tc-actions-env-rules.rst 1.0 KB

1234567891011121314151617181920212223242526272829
  1. .. SPDX-License-Identifier: GPL-2.0
  2. ================================
  3. TC Actions - Environmental Rules
  4. ================================
  5. The "environmental" rules for authors of any new tc actions are:
  6. 1) If you stealeth or borroweth any packet thou shalt be branching
  7. from the righteous path and thou shalt cloneth.
  8. For example if your action queues a packet to be processed later,
  9. or intentionally branches by redirecting a packet, then you need to
  10. clone the packet.
  11. 2) If you munge any packet thou shalt call pskb_expand_head in the case
  12. someone else is referencing the skb. After that you "own" the skb.
  13. 3) Dropping packets you don't own is a no-no. You simply return
  14. TC_ACT_SHOT to the caller and they will drop it.
  15. The "environmental" rules for callers of actions (qdiscs etc) are:
  16. #) Thou art responsible for freeing anything returned as being
  17. TC_ACT_SHOT/STOLEN/QUEUED. If none of TC_ACT_SHOT/STOLEN/QUEUED is
  18. returned, then all is great and you don't need to do anything.
  19. Post on netdev if something is unclear.