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Date: Wed, 7 Jul 2021 23:10:22 +0530
From: UjjaL Roy <royujjal@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Jonathan Corbet <corbet@....net>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, clang-built-linux@...glegroups.com
Subject: [PATCH] docs: bpf: Added more extension example
From: "Roy, UjjaL" <royujjal@...il.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@...il.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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