| Mauro Carvalho Chehab | d2461ed | 2020-04-30 18:04:28 +0200 | [diff] [blame] | 1 | .. SPDX-License-Identifier: GPL-2.0 |
| 2 | |
| 3 | ================================ |
| 4 | TC Actions - Environmental Rules |
| 5 | ================================ |
| 6 | |
| 7 | |
| 8 | The "environmental" rules for authors of any new tc actions are: |
| 9 | |
| 10 | 1) If you stealeth or borroweth any packet thou shalt be branching |
| 11 | from the righteous path and thou shalt cloneth. |
| 12 | |
| 13 | For example if your action queues a packet to be processed later, |
| 14 | or intentionally branches by redirecting a packet, then you need to |
| 15 | clone the packet. |
| 16 | |
| 17 | 2) If you munge any packet thou shalt call pskb_expand_head in the case |
| 18 | someone else is referencing the skb. After that you "own" the skb. |
| 19 | |
| 20 | 3) Dropping packets you don't own is a no-no. You simply return |
| 21 | TC_ACT_SHOT to the caller and they will drop it. |
| 22 | |
| 23 | The "environmental" rules for callers of actions (qdiscs etc) are: |
| 24 | |
| 25 | #) Thou art responsible for freeing anything returned as being |
| 26 | TC_ACT_SHOT/STOLEN/QUEUED. If none of TC_ACT_SHOT/STOLEN/QUEUED is |
| 27 | returned, then all is great and you don't need to do anything. |
| 28 | |
| 29 | Post on netdev if something is unclear. |