linux-stable/Documentation/networking/tc-actions-env-rules.rst
Mauro Carvalho Chehab d2461edde7 docs: networking: convert tc-actions-env-rules.txt to ReST
- add SPDX header;
- add a document title;
- use the right numbered list markup;
- adjust identation, whitespaces and blank lines where needed;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-04-30 12:56:38 -07:00

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.. SPDX-License-Identifier: GPL-2.0
================================
TC Actions - Environmental Rules
================================
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:
#) 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.