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From:   UjjaL Roy <royujjal@gmail.com>
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, clang-built-linux@googlegroups.com
Subject: [PATCH] docs: bpf: Added more extension example
Date:   Wed,  7 Jul 2021 23:10:22 +0530
Message-Id: <20210707174022.517-1-royujjal@gmail.com>
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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