Commit 88865347 authored by Roy, UjjaL's avatar Roy, UjjaL Committed by Daniel Borkmann
Browse files

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: default avatarRoy, UjjaL <royujjal@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/CAADnVQJ=DoRDcVkaXmY3EmNdLoO7gq1mkJOn5G=00wKH8qUtZQ@mail.gmail.com
parent c7603cfa

Documentation/networking/filter.rst

+16 −7
Original line number Diff line number Diff line
@@ -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