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