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author | 2007-10-26 02:49:09 -0700 | |
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committer | 2007-10-26 02:49:09 -0700 | |
commit | d892afe2ca905ddb00a4f16927c8b465cdd31b20 (patch) | |
tree | c15295f448a19046423bbb480fcfefe319f91928 | |
parent | [NET_CLS_ACT]: Use skb_act_clone (diff) | |
download | linux-d892afe2ca905ddb00a4f16927c8b465cdd31b20.tar.gz linux-d892afe2ca905ddb00a4f16927c8b465cdd31b20.tar.bz2 linux-d892afe2ca905ddb00a4f16927c8b465cdd31b20.zip |
[NET]: Document some simple rules for actions
This patch adds documentation on what is expected of an
action which branches away from the action-graph or when it
needs to trample on actins. It also describes what is expected of
users of such actions.
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | Documentation/networking/tc-actions-env-rules.txt | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/networking/tc-actions-env-rules.txt b/Documentation/networking/tc-actions-env-rules.txt new file mode 100644 index 000000000000..01e716d185f4 --- /dev/null +++ b/Documentation/networking/tc-actions-env-rules.txt @@ -0,0 +1,29 @@ + +The "enviromental" rules for authors of any new tc actions are: + +1) If you stealeth or borroweth any packet thou shalt be branching +from the righteous path and thou shalt cloneth. + +For example if your action queues a packet to be processed later +or intentionaly branches by redirecting a packet then you need to +clone the packet. +There are certain fields in the skb tc_verd that need to be reset so we +avoid loops etc. A few are generic enough so much so that skb_act_clone() +resets them for you. So invoke skb_act_clone() rather than skb_clone() + +2) If you munge any packet thou shalt call pskb_expand_head in the case +someone else is referencing the skb. After that you "own" the skb. +You must also tell us if it is ok to munge the packet (TC_OK2MUNGE), +this way any action downstream can stomp on the packet. + +3) dropping packets you dont own is a nono. You simply return +TC_ACT_SHOT to the caller and they will drop it. + +The "enviromental" rules for callers of actions (qdiscs etc) are: + +*) thou art responsible for freeing anything returned as being +TC_ACT_SHOT/STOLEN/QUEUED. If none of TC_ACT_SHOT/STOLEN/QUEUED is +returned then all is great and you dont need to do anything. + +Post on netdev if something is unclear. + |