Documentation: add a guideline for hard_start_xmit method
Add a guideline not to modify SKBs.
Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/Documentation/networking/driver.txt b/Documentation/networking/driver.txt
index 4f7da5a..ea72d2e 100644
--- a/Documentation/networking/driver.txt
+++ b/Documentation/networking/driver.txt
@@ -61,7 +61,10 @@
2) Do not forget to update netdev->trans_start to jiffies after
each new tx packet is given to the hardware.
-3) Do not forget that once you return 0 from your hard_start_xmit
+3) A hard_start_xmit method must not modify the shared parts of a
+ cloned SKB.
+
+4) Do not forget that once you return 0 from your hard_start_xmit
method, it is your driver's responsibility to free up the SKB
and in some finite amount of time.