1 #include <linux/bpf.h>
2 #include <linux/if_ether.h>
3 #include <linux/pkt_cls.h>
4
5 #include <bpf/bpf_helpers.h>
6
7 #define META_SIZE 32
8
9 #define ctx_ptr(ctx, mem) (void *)(unsigned long)ctx->mem
10
11 /* Demonstrates how metadata can be passed from an XDP program to a TC program
12 * using bpf_xdp_adjust_meta.
13 * For the sake of testing the metadata support in drivers, the XDP program uses
14 * a fixed-size payload after the Ethernet header as metadata. The TC program
15 * copies the metadata it receives into a map so it can be checked from
16 * userspace.
17 */
18
19 struct {
20 __uint(type, BPF_MAP_TYPE_ARRAY);
21 __uint(max_entries, 1);
22 __type(key, __u32);
23 __uint(value_size, META_SIZE);
24 } test_result SEC(".maps");
25
26 SEC("tc")
ing_cls(struct __sk_buff * ctx)27 int ing_cls(struct __sk_buff *ctx)
28 {
29 __u8 *data, *data_meta;
30 __u32 key = 0;
31
32 data_meta = ctx_ptr(ctx, data_meta);
33 data = ctx_ptr(ctx, data);
34
35 if (data_meta + META_SIZE > data)
36 return TC_ACT_SHOT;
37
38 bpf_map_update_elem(&test_result, &key, data_meta, BPF_ANY);
39
40 return TC_ACT_SHOT;
41 }
42
43 SEC("xdp")
ing_xdp(struct xdp_md * ctx)44 int ing_xdp(struct xdp_md *ctx)
45 {
46 __u8 *data, *data_meta, *data_end, *payload;
47 struct ethhdr *eth;
48 int ret;
49
50 ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
51 if (ret < 0)
52 return XDP_DROP;
53
54 data_meta = ctx_ptr(ctx, data_meta);
55 data_end = ctx_ptr(ctx, data_end);
56 data = ctx_ptr(ctx, data);
57
58 eth = (struct ethhdr *)data;
59 payload = data + sizeof(struct ethhdr);
60
61 if (payload + META_SIZE > data_end ||
62 data_meta + META_SIZE > data)
63 return XDP_DROP;
64
65 /* The Linux networking stack may send other packets on the test
66 * interface that interfere with the test. Just drop them.
67 * The test packets can be recognized by their ethertype of zero.
68 */
69 if (eth->h_proto != 0)
70 return XDP_DROP;
71
72 __builtin_memcpy(data_meta, payload, META_SIZE);
73 return XDP_PASS;
74 }
75
76 char _license[] SEC("license") = "GPL";
77