cheers, jamal
[NET_DOC] 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 <[EMAIL PROTECTED]> --- 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 0000000..c684f48 --- /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 skb_expand 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. + -- 1.4.4.1.gaed4
