path: root/Documentation/networking/tc-actions-env-rules.txt
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+The "environmental" 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 intentionally 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 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 don't own is a no-no. You simply return
+TC_ACT_SHOT to the caller and they will drop it.
+The "environmental" rules for callers of actions (qdiscs etc) are:
+*) Thou art responsible for freeing anything returned as being
+returned, then all is great and you don't need to do anything.
+Post on netdev if something is unclear.