From: Alexei Starovoitov <ast@plumgrid.com>
Date: Mon, 1 Dec 2014 23:06:36 +0000 (-0800)
Subject: samples: bpf: example of stateful socket filtering
X-Git-Tag: omap-for-v3.20/drop-legacy-3517~122^2~93^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=03f4723ed7a52bd31da26eefe2cdde563ea0f468;p=pandora-kernel.git

samples: bpf: example of stateful socket filtering

this socket filter example does:
- creates arraymap in kernel with key 4 bytes and value 8 bytes

- loads eBPF program which assumes that packet is IPv4 and loads one byte of
  IP->proto from the packet and uses it as a key in a map

  r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
  *(u32*)(fp - 4) = r0;
  value = bpf_map_lookup_elem(map_fd, fp - 4);
  if (value)
       (*(u64*)value) += 1;

- attaches this program to raw socket

- every second user space reads map[IPPROTO_TCP], map[IPPROTO_UDP], map[IPPROTO_ICMP]
  to see how many packets of given protocol were seen on loopback interface

Usage:
$sudo samples/bpf/sock_example
TCP 0 UDP 0 ICMP 0 packets
TCP 187600 UDP 0 ICMP 4 packets
TCP 376504 UDP 0 ICMP 8 packets
TCP 563116 UDP 0 ICMP 12 packets
TCP 753144 UDP 0 ICMP 16 packets

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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