1 /* Copyright (c) 2016 Facebook
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program shows how to use bpf_xdp_adjust_head() by
8 * encapsulating the incoming packet in an IPv4/v6 header
9 * and then XDP_TX it out.
10 */
11 #define KBUILD_MODNAME "foo"
12 #include <uapi/linux/bpf.h>
13 #include <linux/in.h>
14 #include <linux/if_ether.h>
15 #include <linux/if_packet.h>
16 #include <linux/if_vlan.h>
17 #include <linux/ip.h>
18 #include <linux/ipv6.h>
19 #include <bpf/bpf_helpers.h>
20 #include "xdp_tx_iptunnel_common.h"
21
22 struct {
23 __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
24 __type(key, __u32);
25 __type(value, __u64);
26 __uint(max_entries, 256);
27 } rxcnt SEC(".maps");
28
29 struct {
30 __uint(type, BPF_MAP_TYPE_HASH);
31 __type(key, struct vip);
32 __type(value, struct iptnl_info);
33 __uint(max_entries, MAX_IPTNL_ENTRIES);
34 } vip2tnl SEC(".maps");
35
36 static __always_inline void count_tx(u32 protocol)
37 {
38 u64 *rxcnt_count;
39
40 rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
41 if (rxcnt_count)
42 *rxcnt_count += 1;
43 }
44
45 static __always_inline int get_dport(void *trans_data, void *data_end,
46 u8 protocol)
47 {
48 struct tcphdr *th;
49 struct udphdr *uh;
50
51 switch (protocol) {
52 case IPPROTO_TCP:
53 th = (struct tcphdr *)trans_data;
54 if (th + 1 > data_end)
55 return -1;
56 return th->dest;
57 case IPPROTO_UDP:
58 uh = (struct udphdr *)trans_data;
59 if (uh + 1 > data_end)
60 return -1;
61 return uh->dest;
62 default:
63 return 0;
64 }
65 }
66
67 static __always_inline void set_ethhdr(struct ethhdr *new_eth,
68 const struct ethhdr *old_eth,
69 const struct iptnl_info *tnl,
70 __be16 h_proto)
71 {
72 memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
73 memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
74 new_eth->h_proto = h_proto;
75 }
76
77 static __always_inline int handle_ipv4(struct xdp_md *xdp)
78 {
79 void *data_end = (void *)(long)xdp->data_end;
80 void *data = (void *)(long)xdp->data;
81 struct iptnl_info *tnl;
82 struct ethhdr *new_eth;
83 struct ethhdr *old_eth;
84 struct iphdr *iph = data + sizeof(struct ethhdr);
85 u16 *next_iph_u16;
86 u16 payload_len;
87 struct vip vip = {};
88 int dport;
89 u32 csum = 0;
90 int i;
91
92 if (iph + 1 > data_end)
93 return XDP_DROP;
94
95 dport = get_dport(iph + 1, data_end, iph->protocol);
96 if (dport == -1)
97 return XDP_DROP;
98
99 vip.protocol = iph->protocol;
100 vip.family = AF_INET;
101 vip.daddr.v4 = iph->daddr;
102 vip.dport = dport;
103 payload_len = ntohs(iph->tot_len);
104
105 tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
106 /* It only does v4-in-v4 */
107 if (!tnl || tnl->family != AF_INET)
108 return XDP_PASS;
109
110 /* The vip key is found. Add an IP header and send it out */
111
112 if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct iphdr)))
113 return XDP_DROP;
114
115 data = (void *)(long)xdp->data;
116 data_end = (void *)(long)xdp->data_end;
117
118 new_eth = data;
119 iph = data + sizeof(*new_eth);
120 old_eth = data + sizeof(*iph);
121
122 if (new_eth + 1 > data_end ||
123 old_eth + 1 > data_end ||
124 iph + 1 > data_end)
125 return XDP_DROP;
126
127 set_ethhdr(new_eth, old_eth, tnl, htons(ETH_P_IP));
128
129 iph->version = 4;
130 iph->ihl = sizeof(*iph) >> 2;
131 iph->frag_off = 0;
132 iph->protocol = IPPROTO_IPIP;
133 iph->check = 0;
134 iph->tos = 0;
135 iph->tot_len = htons(payload_len + sizeof(*iph));
136 iph->daddr = tnl->daddr.v4;
137 iph->saddr = tnl->saddr.v4;
138 iph->ttl = 8;
139
140 next_iph_u16 = (u16 *)iph;
141 #pragma clang loop unroll(full)
142 for (i = 0; i < sizeof(*iph) >> 1; i++)
143 csum += *next_iph_u16++;
144
145 iph->check = ~((csum & 0xffff) + (csum >> 16));
146
147 count_tx(vip.protocol);
148
149 return XDP_TX;
150 }
151
152 static __always_inline int handle_ipv6(struct xdp_md *xdp)
153 {
154 void *data_end = (void *)(long)xdp->data_end;
155 void *data = (void *)(long)xdp->data;
156 struct iptnl_info *tnl;
157 struct ethhdr *new_eth;
158 struct ethhdr *old_eth;
159 struct ipv6hdr *ip6h = data + sizeof(struct ethhdr);
160 __u16 payload_len;
161 struct vip vip = {};
162 int dport;
163
164 if (ip6h + 1 > data_end)
165 return XDP_DROP;
166
167 dport = get_dport(ip6h + 1, data_end, ip6h->nexthdr);
168 if (dport == -1)
169 return XDP_DROP;
170
171 vip.protocol = ip6h->nexthdr;
172 vip.family = AF_INET6;
173 memcpy(vip.daddr.v6, ip6h->daddr.s6_addr32, sizeof(vip.daddr));
174 vip.dport = dport;
175 payload_len = ip6h->payload_len;
176
177 tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
178 /* It only does v6-in-v6 */
179 if (!tnl || tnl->family != AF_INET6)
180 return XDP_PASS;
181
182 /* The vip key is found. Add an IP header and send it out */
183
184 if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct ipv6hdr)))
185 return XDP_DROP;
186
187 data = (void *)(long)xdp->data;
188 data_end = (void *)(long)xdp->data_end;
189
190 new_eth = data;
191 ip6h = data + sizeof(*new_eth);
192 old_eth = data + sizeof(*ip6h);
193
194 if (new_eth + 1 > data_end ||
195 old_eth + 1 > data_end ||
196 ip6h + 1 > data_end)
197 return XDP_DROP;
198
199 set_ethhdr(new_eth, old_eth, tnl, htons(ETH_P_IPV6));
200
201 ip6h->version = 6;
202 ip6h->priority = 0;
203 memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));
204 ip6h->payload_len = htons(ntohs(payload_len) + sizeof(*ip6h));
205 ip6h->nexthdr = IPPROTO_IPV6;
206 ip6h->hop_limit = 8;
207 memcpy(ip6h->saddr.s6_addr32, tnl->saddr.v6, sizeof(tnl->saddr.v6));
208 memcpy(ip6h->daddr.s6_addr32, tnl->daddr.v6, sizeof(tnl->daddr.v6));
209
210 count_tx(vip.protocol);
211
212 return XDP_TX;
213 }
214
215 SEC("xdp.frags")
216 int _xdp_tx_iptunnel(struct xdp_md *xdp)
217 {
218 void *data_end = (void *)(long)xdp->data_end;
219 void *data = (void *)(long)xdp->data;
220 struct ethhdr *eth = data;
221 __u16 h_proto;
222
223 if (eth + 1 > data_end)
224 return XDP_DROP;
225
226 h_proto = eth->h_proto;
227
228 if (h_proto == htons(ETH_P_IP))
229 return handle_ipv4(xdp);
230 else if (h_proto == htons(ETH_P_IPV6))
231
232 return handle_ipv6(xdp);
233 else
234 return XDP_PASS;
235 }
236
237 char _license[] SEC("license") = "GPL";
238
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