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authorRoy, UjjaL <royujjal@gmail.com>2021-07-16 23:04:41 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2021-07-16 23:08:17 +0300
commit8886534747c2e56d9d3b978c99e92dc479cd9426 (patch)
tree1468de456a9d96735b4a5a2b26cb6c8f9075e53b /Documentation/networking
parentc7603cfa04e7c3a435b31d065f7cbdc829428f6e (diff)
downloadlinux-8886534747c2e56d9d3b978c99e92dc479cd9426.tar.xz
bpf, doc: Add heading and example for extensions in cbpf
Add new heading for extensions to make it more readable. Also, add one more example of filtering interface index for better understanding. Signed-off-by: Roy, UjjaL <royujjal@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Song Liu <songliubraving@fb.com> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/CAADnVQJ=DoRDcVkaXmY3EmNdLoO7gq1mkJOn5G=00wKH8qUtZQ@mail.gmail.com
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/filter.rst23
1 files 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