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>
diff --git a/samples/bpf/libbpf.c b/samples/bpf/libbpf.c
index 17bb520..46d50b7 100644
--- a/samples/bpf/libbpf.c
+++ b/samples/bpf/libbpf.c
@@ -7,6 +7,10 @@
#include <linux/netlink.h>
#include <linux/bpf.h>
#include <errno.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <linux/if_packet.h>
+#include <arpa/inet.h>
#include "libbpf.h"
static __u64 ptr_to_u64(void *ptr)
@@ -93,3 +97,27 @@
return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
}
+
+int open_raw_sock(const char *name)
+{
+ struct sockaddr_ll sll;
+ int sock;
+
+ sock = socket(PF_PACKET, SOCK_RAW | SOCK_NONBLOCK | SOCK_CLOEXEC, htons(ETH_P_ALL));
+ if (sock < 0) {
+ printf("cannot create raw socket\n");
+ return -1;
+ }
+
+ memset(&sll, 0, sizeof(sll));
+ sll.sll_family = AF_PACKET;
+ sll.sll_ifindex = if_nametoindex(name);
+ sll.sll_protocol = htons(ETH_P_ALL);
+ if (bind(sock, (struct sockaddr *)&sll, sizeof(sll)) < 0) {
+ printf("bind to %s: %s\n", name, strerror(errno));
+ close(sock);
+ return -1;
+ }
+
+ return sock;
+}