NAME

       simple - basic example action

SYNOPSIS

       tc ... action simple [ sdata STRING ] [ index INDEX ] [ CONTROL ]

       CONTROL := { reclassify | pipe | drop | continue | ok }

DESCRIPTION

       This is a pedagogical example rather than an actually useful action. Upon every access, it
       prints the given STRING which may be of arbitrary length.

OPTIONS

       sdata STRING
              The actual string to print.

       index INDEX
              Optional action index value.

       CONTROL
              Indicate how tc should proceed after executing the action. For a description of the
              possible CONTROL values, see tc-actions(8).

EXAMPLES

       The  following  example  makes  the  kernel  yell  "Incoming  ICMP!" every time it sees an
       incoming ICMP on eth0. Steps are:

       1)  Add an ingress qdisc point to eth0

       2)  Start a chain on ingress of eth0 that first  matches  ICMP  then  invokes  the  simple
           action to shout.

       3)  display stats and show that no packet has been seen by the action

       4)  Send one ping packet to google (expect to receive a response back)

       5)  grep the logs to see the logged message

       6)  display stats again and observe increment by 1

             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 <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

SEE ALSO

       tc(8) tc-actions(8)