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Subject[PATCH] docs: bpf: Added more extension example
Date
From: "Roy, UjjaL" <royujjal@gmail.com>

After reading this document observed that for new users it is
hard to find an example of "extension" easily.

So, added a new heading for extensions for better readability.
Now, the new readers can easily identify "extension" examples.
Also, added one more example of filtering interface index.

Signed-off-by: Roy, UjjaL <royujjal@gmail.com>
---
Documentation/networking/filter.rst | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 3e2221f4abe4..5f13905b12e0 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -320,13 +320,6 @@ Examples for low-level BPF:
ret #-1
drop: ret #0

-**(Accelerated) VLAN w/ id 10**::
-
- ld vlan_tci
- jneq #10, drop
- ret #-1
- drop: ret #0
-
**icmp random packet sampling, 1 in 4**::

ldh [12]
@@ -358,6 +351,22 @@ Examples for low-level BPF:
bad: ret #0 /* SECCOMP_RET_KILL_THREAD */
good: ret #0x7fff0000 /* SECCOMP_RET_ALLOW */

+Examples for low-level BPF extension:
+
+**Packet for interface index 13**::
+
+ ld ifidx
+ jneq #13, drop
+ ret #-1
+ drop: ret #0
+
+**(Accelerated) VLAN w/ id 10**::
+
+ ld vlan_tci
+ jneq #10, drop
+ ret #-1
+ drop: ret #0
+
The above example code can be placed into a file (here called "foo"), and
then be passed to the bpf_asm tool for generating opcodes, output that xt_bpf
and cls_bpf understands and can directly be loaded with. Example with above
--
2.17.1
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