
The "enviromental" 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 intentionaly 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 so much so 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 dont own is a nono. You simply return
TC_ACT_SHOT to the caller and they will drop it.

The "enviromental" rules for callers of actions (qdiscs etc) are:

*) 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 dont need to do anything.

Post on netdev if something is unclear.


Document some simple rules for actions
[NET]: Document some simple rules for actions

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 <f626bfe8a6716f0e60b0f3989b67f5ad2fa9fda2@cyberus.ca>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>
