.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" [ .BI sdata " STRING" ] [ .BI index " INDEX" ] [ .I CONTROL ] .ti -8 .IR CONTROL " := {" .BR reclassify " | " pipe " | " drop " | " continue " | " ok " }" .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 .BI sdata " STRING" The actual string to print. .TP .BI index " INDEX" Optional action index value. .TP .I CONTROL Indicate how .B tc should proceed after executing the action. For a description of the possible .I CONTROL values, see .BR tc-actions (8). .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:$tc filter add dev eth0 parent ffff: protocol ip prio 5 \\ u32 match ip protocol 1 0xff flowid 1:1 action simple sdata "Incoming ICMP" hadi@noma1:$ 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 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 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) .BR tc-actions (8)