1 // SPDX-License-Identifier: GPL-2.0
2 #include <stddef.h>
3 #include <string.h>
4 #include <linux/bpf.h>
5 #include <linux/ip.h>
6 #include <linux/ipv6.h>
7 #include <bpf/bpf_helpers.h>
8 #include <bpf/bpf_endian.h>
9
10 struct grehdr {
11 __be16 flags;
12 __be16 protocol;
13 };
14
15 SEC("encap_gre")
16 int bpf_lwt_encap_gre(struct __sk_buff *skb)
17 {
18 struct encap_hdr {
19 struct iphdr iph;
20 struct grehdr greh;
21 } hdr;
22 int err;
23
24 memset(&hdr, 0, sizeof(struct encap_hdr));
25
26 hdr.iph.ihl = 5;
27 hdr.iph.version = 4;
28 hdr.iph.ttl = 0x40;
29 hdr.iph.protocol = 47; /* IPPROTO_GRE */
30 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
31 hdr.iph.saddr = 0x640110ac; /* 172.16.1.100 */
32 hdr.iph.daddr = 0x641010ac; /* 172.16.16.100 */
33 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
34 hdr.iph.saddr = 0xac100164; /* 172.16.1.100 */
35 hdr.iph.daddr = 0xac101064; /* 172.16.16.100 */
36 #else
37 #error "Fix your compiler's __BYTE_ORDER__?!"
38 #endif
39 hdr.iph.tot_len = bpf_htons(skb->len + sizeof(struct encap_hdr));
40
41 hdr.greh.protocol = skb->protocol;
42
43 err = bpf_lwt_push_encap(skb, BPF_LWT_ENCAP_IP, &hdr,
44 sizeof(struct encap_hdr));
45 if (err)
46 return BPF_DROP;
47
48 return BPF_LWT_REROUTE;
49 }
50
51 SEC("encap_gre6")
52 int bpf_lwt_encap_gre6(struct __sk_buff *skb)
53 {
54 struct encap_hdr {
55 struct ipv6hdr ip6hdr;
56 struct grehdr greh;
57 } hdr;
58 int err;
59
60 memset(&hdr, 0, sizeof(struct encap_hdr));
61
62 hdr.ip6hdr.version = 6;
63 hdr.ip6hdr.payload_len = bpf_htons(skb->len + sizeof(struct grehdr));
64 hdr.ip6hdr.nexthdr = 47; /* IPPROTO_GRE */
65 hdr.ip6hdr.hop_limit = 0x40;
66 /* fb01::1 */
67 hdr.ip6hdr.saddr.s6_addr[0] = 0xfb;
68 hdr.ip6hdr.saddr.s6_addr[1] = 1;
69 hdr.ip6hdr.saddr.s6_addr[15] = 1;
70 /* fb10::1 */
71 hdr.ip6hdr.daddr.s6_addr[0] = 0xfb;
72 hdr.ip6hdr.daddr.s6_addr[1] = 0x10;
73 hdr.ip6hdr.daddr.s6_addr[15] = 1;
74
75 hdr.greh.protocol = skb->protocol;
76
77 err = bpf_lwt_push_encap(skb, BPF_LWT_ENCAP_IP, &hdr,
78 sizeof(struct encap_hdr));
79 if (err)
80 return BPF_DROP;
81
82 return BPF_LWT_REROUTE;
83 }
84
85 char _license[] SEC("license") = "GPL";
86
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