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a80857822b
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>
26 lines
553 B
C
26 lines
553 B
C
#include <uapi/linux/bpf.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/ip.h>
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#include "bpf_helpers.h"
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struct bpf_map_def SEC("maps") my_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(u32),
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.value_size = sizeof(long),
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.max_entries = 256,
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};
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SEC("socket1")
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int bpf_prog1(struct sk_buff *skb)
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{
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int index = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
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long *value;
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value = bpf_map_lookup_elem(&my_map, &index);
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if (value)
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__sync_fetch_and_add(value, 1);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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