samples: bpf: trivial eBPF program in C
this example does the same task as previous socket example
in assembler, but this one does it in C.
eBPF program in kernel does:
/* assume that packet is IPv4, load one byte of IP->proto */
int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
long *value;
value = bpf_map_lookup_elem(&my_map, &index);
if (value)
__sync_fetch_and_add(value, 1);
Corresponding user space reads map[tcp], map[udp], map[icmp]
and prints protocol stats every second
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/samples/bpf/sockex1_kern.c b/samples/bpf/sockex1_kern.c
new file mode 100644
index 0000000..0668926
--- /dev/null
+++ b/samples/bpf/sockex1_kern.c
@@ -0,0 +1,25 @@
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/ip.h>
+#include "bpf_helpers.h"
+
+struct bpf_map_def SEC("maps") my_map = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(u32),
+ .value_size = sizeof(long),
+ .max_entries = 256,
+};
+
+SEC("socket1")
+int bpf_prog1(struct sk_buff *skb)
+{
+ int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
+ long *value;
+
+ value = bpf_map_lookup_elem(&my_map, &index);
+ if (value)
+ __sync_fetch_and_add(value, 1);
+
+ return 0;
+}
+char _license[] SEC("license") = "GPL";