Simple action in tc(8)    (12 Jan 2015)    Simple action in tc(8)

     NAME
          simple - basic example action

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

          CONTROL := { reclassify | pipe | drop |

     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 val-
               ues, 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"

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     Simple action in tc(8)    (12 Jan 2015)    Simple action in tc(8)

                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)

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