ip pref 5 u32 fh 800: ht divisor 1
+   filter protocol ip pref 5 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1
+     match 00010000/00ff0000 at 8
+	action order 1: Simple <Incoming ICMP>
+	 index 4 ref 1 bind 1 installed 29 sec used 29 sec
+	 Action statistics:
+		Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
+		backlog 0b 0p requeues 0
+
+
+  hadi@noma1$ ping -c 1 www.google.ca
+  PING www.google.ca (74.125.225.120) 56(84) bytes of data.
+  64 bytes from ord08s08-in-f24.1e100.net (74.125.225.120): icmp_req=1 ttl=53 time=31.3 ms
+
+  --- www.google.ca ping statistics ---
+  1 packets transmitted, 1 received, 0% packet loss, time 0ms
+  rtt min/avg/max/mdev = 31.316/31.316/31.316/0.000 ms
+
+  hadi@noma1$ dmesg | grep simple
+  [135354.473951] simple: Incoming ICMP_1
+
+  hadi@noma1$ sudo tc/tc -s filter ls  dev eth0 parent ffff:
+  filter protocol ip pref 5 u32
+  filter protocol ip pref 5 u32 fh 800: ht divisor 1
+  filter protocol ip pref 5 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1
+    match 00010000/00ff0000 at 8
+	action order 1: Simple <Incoming ICMP>
+	 index 4 ref 1 bind 1 installed 206 sec used 67 sec
+	Action statistics:
+	Sent 84 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)
+	backlog 0b 0p requeues 0
+.EE
+.SH SEE ALSO
+.BR tc (8)