d892afe2ca
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>
29 lines
1.2 KiB
Text
29 lines
1.2 KiB
Text
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The "enviromental" rules for authors of any new tc actions are:
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1) If you stealeth or borroweth any packet thou shalt be branching
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from the righteous path and thou shalt cloneth.
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For example if your action queues a packet to be processed later
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or intentionaly branches by redirecting a packet then you need to
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clone the packet.
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There are certain fields in the skb tc_verd that need to be reset so we
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avoid loops etc. A few are generic enough so much so that skb_act_clone()
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resets them for you. So invoke skb_act_clone() rather than skb_clone()
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2) If you munge any packet thou shalt call pskb_expand_head in the case
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someone else is referencing the skb. After that you "own" the skb.
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You must also tell us if it is ok to munge the packet (TC_OK2MUNGE),
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this way any action downstream can stomp on the packet.
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3) dropping packets you dont own is a nono. You simply return
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TC_ACT_SHOT to the caller and they will drop it.
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The "enviromental" rules for callers of actions (qdiscs etc) are:
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*) thou art responsible for freeing anything returned as being
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TC_ACT_SHOT/STOLEN/QUEUED. If none of TC_ACT_SHOT/STOLEN/QUEUED is
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returned then all is great and you dont need to do anything.
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Post on netdev if something is unclear.
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