1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2017 Facebook
3 #include <stddef.h>
4 #include <stdbool.h>
5 #include <string.h>
6 #include <linux/pkt_cls.h>
7 #include <linux/bpf.h>
8 #include <linux/in.h>
9 #include <linux/if_ether.h>
10 #include <linux/ip.h>
11 #include <linux/ipv6.h>
12 #include <linux/icmp.h>
13 #include <linux/icmpv6.h>
14 #include <linux/tcp.h>
15 #include <linux/udp.h>
16 #include <bpf/bpf_helpers.h>
17 #include "test_iptunnel_common.h"
18 #include <bpf/bpf_endian.h>
19 
20 #include "bpf_kfuncs.h"
21 
22 static __always_inline __u32 rol32(__u32 word, unsigned int shift)
23 {
24 	return (word << shift) | (word >> ((-shift) & 31));
25 }
26 
27 /* copy paste of jhash from kernel sources to make sure llvm
28  * can compile it into valid sequence of bpf instructions
29  */
30 #define __jhash_mix(a, b, c)			\
31 {						\
32 	a -= c;  a ^= rol32(c, 4);  c += b;	\
33 	b -= a;  b ^= rol32(a, 6);  a += c;	\
34 	c -= b;  c ^= rol32(b, 8);  b += a;	\
35 	a -= c;  a ^= rol32(c, 16); c += b;	\
36 	b -= a;  b ^= rol32(a, 19); a += c;	\
37 	c -= b;  c ^= rol32(b, 4);  b += a;	\
38 }
39 
40 #define __jhash_final(a, b, c)			\
41 {						\
42 	c ^= b; c -= rol32(b, 14);		\
43 	a ^= c; a -= rol32(c, 11);		\
44 	b ^= a; b -= rol32(a, 25);		\
45 	c ^= b; c -= rol32(b, 16);		\
46 	a ^= c; a -= rol32(c, 4);		\
47 	b ^= a; b -= rol32(a, 14);		\
48 	c ^= b; c -= rol32(b, 24);		\
49 }
50 
51 #define JHASH_INITVAL		0xdeadbeef
52 
53 typedef unsigned int u32;
54 
55 static __noinline u32 jhash(const void *key, u32 length, u32 initval)
56 {
57 	u32 a, b, c;
58 	const unsigned char *k = key;
59 
60 	a = b = c = JHASH_INITVAL + length + initval;
61 
62 	while (length > 12) {
63 		a += *(u32 *)(k);
64 		b += *(u32 *)(k + 4);
65 		c += *(u32 *)(k + 8);
66 		__jhash_mix(a, b, c);
67 		length -= 12;
68 		k += 12;
69 	}
70 	switch (length) {
71 	case 12: c += (u32)k[11]<<24;
72 	case 11: c += (u32)k[10]<<16;
73 	case 10: c += (u32)k[9]<<8;
74 	case 9:  c += k[8];
75 	case 8:  b += (u32)k[7]<<24;
76 	case 7:  b += (u32)k[6]<<16;
77 	case 6:  b += (u32)k[5]<<8;
78 	case 5:  b += k[4];
79 	case 4:  a += (u32)k[3]<<24;
80 	case 3:  a += (u32)k[2]<<16;
81 	case 2:  a += (u32)k[1]<<8;
82 	case 1:  a += k[0];
83 		 __jhash_final(a, b, c);
84 	case 0: /* Nothing left to add */
85 		break;
86 	}
87 
88 	return c;
89 }
90 
91 static __noinline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
92 {
93 	a += initval;
94 	b += initval;
95 	c += initval;
96 	__jhash_final(a, b, c);
97 	return c;
98 }
99 
100 static __noinline u32 jhash_2words(u32 a, u32 b, u32 initval)
101 {
102 	return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
103 }
104 
105 #define PCKT_FRAGMENTED 65343
106 #define IPV4_HDR_LEN_NO_OPT 20
107 #define IPV4_PLUS_ICMP_HDR 28
108 #define IPV6_PLUS_ICMP_HDR 48
109 #define RING_SIZE 2
110 #define MAX_VIPS 12
111 #define MAX_REALS 5
112 #define CTL_MAP_SIZE 16
113 #define CH_RINGS_SIZE (MAX_VIPS * RING_SIZE)
114 #define F_IPV6 (1 << 0)
115 #define F_HASH_NO_SRC_PORT (1 << 0)
116 #define F_ICMP (1 << 0)
117 #define F_SYN_SET (1 << 1)
118 
119 struct packet_description {
120 	union {
121 		__be32 src;
122 		__be32 srcv6[4];
123 	};
124 	union {
125 		__be32 dst;
126 		__be32 dstv6[4];
127 	};
128 	union {
129 		__u32 ports;
130 		__u16 port16[2];
131 	};
132 	__u8 proto;
133 	__u8 flags;
134 };
135 
136 struct ctl_value {
137 	union {
138 		__u64 value;
139 		__u32 ifindex;
140 		__u8 mac[6];
141 	};
142 };
143 
144 struct vip_meta {
145 	__u32 flags;
146 	__u32 vip_num;
147 };
148 
149 struct real_definition {
150 	union {
151 		__be32 dst;
152 		__be32 dstv6[4];
153 	};
154 	__u8 flags;
155 };
156 
157 struct vip_stats {
158 	__u64 bytes;
159 	__u64 pkts;
160 };
161 
162 struct eth_hdr {
163 	unsigned char eth_dest[ETH_ALEN];
164 	unsigned char eth_source[ETH_ALEN];
165 	unsigned short eth_proto;
166 };
167 
168 struct {
169 	__uint(type, BPF_MAP_TYPE_HASH);
170 	__uint(max_entries, MAX_VIPS);
171 	__type(key, struct vip);
172 	__type(value, struct vip_meta);
173 } vip_map SEC(".maps");
174 
175 struct {
176 	__uint(type, BPF_MAP_TYPE_ARRAY);
177 	__uint(max_entries, CH_RINGS_SIZE);
178 	__type(key, __u32);
179 	__type(value, __u32);
180 } ch_rings SEC(".maps");
181 
182 struct {
183 	__uint(type, BPF_MAP_TYPE_ARRAY);
184 	__uint(max_entries, MAX_REALS);
185 	__type(key, __u32);
186 	__type(value, struct real_definition);
187 } reals SEC(".maps");
188 
189 struct {
190 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
191 	__uint(max_entries, MAX_VIPS);
192 	__type(key, __u32);
193 	__type(value, struct vip_stats);
194 } stats SEC(".maps");
195 
196 struct {
197 	__uint(type, BPF_MAP_TYPE_ARRAY);
198 	__uint(max_entries, CTL_MAP_SIZE);
199 	__type(key, __u32);
200 	__type(value, struct ctl_value);
201 } ctl_array SEC(".maps");
202 
203 static __noinline __u32 get_packet_hash(struct packet_description *pckt, bool ipv6)
204 {
205 	if (ipv6)
206 		return jhash_2words(jhash(pckt->srcv6, 16, MAX_VIPS),
207 				    pckt->ports, CH_RINGS_SIZE);
208 	else
209 		return jhash_2words(pckt->src, pckt->ports, CH_RINGS_SIZE);
210 }
211 
212 static __noinline bool get_packet_dst(struct real_definition **real,
213 				      struct packet_description *pckt,
214 				      struct vip_meta *vip_info,
215 				      bool is_ipv6)
216 {
217 	__u32 hash = get_packet_hash(pckt, is_ipv6);
218 	__u32 key = RING_SIZE * vip_info->vip_num + hash % RING_SIZE;
219 	__u32 *real_pos;
220 
221 	if (hash != 0x358459b7 /* jhash of ipv4 packet */  &&
222 	    hash != 0x2f4bc6bb /* jhash of ipv6 packet */)
223 		return false;
224 
225 	real_pos = bpf_map_lookup_elem(&ch_rings, &key);
226 	if (!real_pos)
227 		return false;
228 	key = *real_pos;
229 	*real = bpf_map_lookup_elem(&reals, &key);
230 	if (!(*real))
231 		return false;
232 	return true;
233 }
234 
235 static __noinline int parse_icmpv6(struct bpf_dynptr *skb_ptr, __u64 off,
236 				   struct packet_description *pckt)
237 {
238 	__u8 buffer[sizeof(struct ipv6hdr)] = {};
239 	struct icmp6hdr *icmp_hdr;
240 	struct ipv6hdr *ip6h;
241 
242 	icmp_hdr = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
243 	if (!icmp_hdr)
244 		return TC_ACT_SHOT;
245 
246 	if (icmp_hdr->icmp6_type != ICMPV6_PKT_TOOBIG)
247 		return TC_ACT_OK;
248 	off += sizeof(struct icmp6hdr);
249 	ip6h = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
250 	if (!ip6h)
251 		return TC_ACT_SHOT;
252 	pckt->proto = ip6h->nexthdr;
253 	pckt->flags |= F_ICMP;
254 	memcpy(pckt->srcv6, ip6h->daddr.s6_addr32, 16);
255 	memcpy(pckt->dstv6, ip6h->saddr.s6_addr32, 16);
256 	return TC_ACT_UNSPEC;
257 }
258 
259 static __noinline int parse_icmp(struct bpf_dynptr *skb_ptr, __u64 off,
260 				 struct packet_description *pckt)
261 {
262 	__u8 buffer_icmp[sizeof(struct iphdr)] = {};
263 	__u8 buffer_ip[sizeof(struct iphdr)] = {};
264 	struct icmphdr *icmp_hdr;
265 	struct iphdr *iph;
266 
267 	icmp_hdr = bpf_dynptr_slice(skb_ptr, off, buffer_icmp, sizeof(buffer_icmp));
268 	if (!icmp_hdr)
269 		return TC_ACT_SHOT;
270 	if (icmp_hdr->type != ICMP_DEST_UNREACH ||
271 	    icmp_hdr->code != ICMP_FRAG_NEEDED)
272 		return TC_ACT_OK;
273 	off += sizeof(struct icmphdr);
274 	iph = bpf_dynptr_slice(skb_ptr, off, buffer_ip, sizeof(buffer_ip));
275 	if (!iph || iph->ihl != 5)
276 		return TC_ACT_SHOT;
277 	pckt->proto = iph->protocol;
278 	pckt->flags |= F_ICMP;
279 	pckt->src = iph->daddr;
280 	pckt->dst = iph->saddr;
281 	return TC_ACT_UNSPEC;
282 }
283 
284 static __noinline bool parse_udp(struct bpf_dynptr *skb_ptr, __u64 off,
285 				 struct packet_description *pckt)
286 {
287 	__u8 buffer[sizeof(struct udphdr)] = {};
288 	struct udphdr *udp;
289 
290 	udp = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
291 	if (!udp)
292 		return false;
293 
294 	if (!(pckt->flags & F_ICMP)) {
295 		pckt->port16[0] = udp->source;
296 		pckt->port16[1] = udp->dest;
297 	} else {
298 		pckt->port16[0] = udp->dest;
299 		pckt->port16[1] = udp->source;
300 	}
301 	return true;
302 }
303 
304 static __noinline bool parse_tcp(struct bpf_dynptr *skb_ptr, __u64 off,
305 				 struct packet_description *pckt)
306 {
307 	__u8 buffer[sizeof(struct tcphdr)] = {};
308 	struct tcphdr *tcp;
309 
310 	tcp = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
311 	if (!tcp)
312 		return false;
313 
314 	if (tcp->syn)
315 		pckt->flags |= F_SYN_SET;
316 
317 	if (!(pckt->flags & F_ICMP)) {
318 		pckt->port16[0] = tcp->source;
319 		pckt->port16[1] = tcp->dest;
320 	} else {
321 		pckt->port16[0] = tcp->dest;
322 		pckt->port16[1] = tcp->source;
323 	}
324 	return true;
325 }
326 
327 static __noinline int process_packet(struct bpf_dynptr *skb_ptr,
328 				     struct eth_hdr *eth, __u64 off,
329 				     bool is_ipv6, struct __sk_buff *skb)
330 {
331 	struct packet_description pckt = {};
332 	struct bpf_tunnel_key tkey = {};
333 	struct vip_stats *data_stats;
334 	struct real_definition *dst;
335 	struct vip_meta *vip_info;
336 	struct ctl_value *cval;
337 	__u32 v4_intf_pos = 1;
338 	__u32 v6_intf_pos = 2;
339 	struct ipv6hdr *ip6h;
340 	struct vip vip = {};
341 	struct iphdr *iph;
342 	int tun_flag = 0;
343 	__u16 pkt_bytes;
344 	__u64 iph_len;
345 	__u32 ifindex;
346 	__u8 protocol;
347 	__u32 vip_num;
348 	int action;
349 
350 	tkey.tunnel_ttl = 64;
351 	if (is_ipv6) {
352 		__u8 buffer[sizeof(struct ipv6hdr)] = {};
353 
354 		ip6h = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
355 		if (!ip6h)
356 			return TC_ACT_SHOT;
357 
358 		iph_len = sizeof(struct ipv6hdr);
359 		protocol = ip6h->nexthdr;
360 		pckt.proto = protocol;
361 		pkt_bytes = bpf_ntohs(ip6h->payload_len);
362 		off += iph_len;
363 		if (protocol == IPPROTO_FRAGMENT) {
364 			return TC_ACT_SHOT;
365 		} else if (protocol == IPPROTO_ICMPV6) {
366 			action = parse_icmpv6(skb_ptr, off, &pckt);
367 			if (action >= 0)
368 				return action;
369 			off += IPV6_PLUS_ICMP_HDR;
370 		} else {
371 			memcpy(pckt.srcv6, ip6h->saddr.s6_addr32, 16);
372 			memcpy(pckt.dstv6, ip6h->daddr.s6_addr32, 16);
373 		}
374 	} else {
375 		__u8 buffer[sizeof(struct iphdr)] = {};
376 
377 		iph = bpf_dynptr_slice(skb_ptr, off, buffer, sizeof(buffer));
378 		if (!iph || iph->ihl != 5)
379 			return TC_ACT_SHOT;
380 
381 		protocol = iph->protocol;
382 		pckt.proto = protocol;
383 		pkt_bytes = bpf_ntohs(iph->tot_len);
384 		off += IPV4_HDR_LEN_NO_OPT;
385 
386 		if (iph->frag_off & PCKT_FRAGMENTED)
387 			return TC_ACT_SHOT;
388 		if (protocol == IPPROTO_ICMP) {
389 			action = parse_icmp(skb_ptr, off, &pckt);
390 			if (action >= 0)
391 				return action;
392 			off += IPV4_PLUS_ICMP_HDR;
393 		} else {
394 			pckt.src = iph->saddr;
395 			pckt.dst = iph->daddr;
396 		}
397 	}
398 	protocol = pckt.proto;
399 
400 	if (protocol == IPPROTO_TCP) {
401 		if (!parse_tcp(skb_ptr, off, &pckt))
402 			return TC_ACT_SHOT;
403 	} else if (protocol == IPPROTO_UDP) {
404 		if (!parse_udp(skb_ptr, off, &pckt))
405 			return TC_ACT_SHOT;
406 	} else {
407 		return TC_ACT_SHOT;
408 	}
409 
410 	if (is_ipv6)
411 		memcpy(vip.daddr.v6, pckt.dstv6, 16);
412 	else
413 		vip.daddr.v4 = pckt.dst;
414 
415 	vip.dport = pckt.port16[1];
416 	vip.protocol = pckt.proto;
417 	vip_info = bpf_map_lookup_elem(&vip_map, &vip);
418 	if (!vip_info) {
419 		vip.dport = 0;
420 		vip_info = bpf_map_lookup_elem(&vip_map, &vip);
421 		if (!vip_info)
422 			return TC_ACT_SHOT;
423 		pckt.port16[1] = 0;
424 	}
425 
426 	if (vip_info->flags & F_HASH_NO_SRC_PORT)
427 		pckt.port16[0] = 0;
428 
429 	if (!get_packet_dst(&dst, &pckt, vip_info, is_ipv6))
430 		return TC_ACT_SHOT;
431 
432 	if (dst->flags & F_IPV6) {
433 		cval = bpf_map_lookup_elem(&ctl_array, &v6_intf_pos);
434 		if (!cval)
435 			return TC_ACT_SHOT;
436 		ifindex = cval->ifindex;
437 		memcpy(tkey.remote_ipv6, dst->dstv6, 16);
438 		tun_flag = BPF_F_TUNINFO_IPV6;
439 	} else {
440 		cval = bpf_map_lookup_elem(&ctl_array, &v4_intf_pos);
441 		if (!cval)
442 			return TC_ACT_SHOT;
443 		ifindex = cval->ifindex;
444 		tkey.remote_ipv4 = dst->dst;
445 	}
446 	vip_num = vip_info->vip_num;
447 	data_stats = bpf_map_lookup_elem(&stats, &vip_num);
448 	if (!data_stats)
449 		return TC_ACT_SHOT;
450 	data_stats->pkts++;
451 	data_stats->bytes += pkt_bytes;
452 	bpf_skb_set_tunnel_key(skb, &tkey, sizeof(tkey), tun_flag);
453 	*(u32 *)eth->eth_dest = tkey.remote_ipv4;
454 	return bpf_redirect(ifindex, 0);
455 }
456 
457 SEC("tc")
458 int balancer_ingress(struct __sk_buff *ctx)
459 {
460 	__u8 buffer[sizeof(struct eth_hdr)] = {};
461 	struct bpf_dynptr ptr;
462 	struct eth_hdr *eth;
463 	__u32 eth_proto;
464 	__u32 nh_off;
465 	int err;
466 
467 	nh_off = sizeof(struct eth_hdr);
468 
469 	bpf_dynptr_from_skb(ctx, 0, &ptr);
470 	eth = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer));
471 	if (!eth)
472 		return TC_ACT_SHOT;
473 	eth_proto = eth->eth_proto;
474 	if (eth_proto == bpf_htons(ETH_P_IP))
475 		err = process_packet(&ptr, eth, nh_off, false, ctx);
476 	else if (eth_proto == bpf_htons(ETH_P_IPV6))
477 		err = process_packet(&ptr, eth, nh_off, true, ctx);
478 	else
479 		return TC_ACT_SHOT;
480 
481 	if (eth == buffer)
482 		bpf_dynptr_write(&ptr, 0, buffer, sizeof(buffer), 0);
483 
484 	return err;
485 }
486 
487 char _license[] SEC("license") = "GPL";
488