1 // SPDX-License-Identifier: GPL-2.0
2 #include <vmlinux.h>
3 #include <bpf/bpf_helpers.h>
4 
5 #define ETH_ALEN 6
6 #define HDR_SZ (sizeof(struct ethhdr) + sizeof(struct ipv6hdr) + sizeof(struct udphdr))
7 const volatile int ifindex_out;
8 const volatile int ifindex_in;
9 const volatile __u8 expect_dst[ETH_ALEN];
10 volatile int pkts_seen_xdp = 0;
11 volatile int pkts_seen_zero = 0;
12 volatile int pkts_seen_tc = 0;
13 volatile int retcode = XDP_REDIRECT;
14 
15 SEC("xdp")
16 int xdp_redirect(struct xdp_md *xdp)
17 {
18 	__u32 *metadata = (void *)(long)xdp->data_meta;
19 	void *data_end = (void *)(long)xdp->data_end;
20 	void *data = (void *)(long)xdp->data;
21 
22 	__u8 *payload = data + HDR_SZ;
23 	int ret = retcode;
24 
25 	if (payload + 1 > data_end)
26 		return XDP_ABORTED;
27 
28 	if (xdp->ingress_ifindex != ifindex_in)
29 		return XDP_ABORTED;
30 
31 	if (metadata + 1 > data)
32 		return XDP_ABORTED;
33 
34 	if (*metadata != 0x42)
35 		return XDP_ABORTED;
36 
37 	if (*payload == 0) {
38 		*payload = 0x42;
39 		pkts_seen_zero++;
40 	}
41 
42 	if (bpf_xdp_adjust_meta(xdp, 4))
43 		return XDP_ABORTED;
44 
45 	if (retcode > XDP_PASS)
46 		retcode--;
47 
48 	if (ret == XDP_REDIRECT)
49 		return bpf_redirect(ifindex_out, 0);
50 
51 	return ret;
52 }
53 
54 static bool check_pkt(void *data, void *data_end)
55 {
56 	struct ipv6hdr *iph = data + sizeof(struct ethhdr);
57 	__u8 *payload = data + HDR_SZ;
58 
59 	if (payload + 1 > data_end)
60 		return false;
61 
62 	if (iph->nexthdr != IPPROTO_UDP || *payload != 0x42)
63 		return false;
64 
65 	/* reset the payload so the same packet doesn't get counted twice when
66 	 * it cycles back through the kernel path and out the dst veth
67 	 */
68 	*payload = 0;
69 	return true;
70 }
71 
72 SEC("xdp")
73 int xdp_count_pkts(struct xdp_md *xdp)
74 {
75 	void *data = (void *)(long)xdp->data;
76 	void *data_end = (void *)(long)xdp->data_end;
77 
78 	if (check_pkt(data, data_end))
79 		pkts_seen_xdp++;
80 
81 	/* Return XDP_DROP to make sure the data page is recycled, like when it
82 	 * exits a physical NIC. Recycled pages will be counted in the
83 	 * pkts_seen_zero counter above.
84 	 */
85 	return XDP_DROP;
86 }
87 
88 SEC("tc")
89 int tc_count_pkts(struct __sk_buff *skb)
90 {
91 	void *data = (void *)(long)skb->data;
92 	void *data_end = (void *)(long)skb->data_end;
93 
94 	if (check_pkt(data, data_end))
95 		pkts_seen_tc++;
96 
97 	return 0;
98 }
99 
100 char _license[] SEC("license") = "GPL";
101