1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3 #include <stdbool.h>
4 #include <stdint.h>
5 #include <linux/stddef.h>
6 #include <linux/if_ether.h>
7 #include <linux/in.h>
8 #include <linux/in6.h>
9 #include <linux/ip.h>
10 #include <linux/ipv6.h>
11 #include <linux/tcp.h>
12 #include <linux/udp.h>
13 #include <linux/bpf.h>
14 #include <linux/types.h>
15 #include <bpf/bpf_endian.h>
16 #include <bpf/bpf_helpers.h>
17
18 enum pkt_parse_err {
19 NO_ERR,
20 BAD_IP6_HDR,
21 BAD_IP4GUE_HDR,
22 BAD_IP6GUE_HDR,
23 };
24
25 enum pkt_flag {
26 TUNNEL = 0x1,
27 TCP_SYN = 0x2,
28 QUIC_INITIAL_FLAG = 0x4,
29 TCP_ACK = 0x8,
30 TCP_RST = 0x10
31 };
32
33 struct v4_lpm_key {
34 __u32 prefixlen;
35 __u32 src;
36 };
37
38 struct v4_lpm_val {
39 struct v4_lpm_key key;
40 __u8 val;
41 };
42
43 struct {
44 __uint(type, BPF_MAP_TYPE_HASH);
45 __uint(max_entries, 16);
46 __type(key, struct in6_addr);
47 __type(value, bool);
48 } v6_addr_map SEC(".maps");
49
50 struct {
51 __uint(type, BPF_MAP_TYPE_HASH);
52 __uint(max_entries, 16);
53 __type(key, __u32);
54 __type(value, bool);
55 } v4_addr_map SEC(".maps");
56
57 struct {
58 __uint(type, BPF_MAP_TYPE_LPM_TRIE);
59 __uint(max_entries, 16);
60 __uint(key_size, sizeof(struct v4_lpm_key));
61 __uint(value_size, sizeof(struct v4_lpm_val));
62 __uint(map_flags, BPF_F_NO_PREALLOC);
63 } v4_lpm_val_map SEC(".maps");
64
65 struct {
66 __uint(type, BPF_MAP_TYPE_ARRAY);
67 __uint(max_entries, 16);
68 __type(key, int);
69 __type(value, __u8);
70 } tcp_port_map SEC(".maps");
71
72 struct {
73 __uint(type, BPF_MAP_TYPE_ARRAY);
74 __uint(max_entries, 16);
75 __type(key, int);
76 __type(value, __u16);
77 } udp_port_map SEC(".maps");
78
79 enum ip_type { V4 = 1, V6 = 2 };
80
81 struct fw_match_info {
82 __u8 v4_src_ip_match;
83 __u8 v6_src_ip_match;
84 __u8 v4_src_prefix_match;
85 __u8 v4_dst_prefix_match;
86 __u8 tcp_dp_match;
87 __u16 udp_sp_match;
88 __u16 udp_dp_match;
89 bool is_tcp;
90 bool is_tcp_syn;
91 };
92
93 struct pkt_info {
94 enum ip_type type;
95 union {
96 struct iphdr *ipv4;
97 struct ipv6hdr *ipv6;
98 } ip;
99 int sport;
100 int dport;
101 __u16 trans_hdr_offset;
102 __u8 proto;
103 __u8 flags;
104 };
105
106 static __always_inline struct ethhdr *parse_ethhdr(void *data, void *data_end)
107 {
108 struct ethhdr *eth = data;
109
110 if (eth + 1 > data_end)
111 return NULL;
112
113 return eth;
114 }
115
116 static __always_inline __u8 filter_ipv6_addr(const struct in6_addr *ipv6addr)
117 {
118 __u8 *leaf;
119
120 leaf = bpf_map_lookup_elem(&v6_addr_map, ipv6addr);
121
122 return leaf ? *leaf : 0;
123 }
124
125 static __always_inline __u8 filter_ipv4_addr(const __u32 ipaddr)
126 {
127 __u8 *leaf;
128
129 leaf = bpf_map_lookup_elem(&v4_addr_map, &ipaddr);
130
131 return leaf ? *leaf : 0;
132 }
133
134 static __always_inline __u8 filter_ipv4_lpm(const __u32 ipaddr)
135 {
136 struct v4_lpm_key v4_key = {};
137 struct v4_lpm_val *lpm_val;
138
139 v4_key.src = ipaddr;
140 v4_key.prefixlen = 32;
141
142 lpm_val = bpf_map_lookup_elem(&v4_lpm_val_map, &v4_key);
143
144 return lpm_val ? lpm_val->val : 0;
145 }
146
147
148 static __always_inline void
149 filter_src_dst_ip(struct pkt_info* info, struct fw_match_info* match_info)
150 {
151 if (info->type == V6) {
152 match_info->v6_src_ip_match =
153 filter_ipv6_addr(&info->ip.ipv6->saddr);
154 } else if (info->type == V4) {
155 match_info->v4_src_ip_match =
156 filter_ipv4_addr(info->ip.ipv4->saddr);
157 match_info->v4_src_prefix_match =
158 filter_ipv4_lpm(info->ip.ipv4->saddr);
159 match_info->v4_dst_prefix_match =
160 filter_ipv4_lpm(info->ip.ipv4->daddr);
161 }
162 }
163
164 static __always_inline void *
165 get_transport_hdr(__u16 offset, void *data, void *data_end)
166 {
167 if (offset > 255 || data + offset > data_end)
168 return NULL;
169
170 return data + offset;
171 }
172
173 static __always_inline bool tcphdr_only_contains_flag(struct tcphdr *tcp,
174 __u32 FLAG)
175 {
176 return (tcp_flag_word(tcp) &
177 (TCP_FLAG_ACK | TCP_FLAG_RST | TCP_FLAG_SYN | TCP_FLAG_FIN)) == FLAG;
178 }
179
180 static __always_inline void set_tcp_flags(struct pkt_info *info,
181 struct tcphdr *tcp) {
182 if (tcphdr_only_contains_flag(tcp, TCP_FLAG_SYN))
183 info->flags |= TCP_SYN;
184 else if (tcphdr_only_contains_flag(tcp, TCP_FLAG_ACK))
185 info->flags |= TCP_ACK;
186 else if (tcphdr_only_contains_flag(tcp, TCP_FLAG_RST))
187 info->flags |= TCP_RST;
188 }
189
190 static __always_inline bool
191 parse_tcp(struct pkt_info *info, void *transport_hdr, void *data_end)
192 {
193 struct tcphdr *tcp = transport_hdr;
194
195 if (tcp + 1 > data_end)
196 return false;
197
198 info->sport = bpf_ntohs(tcp->source);
199 info->dport = bpf_ntohs(tcp->dest);
200 set_tcp_flags(info, tcp);
201
202 return true;
203 }
204
205 static __always_inline bool
206 parse_udp(struct pkt_info *info, void *transport_hdr, void *data_end)
207 {
208 struct udphdr *udp = transport_hdr;
209
210 if (udp + 1 > data_end)
211 return false;
212
213 info->sport = bpf_ntohs(udp->source);
214 info->dport = bpf_ntohs(udp->dest);
215
216 return true;
217 }
218
219 static __always_inline __u8 filter_tcp_port(int port)
220 {
221 __u8 *leaf = bpf_map_lookup_elem(&tcp_port_map, &port);
222
223 return leaf ? *leaf : 0;
224 }
225
226 static __always_inline __u16 filter_udp_port(int port)
227 {
228 __u16 *leaf = bpf_map_lookup_elem(&udp_port_map, &port);
229
230 return leaf ? *leaf : 0;
231 }
232
233 static __always_inline bool
234 filter_transport_hdr(void *transport_hdr, void *data_end,
235 struct pkt_info *info, struct fw_match_info *match_info)
236 {
237 if (info->proto == IPPROTO_TCP) {
238 if (!parse_tcp(info, transport_hdr, data_end))
239 return false;
240
241 match_info->is_tcp = true;
242 match_info->is_tcp_syn = (info->flags & TCP_SYN) > 0;
243
244 match_info->tcp_dp_match = filter_tcp_port(info->dport);
245 } else if (info->proto == IPPROTO_UDP) {
246 if (!parse_udp(info, transport_hdr, data_end))
247 return false;
248
249 match_info->udp_dp_match = filter_udp_port(info->dport);
250 match_info->udp_sp_match = filter_udp_port(info->sport);
251 }
252
253 return true;
254 }
255
256 static __always_inline __u8
257 parse_gue_v6(struct pkt_info *info, struct ipv6hdr *ip6h, void *data_end)
258 {
259 struct udphdr *udp = (struct udphdr *)(ip6h + 1);
260 void *encap_data = udp + 1;
261
262 if (udp + 1 > data_end)
263 return BAD_IP6_HDR;
264
265 if (udp->dest != bpf_htons(6666))
266 return NO_ERR;
267
268 info->flags |= TUNNEL;
269
270 if (encap_data + 1 > data_end)
271 return BAD_IP6GUE_HDR;
272
273 if (*(__u8 *)encap_data & 0x30) {
274 struct ipv6hdr *inner_ip6h = encap_data;
275
276 if (inner_ip6h + 1 > data_end)
277 return BAD_IP6GUE_HDR;
278
279 info->type = V6;
280 info->proto = inner_ip6h->nexthdr;
281 info->ip.ipv6 = inner_ip6h;
282 info->trans_hdr_offset += sizeof(struct ipv6hdr) + sizeof(struct udphdr);
283 } else {
284 struct iphdr *inner_ip4h = encap_data;
285
286 if (inner_ip4h + 1 > data_end)
287 return BAD_IP6GUE_HDR;
288
289 info->type = V4;
290 info->proto = inner_ip4h->protocol;
291 info->ip.ipv4 = inner_ip4h;
292 info->trans_hdr_offset += sizeof(struct iphdr) + sizeof(struct udphdr);
293 }
294
295 return NO_ERR;
296 }
297
298 static __always_inline __u8 parse_ipv6_gue(struct pkt_info *info,
299 void *data, void *data_end)
300 {
301 struct ipv6hdr *ip6h = data + sizeof(struct ethhdr);
302
303 if (ip6h + 1 > data_end)
304 return BAD_IP6_HDR;
305
306 info->proto = ip6h->nexthdr;
307 info->ip.ipv6 = ip6h;
308 info->type = V6;
309 info->trans_hdr_offset = sizeof(struct ethhdr) + sizeof(struct ipv6hdr);
310
311 if (info->proto == IPPROTO_UDP)
312 return parse_gue_v6(info, ip6h, data_end);
313
314 return NO_ERR;
315 }
316
317 SEC("xdp")
318 int edgewall(struct xdp_md *ctx)
319 {
320 void *data_end = (void *)(long)(ctx->data_end);
321 void *data = (void *)(long)(ctx->data);
322 struct fw_match_info match_info = {};
323 struct pkt_info info = {};
324 void *transport_hdr;
325 struct ethhdr *eth;
326 bool filter_res;
327 __u32 proto;
328
329 eth = parse_ethhdr(data, data_end);
330 if (!eth)
331 return XDP_DROP;
332
333 proto = eth->h_proto;
334 if (proto != bpf_htons(ETH_P_IPV6))
335 return XDP_DROP;
336
337 if (parse_ipv6_gue(&info, data, data_end))
338 return XDP_DROP;
339
340 if (info.proto == IPPROTO_ICMPV6)
341 return XDP_PASS;
342
343 if (info.proto != IPPROTO_TCP && info.proto != IPPROTO_UDP)
344 return XDP_DROP;
345
346 filter_src_dst_ip(&info, &match_info);
347
348 transport_hdr = get_transport_hdr(info.trans_hdr_offset, data,
349 data_end);
350 if (!transport_hdr)
351 return XDP_DROP;
352
353 filter_res = filter_transport_hdr(transport_hdr, data_end,
354 &info, &match_info);
355 if (!filter_res)
356 return XDP_DROP;
357
358 if (match_info.is_tcp && !match_info.is_tcp_syn)
359 return XDP_PASS;
360
361 return XDP_DROP;
362 }
363
364 char LICENSE[] SEC("license") = "GPL";
365
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