1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2019 Facebook
3 #include <stddef.h>
4 #include <string.h>
5 #include <linux/bpf.h>
6 #include <linux/if_ether.h>
7 #include <linux/if_packet.h>
8 #include <linux/ip.h>
9 #include <linux/ipv6.h>
10 #include <linux/in.h>
11 #include <linux/udp.h>
12 #include <linux/tcp.h>
13 #include <linux/pkt_cls.h>
14 #include <sys/socket.h>
15 #include <bpf/bpf_helpers.h>
16 #include <bpf/bpf_endian.h>
17 #include "test_iptunnel_common.h"
18 
19 struct {
20 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
21 	__uint(max_entries, 256);
22 	__type(key, __u32);
23 	__type(value, __u64);
24 } rxcnt SEC(".maps");
25 
26 struct {
27 	__uint(type, BPF_MAP_TYPE_HASH);
28 	__uint(max_entries, MAX_IPTNL_ENTRIES);
29 	__type(key, struct vip);
30 	__type(value, struct iptnl_info);
31 } vip2tnl SEC(".maps");
32 
33 static __always_inline void count_tx(__u32 protocol)
34 {
35 	__u64 *rxcnt_count;
36 
37 	rxcnt_count = bpf_map_lookup_elem(&rxcnt, &protocol);
38 	if (rxcnt_count)
39 		*rxcnt_count += 1;
40 }
41 
42 static __always_inline int get_dport(void *trans_data, void *data_end,
43 				     __u8 protocol)
44 {
45 	struct tcphdr *th;
46 	struct udphdr *uh;
47 
48 	switch (protocol) {
49 	case IPPROTO_TCP:
50 		th = (struct tcphdr *)trans_data;
51 		if (th + 1 > data_end)
52 			return -1;
53 		return th->dest;
54 	case IPPROTO_UDP:
55 		uh = (struct udphdr *)trans_data;
56 		if (uh + 1 > data_end)
57 			return -1;
58 		return uh->dest;
59 	default:
60 		return 0;
61 	}
62 }
63 
64 static __always_inline void set_ethhdr(struct ethhdr *new_eth,
65 				       const struct ethhdr *old_eth,
66 				       const struct iptnl_info *tnl,
67 				       __be16 h_proto)
68 {
69 	memcpy(new_eth->h_source, old_eth->h_dest, sizeof(new_eth->h_source));
70 	memcpy(new_eth->h_dest, tnl->dmac, sizeof(new_eth->h_dest));
71 	new_eth->h_proto = h_proto;
72 }
73 
74 static __always_inline int handle_ipv4(struct xdp_md *xdp)
75 {
76 	void *data_end = (void *)(long)xdp->data_end;
77 	void *data = (void *)(long)xdp->data;
78 	struct iptnl_info *tnl;
79 	struct ethhdr *new_eth;
80 	struct ethhdr *old_eth;
81 	struct iphdr *iph = data + sizeof(struct ethhdr);
82 	__u16 *next_iph;
83 	__u16 payload_len;
84 	struct vip vip = {};
85 	int dport;
86 	__u32 csum = 0;
87 	int i;
88 
89 	if (iph + 1 > data_end)
90 		return XDP_DROP;
91 
92 	dport = get_dport(iph + 1, data_end, iph->protocol);
93 	if (dport == -1)
94 		return XDP_DROP;
95 
96 	vip.protocol = iph->protocol;
97 	vip.family = AF_INET;
98 	vip.daddr.v4 = iph->daddr;
99 	vip.dport = dport;
100 	payload_len = bpf_ntohs(iph->tot_len);
101 
102 	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
103 	/* It only does v4-in-v4 */
104 	if (!tnl || tnl->family != AF_INET)
105 		return XDP_PASS;
106 
107 	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct iphdr)))
108 		return XDP_DROP;
109 
110 	data = (void *)(long)xdp->data;
111 	data_end = (void *)(long)xdp->data_end;
112 
113 	new_eth = data;
114 	iph = data + sizeof(*new_eth);
115 	old_eth = data + sizeof(*iph);
116 
117 	if (new_eth + 1 > data_end ||
118 	    old_eth + 1 > data_end ||
119 	    iph + 1 > data_end)
120 		return XDP_DROP;
121 
122 	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IP));
123 
124 	iph->version = 4;
125 	iph->ihl = sizeof(*iph) >> 2;
126 	iph->frag_off =	0;
127 	iph->protocol = IPPROTO_IPIP;
128 	iph->check = 0;
129 	iph->tos = 0;
130 	iph->tot_len = bpf_htons(payload_len + sizeof(*iph));
131 	iph->daddr = tnl->daddr.v4;
132 	iph->saddr = tnl->saddr.v4;
133 	iph->ttl = 8;
134 
135 	next_iph = (__u16 *)iph;
136 #pragma clang loop unroll(disable)
137 	for (i = 0; i < sizeof(*iph) >> 1; i++)
138 		csum += *next_iph++;
139 
140 	iph->check = ~((csum & 0xffff) + (csum >> 16));
141 
142 	count_tx(vip.protocol);
143 
144 	return XDP_TX;
145 }
146 
147 static __always_inline int handle_ipv6(struct xdp_md *xdp)
148 {
149 	void *data_end = (void *)(long)xdp->data_end;
150 	void *data = (void *)(long)xdp->data;
151 	struct iptnl_info *tnl;
152 	struct ethhdr *new_eth;
153 	struct ethhdr *old_eth;
154 	struct ipv6hdr *ip6h = data + sizeof(struct ethhdr);
155 	__u16 payload_len;
156 	struct vip vip = {};
157 	int dport;
158 
159 	if (ip6h + 1 > data_end)
160 		return XDP_DROP;
161 
162 	dport = get_dport(ip6h + 1, data_end, ip6h->nexthdr);
163 	if (dport == -1)
164 		return XDP_DROP;
165 
166 	vip.protocol = ip6h->nexthdr;
167 	vip.family = AF_INET6;
168 	memcpy(vip.daddr.v6, ip6h->daddr.s6_addr32, sizeof(vip.daddr));
169 	vip.dport = dport;
170 	payload_len = ip6h->payload_len;
171 
172 	tnl = bpf_map_lookup_elem(&vip2tnl, &vip);
173 	/* It only does v6-in-v6 */
174 	if (!tnl || tnl->family != AF_INET6)
175 		return XDP_PASS;
176 
177 	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct ipv6hdr)))
178 		return XDP_DROP;
179 
180 	data = (void *)(long)xdp->data;
181 	data_end = (void *)(long)xdp->data_end;
182 
183 	new_eth = data;
184 	ip6h = data + sizeof(*new_eth);
185 	old_eth = data + sizeof(*ip6h);
186 
187 	if (new_eth + 1 > data_end || old_eth + 1 > data_end ||
188 	    ip6h + 1 > data_end)
189 		return XDP_DROP;
190 
191 	set_ethhdr(new_eth, old_eth, tnl, bpf_htons(ETH_P_IPV6));
192 
193 	ip6h->version = 6;
194 	ip6h->priority = 0;
195 	memset(ip6h->flow_lbl, 0, sizeof(ip6h->flow_lbl));
196 	ip6h->payload_len = bpf_htons(bpf_ntohs(payload_len) + sizeof(*ip6h));
197 	ip6h->nexthdr = IPPROTO_IPV6;
198 	ip6h->hop_limit = 8;
199 	memcpy(ip6h->saddr.s6_addr32, tnl->saddr.v6, sizeof(tnl->saddr.v6));
200 	memcpy(ip6h->daddr.s6_addr32, tnl->daddr.v6, sizeof(tnl->daddr.v6));
201 
202 	count_tx(vip.protocol);
203 
204 	return XDP_TX;
205 }
206 
207 SEC("xdp")
208 int _xdp_tx_iptunnel(struct xdp_md *xdp)
209 {
210 	void *data_end = (void *)(long)xdp->data_end;
211 	void *data = (void *)(long)xdp->data;
212 	struct ethhdr *eth = data;
213 	__u16 h_proto;
214 
215 	if (eth + 1 > data_end)
216 		return XDP_DROP;
217 
218 	h_proto = eth->h_proto;
219 
220 	if (h_proto == bpf_htons(ETH_P_IP))
221 		return handle_ipv4(xdp);
222 	else if (h_proto == bpf_htons(ETH_P_IPV6))
223 
224 		return handle_ipv6(xdp);
225 	else
226 		return XDP_DROP;
227 }
228 
229 char _license[] SEC("license") = "GPL";
230