{"id":2843,"date":"2022-12-20T15:17:28","date_gmt":"2022-12-20T18:17:28","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/simple-action-in-tc-man8\/"},"modified":"2022-12-20T15:17:28","modified_gmt":"2022-12-20T18:17:28","slug":"simple-action-in-tc-man8","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/simple-action-in-tc-man8\/","title":{"rendered":"Simple action in tc (man8)"},"content":{"rendered":"

Simple action in tc<\/h1>\n

NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
OPTIONS<\/a>
EXAMPLES<\/a>
SEE ALSO<\/a> <\/p>\n

\n

NAME <\/a> <\/h2>\n

simple – basic example action<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

tc<\/b> … action simple<\/b> [ sdata<\/b> STRING<\/i> ] [ index<\/b> INDEX<\/i> ] [ CONTROL<\/i> ]<\/p>\n

CONTROL<\/i> := { reclassify<\/b> | pipe<\/b> | drop<\/b> | continue<\/b> | ok<\/b> }<\/p>\n

DESCRIPTION <\/a> <\/h2>\n

This is a pedagogical example rather than an actually useful action. Upon every access, it prints the given STRING<\/i> which may be of arbitrary length.<\/p>\n

OPTIONS <\/a> <\/h2>\n

sdata<\/b> STRING<\/i><\/p>\n

The actual string to print.<\/p>\n

index<\/b> INDEX<\/i><\/p>\n

Optional action index value.<\/p>\n

CONTROL<\/i><\/p>\n

Indicate how tc<\/b> should proceed after executing the action. For a description of the possible CONTROL<\/i> values, see tc-actions<\/b>(8).<\/p>\n

EXAMPLES <\/a> <\/h2>\n

The following example makes the kernel yell “Incoming ICMP!” every time it sees an incoming ICMP on eth0. Steps are:<\/p>\n\n\n\n\n\n\n\n
<\/td>\n\n

1)<\/p>\n<\/td>\n

<\/td>\n\n

Add an ingress qdisc point to eth0<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

2)<\/p>\n<\/td>\n

<\/td>\n\n

Start a chain on ingress of eth0 that first matches ICMP then invokes the simple action to shout.<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

3)<\/p>\n<\/td>\n

<\/td>\n\n

display stats and show that no packet has been seen by the action<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

4)<\/p>\n<\/td>\n

<\/td>\n\n

Send one ping packet to google (expect to receive a response back)<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

5)<\/p>\n<\/td>\n

<\/td>\n\n

grep the logs to see the logged message<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

6)<\/p>\n<\/td>\n

<\/td>\n\n

display stats again and observe increment by 1<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

hadi@noma1:$ tc qdisc add dev eth0 ingress
hadi@noma1:$tc filter add dev eth0 parent ffff: protocol ip prio 5 <\/p>\n\n\n
<\/td>\n\n

u32 match ip protocol 1 0xff flowid 1:1 action simple sdata “Incoming ICMP”<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

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<\/p>\n\n\n\n\n\n\n\n\n
<\/td>\n<\/td>\n<\/td>\n\n

action order 1: Simple <\/p>\n<\/td>\n<\/tr>\n

<\/td>\n<\/td>\n<\/td>\n\n

index 4 ref 1 bind 1 installed 29 sec used 29 sec<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n<\/td>\n<\/td>\n\n

Action statistics:<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n<\/td>\n <\/td>\n <\/td>\n<\/tr>\n
<\/td>\n<\/td>\n<\/td>\n\n

Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n<\/td>\n <\/td>\n <\/td>\n<\/tr>\n
<\/td>\n<\/td>\n<\/td>\n\n

backlog 0b 0p requeues 0<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

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<\/p>\n

— 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<\/p>\n

hadi@noma1$ dmesg | grep simple
[135354.473951] simple: Incoming ICMP_1<\/p>\n

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<\/p>\n\n\n\n\n\n\n
<\/td>\n\n

action order 1: Simple <\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

index 4 ref 1 bind 1 installed 206 sec used 67 sec<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

Action statistics:<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

Sent 84 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)<\/p>\n<\/td>\n<\/tr>\n

<\/td>\n\n

backlog 0b 0p requeues 0<\/p>\n<\/td>\n<\/tr>\n<\/table>\n

SEE ALSO <\/a> <\/h2>\n

tc<\/b>(8) tc-actions<\/b>(8)<\/p>\n

\n","protected":false},"excerpt":{"rendered":"

simple – basic example action <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[5,52,4,193],"class_list":["post-2843","post","type-post","status-publish","format-standard","hentry","category-8-administracion-del-sistema","tag-5","tag-administracion","tag-man8","tag-tc-simple"],"gutentor_comment":0,"_links":{"self":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/2843","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/comments?post=2843"}],"version-history":[{"count":0,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/2843\/revisions"}],"wp:attachment":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/media?parent=2843"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/categories?post=2843"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/tags?post=2843"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}