TC Actions - Environmental RulesÂķ

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.

  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.

  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:

  1. 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 don’t need to do anything.

Post on netdev if something is unclear.