1
2#include <stdint.h>
3#include <stdbool.h>
4#include <stddef.h>
5
6#include <linux/bpf.h>
7#include <linux/stddef.h>
8#include <linux/pkt_cls.h>
9#include <linux/if_ether.h>
10#include <linux/in.h>
11#include <linux/ip.h>
12#include <linux/ipv6.h>
13
14#include <bpf/bpf_helpers.h>
15#include <bpf/bpf_endian.h>
16
17#ifndef ctx_ptr
18# define ctx_ptr(field) (void *)(long)(field)
19#endif
20
21#define AF_INET 2
22#define AF_INET6 10
23
24static __always_inline int fill_fib_params_v4(struct __sk_buff *skb,
25 struct bpf_fib_lookup *fib_params)
26{
27 void *data_end = ctx_ptr(skb->data_end);
28 void *data = ctx_ptr(skb->data);
29 struct iphdr *ip4h;
30
31 if (data + sizeof(struct ethhdr) > data_end)
32 return -1;
33
34 ip4h = (struct iphdr *)(data + sizeof(struct ethhdr));
35 if ((void *)(ip4h + 1) > data_end)
36 return -1;
37
38 fib_params->family = AF_INET;
39 fib_params->tos = ip4h->tos;
40 fib_params->l4_protocol = ip4h->protocol;
41 fib_params->sport = 0;
42 fib_params->dport = 0;
43 fib_params->tot_len = bpf_ntohs(ip4h->tot_len);
44 fib_params->ipv4_src = ip4h->saddr;
45 fib_params->ipv4_dst = ip4h->daddr;
46
47 return 0;
48}
49
50static __always_inline int fill_fib_params_v6(struct __sk_buff *skb,
51 struct bpf_fib_lookup *fib_params)
52{
53 struct in6_addr *src = (struct in6_addr *)fib_params->ipv6_src;
54 struct in6_addr *dst = (struct in6_addr *)fib_params->ipv6_dst;
55 void *data_end = ctx_ptr(skb->data_end);
56 void *data = ctx_ptr(skb->data);
57 struct ipv6hdr *ip6h;
58
59 if (data + sizeof(struct ethhdr) > data_end)
60 return -1;
61
62 ip6h = (struct ipv6hdr *)(data + sizeof(struct ethhdr));
63 if ((void *)(ip6h + 1) > data_end)
64 return -1;
65
66 fib_params->family = AF_INET6;
67 fib_params->flowinfo = 0;
68 fib_params->l4_protocol = ip6h->nexthdr;
69 fib_params->sport = 0;
70 fib_params->dport = 0;
71 fib_params->tot_len = bpf_ntohs(ip6h->payload_len);
72 *src = ip6h->saddr;
73 *dst = ip6h->daddr;
74
75 return 0;
76}
77
78SEC("chk_egress") int tc_chk(struct __sk_buff *skb)
79{
80 void *data_end = ctx_ptr(skb->data_end);
81 void *data = ctx_ptr(skb->data);
82 __u32 *raw = data;
83
84 if (data + sizeof(struct ethhdr) > data_end)
85 return TC_ACT_SHOT;
86
87 return !raw[0] && !raw[1] && !raw[2] ? TC_ACT_SHOT : TC_ACT_OK;
88}
89
90static __always_inline int tc_redir(struct __sk_buff *skb)
91{
92 struct bpf_fib_lookup fib_params = { .ifindex = skb->ingress_ifindex };
93 __u8 zero[ETH_ALEN * 2];
94 int ret = -1;
95
96 switch (skb->protocol) {
97 case __bpf_constant_htons(ETH_P_IP):
98 ret = fill_fib_params_v4(skb, &fib_params);
99 break;
100 case __bpf_constant_htons(ETH_P_IPV6):
101 ret = fill_fib_params_v6(skb, &fib_params);
102 break;
103 }
104
105 if (ret)
106 return TC_ACT_OK;
107
108 ret = bpf_fib_lookup(skb, &fib_params, sizeof(fib_params), 0);
109 if (ret == BPF_FIB_LKUP_RET_NOT_FWDED || ret < 0)
110 return TC_ACT_OK;
111
112 __builtin_memset(&zero, 0, sizeof(zero));
113 if (bpf_skb_store_bytes(skb, 0, &zero, sizeof(zero), 0) < 0)
114 return TC_ACT_SHOT;
115
116 if (ret == BPF_FIB_LKUP_RET_NO_NEIGH) {
117 struct bpf_redir_neigh nh_params = {};
118
119 nh_params.nh_family = fib_params.family;
120 __builtin_memcpy(&nh_params.ipv6_nh, &fib_params.ipv6_dst,
121 sizeof(nh_params.ipv6_nh));
122
123 return bpf_redirect_neigh(fib_params.ifindex, &nh_params,
124 sizeof(nh_params), 0);
125
126 } else if (ret == BPF_FIB_LKUP_RET_SUCCESS) {
127 void *data_end = ctx_ptr(skb->data_end);
128 struct ethhdr *eth = ctx_ptr(skb->data);
129
130 if (eth + 1 > data_end)
131 return TC_ACT_SHOT;
132
133 __builtin_memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);
134 __builtin_memcpy(eth->h_source, fib_params.smac, ETH_ALEN);
135
136 return bpf_redirect(fib_params.ifindex, 0);
137 }
138
139 return TC_ACT_SHOT;
140}
141
142
143
144
145SEC("dst_ingress") int tc_dst(struct __sk_buff *skb)
146{
147 return tc_redir(skb);
148}
149
150SEC("src_ingress") int tc_src(struct __sk_buff *skb)
151{
152 return tc_redir(skb);
153}
154
155char __license[] SEC("license") = "GPL";
156
