From 8886534747c2e56d9d3b978c99e92dc479cd9426 Mon Sep 17 00:00:00 2001 From: "Roy, UjjaL" Date: Fri, 16 Jul 2021 22:04:41 +0200 Subject: 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 Signed-off-by: Daniel Borkmann Acked-by: Song Liu Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/CAADnVQJ=DoRDcVkaXmY3EmNdLoO7gq1mkJOn5G=00wKH8qUtZQ@mail.gmail.com --- Documentation/networking/filter.rst | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) (limited to 'Documentation') 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 -- cgit v1.2.3