1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * ip_vs_xmit.c: various packet transmitters for IPVS
4  *
5  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
6  *              Julian Anastasov <ja@ssi.bg>
7  *
8  * Changes:
9  *
10  * Description of forwarding methods:
11  * - all transmitters are called from LOCAL_IN (remote clients) and
12  * LOCAL_OUT (local clients) but for ICMP can be called from FORWARD
13  * - not all connections have destination server, for example,
14  * connections in backup server when fwmark is used
15  * - bypass connections use daddr from packet
16  * - we can use dst without ref while sending in RCU section, we use
17  * ref when returning NF_ACCEPT for NAT-ed packet via loopback
18  * LOCAL_OUT rules:
19  * - skb->dev is NULL, skb->protocol is not set (both are set in POST_ROUTING)
20  * - skb->pkt_type is not set yet
21  * - the only place where we can see skb->sk != NULL
22  */
23 
24 #define KMSG_COMPONENT "IPVS"
25 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
26 
27 #include <linux/kernel.h>
28 #include <linux/slab.h>
29 #include <linux/tcp.h>                  /* for tcphdr */
30 #include <net/ip.h>
31 #include <net/gue.h>
32 #include <net/gre.h>
33 #include <net/tcp.h>                    /* for csum_tcpudp_magic */
34 #include <net/udp.h>
35 #include <net/icmp.h>                   /* for icmp_send */
36 #include <net/route.h>                  /* for ip_route_output */
37 #include <net/ipv6.h>
38 #include <net/ip6_route.h>
39 #include <net/ip_tunnels.h>
40 #include <net/ip6_checksum.h>
41 #include <net/addrconf.h>
42 #include <linux/icmpv6.h>
43 #include <linux/netfilter.h>
44 #include <linux/netfilter_ipv4.h>
45 
46 #include <net/ip_vs.h>
47 
48 enum {
49 	IP_VS_RT_MODE_LOCAL	= 1, /* Allow local dest */
50 	IP_VS_RT_MODE_NON_LOCAL	= 2, /* Allow non-local dest */
51 	IP_VS_RT_MODE_RDR	= 4, /* Allow redirect from remote daddr to
52 				      * local
53 				      */
54 	IP_VS_RT_MODE_CONNECT	= 8, /* Always bind route to saddr */
55 	IP_VS_RT_MODE_KNOWN_NH	= 16,/* Route via remote addr */
56 	IP_VS_RT_MODE_TUNNEL	= 32,/* Tunnel mode */
57 };
58 
ip_vs_dest_dst_alloc(void)59 static inline struct ip_vs_dest_dst *ip_vs_dest_dst_alloc(void)
60 {
61 	return kmalloc(sizeof(struct ip_vs_dest_dst), GFP_ATOMIC);
62 }
63 
ip_vs_dest_dst_free(struct ip_vs_dest_dst * dest_dst)64 static inline void ip_vs_dest_dst_free(struct ip_vs_dest_dst *dest_dst)
65 {
66 	kfree(dest_dst);
67 }
68 
69 /*
70  *      Destination cache to speed up outgoing route lookup
71  */
72 static inline void
__ip_vs_dst_set(struct ip_vs_dest * dest,struct ip_vs_dest_dst * dest_dst,struct dst_entry * dst,u32 dst_cookie)73 __ip_vs_dst_set(struct ip_vs_dest *dest, struct ip_vs_dest_dst *dest_dst,
74 		struct dst_entry *dst, u32 dst_cookie)
75 {
76 	struct ip_vs_dest_dst *old;
77 
78 	old = rcu_dereference_protected(dest->dest_dst,
79 					lockdep_is_held(&dest->dst_lock));
80 
81 	if (dest_dst) {
82 		dest_dst->dst_cache = dst;
83 		dest_dst->dst_cookie = dst_cookie;
84 	}
85 	rcu_assign_pointer(dest->dest_dst, dest_dst);
86 
87 	if (old)
88 		call_rcu(&old->rcu_head, ip_vs_dest_dst_rcu_free);
89 }
90 
91 static inline struct ip_vs_dest_dst *
__ip_vs_dst_check(struct ip_vs_dest * dest)92 __ip_vs_dst_check(struct ip_vs_dest *dest)
93 {
94 	struct ip_vs_dest_dst *dest_dst = rcu_dereference(dest->dest_dst);
95 	struct dst_entry *dst;
96 
97 	if (!dest_dst)
98 		return NULL;
99 	dst = dest_dst->dst_cache;
100 	if (dst->obsolete &&
101 	    dst->ops->check(dst, dest_dst->dst_cookie) == NULL)
102 		return NULL;
103 	return dest_dst;
104 }
105 
106 static inline bool
__mtu_check_toobig_v6(const struct sk_buff * skb,u32 mtu)107 __mtu_check_toobig_v6(const struct sk_buff *skb, u32 mtu)
108 {
109 	if (IP6CB(skb)->frag_max_size) {
110 		/* frag_max_size tell us that, this packet have been
111 		 * defragmented by netfilter IPv6 conntrack module.
112 		 */
113 		if (IP6CB(skb)->frag_max_size > mtu)
114 			return true; /* largest fragment violate MTU */
115 	}
116 	else if (skb->len > mtu && !skb_is_gso(skb)) {
117 		return true; /* Packet size violate MTU size */
118 	}
119 	return false;
120 }
121 
122 /* Get route to daddr, update *saddr, optionally bind route to saddr */
do_output_route4(struct net * net,__be32 daddr,int rt_mode,__be32 * saddr)123 static struct rtable *do_output_route4(struct net *net, __be32 daddr,
124 				       int rt_mode, __be32 *saddr)
125 {
126 	struct flowi4 fl4;
127 	struct rtable *rt;
128 	bool loop = false;
129 
130 	memset(&fl4, 0, sizeof(fl4));
131 	fl4.daddr = daddr;
132 	fl4.flowi4_flags = (rt_mode & IP_VS_RT_MODE_KNOWN_NH) ?
133 			   FLOWI_FLAG_KNOWN_NH : 0;
134 
135 retry:
136 	rt = ip_route_output_key(net, &fl4);
137 	if (IS_ERR(rt)) {
138 		/* Invalid saddr ? */
139 		if (PTR_ERR(rt) == -EINVAL && *saddr &&
140 		    rt_mode & IP_VS_RT_MODE_CONNECT && !loop) {
141 			*saddr = 0;
142 			flowi4_update_output(&fl4, 0, 0, daddr, 0);
143 			goto retry;
144 		}
145 		IP_VS_DBG_RL("ip_route_output error, dest: %pI4\n", &daddr);
146 		return NULL;
147 	} else if (!*saddr && rt_mode & IP_VS_RT_MODE_CONNECT && fl4.saddr) {
148 		ip_rt_put(rt);
149 		*saddr = fl4.saddr;
150 		flowi4_update_output(&fl4, 0, 0, daddr, fl4.saddr);
151 		loop = true;
152 		goto retry;
153 	}
154 	*saddr = fl4.saddr;
155 	return rt;
156 }
157 
158 #ifdef CONFIG_IP_VS_IPV6
__ip_vs_is_local_route6(struct rt6_info * rt)159 static inline int __ip_vs_is_local_route6(struct rt6_info *rt)
160 {
161 	return rt->dst.dev && rt->dst.dev->flags & IFF_LOOPBACK;
162 }
163 #endif
164 
crosses_local_route_boundary(int skb_af,struct sk_buff * skb,int rt_mode,bool new_rt_is_local)165 static inline bool crosses_local_route_boundary(int skb_af, struct sk_buff *skb,
166 						int rt_mode,
167 						bool new_rt_is_local)
168 {
169 	bool rt_mode_allow_local = !!(rt_mode & IP_VS_RT_MODE_LOCAL);
170 	bool rt_mode_allow_non_local = !!(rt_mode & IP_VS_RT_MODE_NON_LOCAL);
171 	bool rt_mode_allow_redirect = !!(rt_mode & IP_VS_RT_MODE_RDR);
172 	bool source_is_loopback;
173 	bool old_rt_is_local;
174 
175 #ifdef CONFIG_IP_VS_IPV6
176 	if (skb_af == AF_INET6) {
177 		int addr_type = ipv6_addr_type(&ipv6_hdr(skb)->saddr);
178 
179 		source_is_loopback =
180 			(!skb->dev || skb->dev->flags & IFF_LOOPBACK) &&
181 			(addr_type & IPV6_ADDR_LOOPBACK);
182 		old_rt_is_local = __ip_vs_is_local_route6(
183 			(struct rt6_info *)skb_dst(skb));
184 	} else
185 #endif
186 	{
187 		source_is_loopback = ipv4_is_loopback(ip_hdr(skb)->saddr);
188 		old_rt_is_local = skb_rtable(skb)->rt_flags & RTCF_LOCAL;
189 	}
190 
191 	if (unlikely(new_rt_is_local)) {
192 		if (!rt_mode_allow_local)
193 			return true;
194 		if (!rt_mode_allow_redirect && !old_rt_is_local)
195 			return true;
196 	} else {
197 		if (!rt_mode_allow_non_local)
198 			return true;
199 		if (source_is_loopback)
200 			return true;
201 	}
202 	return false;
203 }
204 
maybe_update_pmtu(int skb_af,struct sk_buff * skb,int mtu)205 static inline void maybe_update_pmtu(int skb_af, struct sk_buff *skb, int mtu)
206 {
207 	struct sock *sk = skb->sk;
208 	struct rtable *ort = skb_rtable(skb);
209 
210 	if (!skb->dev && sk && sk_fullsock(sk))
211 		ort->dst.ops->update_pmtu(&ort->dst, sk, NULL, mtu, true);
212 }
213 
ensure_mtu_is_adequate(struct netns_ipvs * ipvs,int skb_af,int rt_mode,struct ip_vs_iphdr * ipvsh,struct sk_buff * skb,int mtu)214 static inline bool ensure_mtu_is_adequate(struct netns_ipvs *ipvs, int skb_af,
215 					  int rt_mode,
216 					  struct ip_vs_iphdr *ipvsh,
217 					  struct sk_buff *skb, int mtu)
218 {
219 #ifdef CONFIG_IP_VS_IPV6
220 	if (skb_af == AF_INET6) {
221 		struct net *net = ipvs->net;
222 
223 		if (unlikely(__mtu_check_toobig_v6(skb, mtu))) {
224 			if (!skb->dev)
225 				skb->dev = net->loopback_dev;
226 			/* only send ICMP too big on first fragment */
227 			if (!ipvsh->fragoffs && !ip_vs_iph_icmp(ipvsh))
228 				icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
229 			IP_VS_DBG(1, "frag needed for %pI6c\n",
230 				  &ipv6_hdr(skb)->saddr);
231 			return false;
232 		}
233 	} else
234 #endif
235 	{
236 		/* If we're going to tunnel the packet and pmtu discovery
237 		 * is disabled, we'll just fragment it anyway
238 		 */
239 		if ((rt_mode & IP_VS_RT_MODE_TUNNEL) && !sysctl_pmtu_disc(ipvs))
240 			return true;
241 
242 		if (unlikely(ip_hdr(skb)->frag_off & htons(IP_DF) &&
243 			     skb->len > mtu && !skb_is_gso(skb) &&
244 			     !ip_vs_iph_icmp(ipvsh))) {
245 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
246 				  htonl(mtu));
247 			IP_VS_DBG(1, "frag needed for %pI4\n",
248 				  &ip_hdr(skb)->saddr);
249 			return false;
250 		}
251 	}
252 
253 	return true;
254 }
255 
decrement_ttl(struct netns_ipvs * ipvs,int skb_af,struct sk_buff * skb)256 static inline bool decrement_ttl(struct netns_ipvs *ipvs,
257 				 int skb_af,
258 				 struct sk_buff *skb)
259 {
260 	struct net *net = ipvs->net;
261 
262 #ifdef CONFIG_IP_VS_IPV6
263 	if (skb_af == AF_INET6) {
264 		struct dst_entry *dst = skb_dst(skb);
265 
266 		/* check and decrement ttl */
267 		if (ipv6_hdr(skb)->hop_limit <= 1) {
268 			struct inet6_dev *idev = __in6_dev_get_safely(skb->dev);
269 
270 			/* Force OUTPUT device used as source address */
271 			skb->dev = dst->dev;
272 			icmpv6_send(skb, ICMPV6_TIME_EXCEED,
273 				    ICMPV6_EXC_HOPLIMIT, 0);
274 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
275 
276 			return false;
277 		}
278 
279 		/* don't propagate ttl change to cloned packets */
280 		if (skb_ensure_writable(skb, sizeof(struct ipv6hdr)))
281 			return false;
282 
283 		ipv6_hdr(skb)->hop_limit--;
284 	} else
285 #endif
286 	{
287 		if (ip_hdr(skb)->ttl <= 1) {
288 			/* Tell the sender its packet died... */
289 			__IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
290 			icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
291 			return false;
292 		}
293 
294 		/* don't propagate ttl change to cloned packets */
295 		if (skb_ensure_writable(skb, sizeof(struct iphdr)))
296 			return false;
297 
298 		/* Decrease ttl */
299 		ip_decrease_ttl(ip_hdr(skb));
300 	}
301 
302 	return true;
303 }
304 
305 /* Get route to destination or remote server */
306 static int
__ip_vs_get_out_rt(struct netns_ipvs * ipvs,int skb_af,struct sk_buff * skb,struct ip_vs_dest * dest,__be32 daddr,int rt_mode,__be32 * ret_saddr,struct ip_vs_iphdr * ipvsh)307 __ip_vs_get_out_rt(struct netns_ipvs *ipvs, int skb_af, struct sk_buff *skb,
308 		   struct ip_vs_dest *dest,
309 		   __be32 daddr, int rt_mode, __be32 *ret_saddr,
310 		   struct ip_vs_iphdr *ipvsh)
311 {
312 	struct net *net = ipvs->net;
313 	struct ip_vs_dest_dst *dest_dst;
314 	struct rtable *rt;			/* Route to the other host */
315 	int mtu;
316 	int local, noref = 1;
317 
318 	if (dest) {
319 		dest_dst = __ip_vs_dst_check(dest);
320 		if (likely(dest_dst))
321 			rt = (struct rtable *) dest_dst->dst_cache;
322 		else {
323 			dest_dst = ip_vs_dest_dst_alloc();
324 			spin_lock_bh(&dest->dst_lock);
325 			if (!dest_dst) {
326 				__ip_vs_dst_set(dest, NULL, NULL, 0);
327 				spin_unlock_bh(&dest->dst_lock);
328 				goto err_unreach;
329 			}
330 			rt = do_output_route4(net, dest->addr.ip, rt_mode,
331 					      &dest_dst->dst_saddr.ip);
332 			if (!rt) {
333 				__ip_vs_dst_set(dest, NULL, NULL, 0);
334 				spin_unlock_bh(&dest->dst_lock);
335 				ip_vs_dest_dst_free(dest_dst);
336 				goto err_unreach;
337 			}
338 			__ip_vs_dst_set(dest, dest_dst, &rt->dst, 0);
339 			spin_unlock_bh(&dest->dst_lock);
340 			IP_VS_DBG(10, "new dst %pI4, src %pI4, refcnt=%d\n",
341 				  &dest->addr.ip, &dest_dst->dst_saddr.ip,
342 				  atomic_read(&rt->dst.__refcnt));
343 		}
344 		if (ret_saddr)
345 			*ret_saddr = dest_dst->dst_saddr.ip;
346 	} else {
347 		__be32 saddr = htonl(INADDR_ANY);
348 
349 		noref = 0;
350 
351 		/* For such unconfigured boxes avoid many route lookups
352 		 * for performance reasons because we do not remember saddr
353 		 */
354 		rt_mode &= ~IP_VS_RT_MODE_CONNECT;
355 		rt = do_output_route4(net, daddr, rt_mode, &saddr);
356 		if (!rt)
357 			goto err_unreach;
358 		if (ret_saddr)
359 			*ret_saddr = saddr;
360 	}
361 
362 	local = (rt->rt_flags & RTCF_LOCAL) ? 1 : 0;
363 	if (unlikely(crosses_local_route_boundary(skb_af, skb, rt_mode,
364 						  local))) {
365 		IP_VS_DBG_RL("We are crossing local and non-local addresses"
366 			     " daddr=%pI4\n", &daddr);
367 		goto err_put;
368 	}
369 
370 	if (unlikely(local)) {
371 		/* skb to local stack, preserve old route */
372 		if (!noref)
373 			ip_rt_put(rt);
374 		return local;
375 	}
376 
377 	if (!decrement_ttl(ipvs, skb_af, skb))
378 		goto err_put;
379 
380 	if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL))) {
381 		mtu = dst_mtu(&rt->dst);
382 	} else {
383 		mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr);
384 		if (!dest)
385 			goto err_put;
386 		if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
387 			mtu -= sizeof(struct udphdr) + sizeof(struct guehdr);
388 			if ((dest->tun_flags &
389 			     IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
390 			    skb->ip_summed == CHECKSUM_PARTIAL)
391 				mtu -= GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
392 		} else if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
393 			__be16 tflags = 0;
394 
395 			if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
396 				tflags |= TUNNEL_CSUM;
397 			mtu -= gre_calc_hlen(tflags);
398 		}
399 		if (mtu < 68) {
400 			IP_VS_DBG_RL("%s(): mtu less than 68\n", __func__);
401 			goto err_put;
402 		}
403 		maybe_update_pmtu(skb_af, skb, mtu);
404 	}
405 
406 	if (!ensure_mtu_is_adequate(ipvs, skb_af, rt_mode, ipvsh, skb, mtu))
407 		goto err_put;
408 
409 	skb_dst_drop(skb);
410 	if (noref)
411 		skb_dst_set_noref(skb, &rt->dst);
412 	else
413 		skb_dst_set(skb, &rt->dst);
414 
415 	return local;
416 
417 err_put:
418 	if (!noref)
419 		ip_rt_put(rt);
420 	return -1;
421 
422 err_unreach:
423 	dst_link_failure(skb);
424 	return -1;
425 }
426 
427 #ifdef CONFIG_IP_VS_IPV6
428 static struct dst_entry *
__ip_vs_route_output_v6(struct net * net,struct in6_addr * daddr,struct in6_addr * ret_saddr,int do_xfrm,int rt_mode)429 __ip_vs_route_output_v6(struct net *net, struct in6_addr *daddr,
430 			struct in6_addr *ret_saddr, int do_xfrm, int rt_mode)
431 {
432 	struct dst_entry *dst;
433 	struct flowi6 fl6 = {
434 		.daddr = *daddr,
435 	};
436 
437 	if (rt_mode & IP_VS_RT_MODE_KNOWN_NH)
438 		fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
439 
440 	dst = ip6_route_output(net, NULL, &fl6);
441 	if (dst->error)
442 		goto out_err;
443 	if (!ret_saddr)
444 		return dst;
445 	if (ipv6_addr_any(&fl6.saddr) &&
446 	    ipv6_dev_get_saddr(net, ip6_dst_idev(dst)->dev,
447 			       &fl6.daddr, 0, &fl6.saddr) < 0)
448 		goto out_err;
449 	if (do_xfrm) {
450 		dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
451 		if (IS_ERR(dst)) {
452 			dst = NULL;
453 			goto out_err;
454 		}
455 	}
456 	*ret_saddr = fl6.saddr;
457 	return dst;
458 
459 out_err:
460 	dst_release(dst);
461 	IP_VS_DBG_RL("ip6_route_output error, dest: %pI6\n", daddr);
462 	return NULL;
463 }
464 
465 /*
466  * Get route to destination or remote server
467  */
468 static int
__ip_vs_get_out_rt_v6(struct netns_ipvs * ipvs,int skb_af,struct sk_buff * skb,struct ip_vs_dest * dest,struct in6_addr * daddr,struct in6_addr * ret_saddr,struct ip_vs_iphdr * ipvsh,int do_xfrm,int rt_mode)469 __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int skb_af, struct sk_buff *skb,
470 		      struct ip_vs_dest *dest,
471 		      struct in6_addr *daddr, struct in6_addr *ret_saddr,
472 		      struct ip_vs_iphdr *ipvsh, int do_xfrm, int rt_mode)
473 {
474 	struct net *net = ipvs->net;
475 	struct ip_vs_dest_dst *dest_dst;
476 	struct rt6_info *rt;			/* Route to the other host */
477 	struct dst_entry *dst;
478 	int mtu;
479 	int local, noref = 1;
480 
481 	if (dest) {
482 		dest_dst = __ip_vs_dst_check(dest);
483 		if (likely(dest_dst))
484 			rt = (struct rt6_info *) dest_dst->dst_cache;
485 		else {
486 			u32 cookie;
487 
488 			dest_dst = ip_vs_dest_dst_alloc();
489 			spin_lock_bh(&dest->dst_lock);
490 			if (!dest_dst) {
491 				__ip_vs_dst_set(dest, NULL, NULL, 0);
492 				spin_unlock_bh(&dest->dst_lock);
493 				goto err_unreach;
494 			}
495 			dst = __ip_vs_route_output_v6(net, &dest->addr.in6,
496 						      &dest_dst->dst_saddr.in6,
497 						      do_xfrm, rt_mode);
498 			if (!dst) {
499 				__ip_vs_dst_set(dest, NULL, NULL, 0);
500 				spin_unlock_bh(&dest->dst_lock);
501 				ip_vs_dest_dst_free(dest_dst);
502 				goto err_unreach;
503 			}
504 			rt = (struct rt6_info *) dst;
505 			cookie = rt6_get_cookie(rt);
506 			__ip_vs_dst_set(dest, dest_dst, &rt->dst, cookie);
507 			spin_unlock_bh(&dest->dst_lock);
508 			IP_VS_DBG(10, "new dst %pI6, src %pI6, refcnt=%d\n",
509 				  &dest->addr.in6, &dest_dst->dst_saddr.in6,
510 				  atomic_read(&rt->dst.__refcnt));
511 		}
512 		if (ret_saddr)
513 			*ret_saddr = dest_dst->dst_saddr.in6;
514 	} else {
515 		noref = 0;
516 		dst = __ip_vs_route_output_v6(net, daddr, ret_saddr, do_xfrm,
517 					      rt_mode);
518 		if (!dst)
519 			goto err_unreach;
520 		rt = (struct rt6_info *) dst;
521 	}
522 
523 	local = __ip_vs_is_local_route6(rt);
524 
525 	if (unlikely(crosses_local_route_boundary(skb_af, skb, rt_mode,
526 						  local))) {
527 		IP_VS_DBG_RL("We are crossing local and non-local addresses"
528 			     " daddr=%pI6\n", daddr);
529 		goto err_put;
530 	}
531 
532 	if (unlikely(local)) {
533 		/* skb to local stack, preserve old route */
534 		if (!noref)
535 			dst_release(&rt->dst);
536 		return local;
537 	}
538 
539 	if (!decrement_ttl(ipvs, skb_af, skb))
540 		goto err_put;
541 
542 	/* MTU checking */
543 	if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL)))
544 		mtu = dst_mtu(&rt->dst);
545 	else {
546 		mtu = dst_mtu(&rt->dst) - sizeof(struct ipv6hdr);
547 		if (!dest)
548 			goto err_put;
549 		if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
550 			mtu -= sizeof(struct udphdr) + sizeof(struct guehdr);
551 			if ((dest->tun_flags &
552 			     IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
553 			    skb->ip_summed == CHECKSUM_PARTIAL)
554 				mtu -= GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
555 		} else if (dest->tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
556 			__be16 tflags = 0;
557 
558 			if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
559 				tflags |= TUNNEL_CSUM;
560 			mtu -= gre_calc_hlen(tflags);
561 		}
562 		if (mtu < IPV6_MIN_MTU) {
563 			IP_VS_DBG_RL("%s(): mtu less than %d\n", __func__,
564 				     IPV6_MIN_MTU);
565 			goto err_put;
566 		}
567 		maybe_update_pmtu(skb_af, skb, mtu);
568 	}
569 
570 	if (!ensure_mtu_is_adequate(ipvs, skb_af, rt_mode, ipvsh, skb, mtu))
571 		goto err_put;
572 
573 	skb_dst_drop(skb);
574 	if (noref)
575 		skb_dst_set_noref(skb, &rt->dst);
576 	else
577 		skb_dst_set(skb, &rt->dst);
578 
579 	return local;
580 
581 err_put:
582 	if (!noref)
583 		dst_release(&rt->dst);
584 	return -1;
585 
586 err_unreach:
587 	/* The ip6_link_failure function requires the dev field to be set
588 	 * in order to get the net (further for the sake of fwmark
589 	 * reflection).
590 	 */
591 	if (!skb->dev)
592 		skb->dev = skb_dst(skb)->dev;
593 
594 	dst_link_failure(skb);
595 	return -1;
596 }
597 #endif
598 
599 
600 /* return NF_ACCEPT to allow forwarding or other NF_xxx on error */
ip_vs_tunnel_xmit_prepare(struct sk_buff * skb,struct ip_vs_conn * cp)601 static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff *skb,
602 					    struct ip_vs_conn *cp)
603 {
604 	int ret = NF_ACCEPT;
605 
606 	skb->ipvs_property = 1;
607 	if (unlikely(cp->flags & IP_VS_CONN_F_NFCT))
608 		ret = ip_vs_confirm_conntrack(skb);
609 	if (ret == NF_ACCEPT) {
610 		nf_reset_ct(skb);
611 		skb_forward_csum(skb);
612 		if (skb->dev)
613 			skb_clear_tstamp(skb);
614 	}
615 	return ret;
616 }
617 
618 /* In the event of a remote destination, it's possible that we would have
619  * matches against an old socket (particularly a TIME-WAIT socket). This
620  * causes havoc down the line (ip_local_out et. al. expect regular sockets
621  * and invalid memory accesses will happen) so simply drop the association
622  * in this case.
623 */
ip_vs_drop_early_demux_sk(struct sk_buff * skb)624 static inline void ip_vs_drop_early_demux_sk(struct sk_buff *skb)
625 {
626 	/* If dev is set, the packet came from the LOCAL_IN callback and
627 	 * not from a local TCP socket.
628 	 */
629 	if (skb->dev)
630 		skb_orphan(skb);
631 }
632 
633 /* return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) */
ip_vs_nat_send_or_cont(int pf,struct sk_buff * skb,struct ip_vs_conn * cp,int local)634 static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff *skb,
635 					 struct ip_vs_conn *cp, int local)
636 {
637 	int ret = NF_STOLEN;
638 
639 	skb->ipvs_property = 1;
640 	if (likely(!(cp->flags & IP_VS_CONN_F_NFCT)))
641 		ip_vs_notrack(skb);
642 	else
643 		ip_vs_update_conntrack(skb, cp, 1);
644 
645 	/* Remove the early_demux association unless it's bound for the
646 	 * exact same port and address on this host after translation.
647 	 */
648 	if (!local || cp->vport != cp->dport ||
649 	    !ip_vs_addr_equal(cp->af, &cp->vaddr, &cp->daddr))
650 		ip_vs_drop_early_demux_sk(skb);
651 
652 	if (!local) {
653 		skb_forward_csum(skb);
654 		if (skb->dev)
655 			skb_clear_tstamp(skb);
656 		NF_HOOK(pf, NF_INET_LOCAL_OUT, cp->ipvs->net, NULL, skb,
657 			NULL, skb_dst(skb)->dev, dst_output);
658 	} else
659 		ret = NF_ACCEPT;
660 
661 	return ret;
662 }
663 
664 /* return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) */
ip_vs_send_or_cont(int pf,struct sk_buff * skb,struct ip_vs_conn * cp,int local)665 static inline int ip_vs_send_or_cont(int pf, struct sk_buff *skb,
666 				     struct ip_vs_conn *cp, int local)
667 {
668 	int ret = NF_STOLEN;
669 
670 	skb->ipvs_property = 1;
671 	if (likely(!(cp->flags & IP_VS_CONN_F_NFCT)))
672 		ip_vs_notrack(skb);
673 	if (!local) {
674 		ip_vs_drop_early_demux_sk(skb);
675 		skb_forward_csum(skb);
676 		if (skb->dev)
677 			skb_clear_tstamp(skb);
678 		NF_HOOK(pf, NF_INET_LOCAL_OUT, cp->ipvs->net, NULL, skb,
679 			NULL, skb_dst(skb)->dev, dst_output);
680 	} else
681 		ret = NF_ACCEPT;
682 	return ret;
683 }
684 
685 
686 /*
687  *      NULL transmitter (do nothing except return NF_ACCEPT)
688  */
689 int
ip_vs_null_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)690 ip_vs_null_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
691 		struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
692 {
693 	/* we do not touch skb and do not need pskb ptr */
694 	return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
695 }
696 
697 
698 /*
699  *      Bypass transmitter
700  *      Let packets bypass the destination when the destination is not
701  *      available, it may be only used in transparent cache cluster.
702  */
703 int
ip_vs_bypass_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)704 ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
705 		  struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
706 {
707 	struct iphdr  *iph = ip_hdr(skb);
708 
709 	EnterFunction(10);
710 
711 	if (__ip_vs_get_out_rt(cp->ipvs, cp->af, skb, NULL, iph->daddr,
712 			       IP_VS_RT_MODE_NON_LOCAL, NULL, ipvsh) < 0)
713 		goto tx_error;
714 
715 	ip_send_check(iph);
716 
717 	/* Another hack: avoid icmp_send in ip_fragment */
718 	skb->ignore_df = 1;
719 
720 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
721 
722 	LeaveFunction(10);
723 	return NF_STOLEN;
724 
725  tx_error:
726 	kfree_skb(skb);
727 	LeaveFunction(10);
728 	return NF_STOLEN;
729 }
730 
731 #ifdef CONFIG_IP_VS_IPV6
732 int
ip_vs_bypass_xmit_v6(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)733 ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
734 		     struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
735 {
736 	struct ipv6hdr *iph = ipv6_hdr(skb);
737 
738 	EnterFunction(10);
739 
740 	if (__ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, NULL,
741 				  &iph->daddr, NULL,
742 				  ipvsh, 0, IP_VS_RT_MODE_NON_LOCAL) < 0)
743 		goto tx_error;
744 
745 	/* Another hack: avoid icmp_send in ip_fragment */
746 	skb->ignore_df = 1;
747 
748 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
749 
750 	LeaveFunction(10);
751 	return NF_STOLEN;
752 
753  tx_error:
754 	kfree_skb(skb);
755 	LeaveFunction(10);
756 	return NF_STOLEN;
757 }
758 #endif
759 
760 /*
761  *      NAT transmitter (only for outside-to-inside nat forwarding)
762  *      Not used for related ICMP
763  */
764 int
ip_vs_nat_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)765 ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
766 	       struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
767 {
768 	struct rtable *rt;		/* Route to the other host */
769 	int local, rc, was_input;
770 
771 	EnterFunction(10);
772 
773 	/* check if it is a connection of no-client-port */
774 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
775 		__be16 _pt, *p;
776 
777 		p = skb_header_pointer(skb, ipvsh->len, sizeof(_pt), &_pt);
778 		if (p == NULL)
779 			goto tx_error;
780 		ip_vs_conn_fill_cport(cp, *p);
781 		IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
782 	}
783 
784 	was_input = rt_is_input_route(skb_rtable(skb));
785 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
786 				   IP_VS_RT_MODE_LOCAL |
787 				   IP_VS_RT_MODE_NON_LOCAL |
788 				   IP_VS_RT_MODE_RDR, NULL, ipvsh);
789 	if (local < 0)
790 		goto tx_error;
791 	rt = skb_rtable(skb);
792 	/*
793 	 * Avoid duplicate tuple in reply direction for NAT traffic
794 	 * to local address when connection is sync-ed
795 	 */
796 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
797 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
798 		enum ip_conntrack_info ctinfo;
799 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
800 
801 		if (ct) {
802 			IP_VS_DBG_RL_PKT(10, AF_INET, pp, skb, ipvsh->off,
803 					 "ip_vs_nat_xmit(): "
804 					 "stopping DNAT to local address");
805 			goto tx_error;
806 		}
807 	}
808 #endif
809 
810 	/* From world but DNAT to loopback address? */
811 	if (local && ipv4_is_loopback(cp->daddr.ip) && was_input) {
812 		IP_VS_DBG_RL_PKT(1, AF_INET, pp, skb, ipvsh->off,
813 				 "ip_vs_nat_xmit(): stopping DNAT to loopback "
814 				 "address");
815 		goto tx_error;
816 	}
817 
818 	/* copy-on-write the packet before mangling it */
819 	if (skb_ensure_writable(skb, sizeof(struct iphdr)))
820 		goto tx_error;
821 
822 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
823 		goto tx_error;
824 
825 	/* mangle the packet */
826 	if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp, ipvsh))
827 		goto tx_error;
828 	ip_hdr(skb)->daddr = cp->daddr.ip;
829 	ip_send_check(ip_hdr(skb));
830 
831 	IP_VS_DBG_PKT(10, AF_INET, pp, skb, ipvsh->off, "After DNAT");
832 
833 	/* FIXME: when application helper enlarges the packet and the length
834 	   is larger than the MTU of outgoing device, there will be still
835 	   MTU problem. */
836 
837 	/* Another hack: avoid icmp_send in ip_fragment */
838 	skb->ignore_df = 1;
839 
840 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
841 
842 	LeaveFunction(10);
843 	return rc;
844 
845   tx_error:
846 	kfree_skb(skb);
847 	LeaveFunction(10);
848 	return NF_STOLEN;
849 }
850 
851 #ifdef CONFIG_IP_VS_IPV6
852 int
ip_vs_nat_xmit_v6(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)853 ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
854 		  struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
855 {
856 	struct rt6_info *rt;		/* Route to the other host */
857 	int local, rc;
858 
859 	EnterFunction(10);
860 
861 	/* check if it is a connection of no-client-port */
862 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT && !ipvsh->fragoffs)) {
863 		__be16 _pt, *p;
864 		p = skb_header_pointer(skb, ipvsh->len, sizeof(_pt), &_pt);
865 		if (p == NULL)
866 			goto tx_error;
867 		ip_vs_conn_fill_cport(cp, *p);
868 		IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
869 	}
870 
871 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
872 				      &cp->daddr.in6,
873 				      NULL, ipvsh, 0,
874 				      IP_VS_RT_MODE_LOCAL |
875 				      IP_VS_RT_MODE_NON_LOCAL |
876 				      IP_VS_RT_MODE_RDR);
877 	if (local < 0)
878 		goto tx_error;
879 	rt = (struct rt6_info *) skb_dst(skb);
880 	/*
881 	 * Avoid duplicate tuple in reply direction for NAT traffic
882 	 * to local address when connection is sync-ed
883 	 */
884 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
885 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
886 		enum ip_conntrack_info ctinfo;
887 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
888 
889 		if (ct) {
890 			IP_VS_DBG_RL_PKT(10, AF_INET6, pp, skb, ipvsh->off,
891 					 "ip_vs_nat_xmit_v6(): "
892 					 "stopping DNAT to local address");
893 			goto tx_error;
894 		}
895 	}
896 #endif
897 
898 	/* From world but DNAT to loopback address? */
899 	if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
900 	    ipv6_addr_type(&cp->daddr.in6) & IPV6_ADDR_LOOPBACK) {
901 		IP_VS_DBG_RL_PKT(1, AF_INET6, pp, skb, ipvsh->off,
902 				 "ip_vs_nat_xmit_v6(): "
903 				 "stopping DNAT to loopback address");
904 		goto tx_error;
905 	}
906 
907 	/* copy-on-write the packet before mangling it */
908 	if (skb_ensure_writable(skb, sizeof(struct ipv6hdr)))
909 		goto tx_error;
910 
911 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
912 		goto tx_error;
913 
914 	/* mangle the packet */
915 	if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp, ipvsh))
916 		goto tx_error;
917 	ipv6_hdr(skb)->daddr = cp->daddr.in6;
918 
919 	IP_VS_DBG_PKT(10, AF_INET6, pp, skb, ipvsh->off, "After DNAT");
920 
921 	/* FIXME: when application helper enlarges the packet and the length
922 	   is larger than the MTU of outgoing device, there will be still
923 	   MTU problem. */
924 
925 	/* Another hack: avoid icmp_send in ip_fragment */
926 	skb->ignore_df = 1;
927 
928 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
929 
930 	LeaveFunction(10);
931 	return rc;
932 
933 tx_error:
934 	LeaveFunction(10);
935 	kfree_skb(skb);
936 	return NF_STOLEN;
937 }
938 #endif
939 
940 /* When forwarding a packet, we must ensure that we've got enough headroom
941  * for the encapsulation packet in the skb.  This also gives us an
942  * opportunity to figure out what the payload_len, dsfield, ttl, and df
943  * values should be, so that we won't need to look at the old ip header
944  * again
945  */
946 static struct sk_buff *
ip_vs_prepare_tunneled_skb(struct sk_buff * skb,int skb_af,unsigned int max_headroom,__u8 * next_protocol,__u32 * payload_len,__u8 * dsfield,__u8 * ttl,__be16 * df)947 ip_vs_prepare_tunneled_skb(struct sk_buff *skb, int skb_af,
948 			   unsigned int max_headroom, __u8 *next_protocol,
949 			   __u32 *payload_len, __u8 *dsfield, __u8 *ttl,
950 			   __be16 *df)
951 {
952 	struct sk_buff *new_skb = NULL;
953 	struct iphdr *old_iph = NULL;
954 	__u8 old_dsfield;
955 #ifdef CONFIG_IP_VS_IPV6
956 	struct ipv6hdr *old_ipv6h = NULL;
957 #endif
958 
959 	ip_vs_drop_early_demux_sk(skb);
960 
961 	if (skb_headroom(skb) < max_headroom || skb_cloned(skb)) {
962 		new_skb = skb_realloc_headroom(skb, max_headroom);
963 		if (!new_skb)
964 			goto error;
965 		if (skb->sk)
966 			skb_set_owner_w(new_skb, skb->sk);
967 		consume_skb(skb);
968 		skb = new_skb;
969 	}
970 
971 #ifdef CONFIG_IP_VS_IPV6
972 	if (skb_af == AF_INET6) {
973 		old_ipv6h = ipv6_hdr(skb);
974 		*next_protocol = IPPROTO_IPV6;
975 		if (payload_len)
976 			*payload_len =
977 				ntohs(old_ipv6h->payload_len) +
978 				sizeof(*old_ipv6h);
979 		old_dsfield = ipv6_get_dsfield(old_ipv6h);
980 		*ttl = old_ipv6h->hop_limit;
981 		if (df)
982 			*df = 0;
983 	} else
984 #endif
985 	{
986 		old_iph = ip_hdr(skb);
987 		/* Copy DF, reset fragment offset and MF */
988 		if (df)
989 			*df = (old_iph->frag_off & htons(IP_DF));
990 		*next_protocol = IPPROTO_IPIP;
991 
992 		/* fix old IP header checksum */
993 		ip_send_check(old_iph);
994 		old_dsfield = ipv4_get_dsfield(old_iph);
995 		*ttl = old_iph->ttl;
996 		if (payload_len)
997 			*payload_len = ntohs(old_iph->tot_len);
998 	}
999 
1000 	/* Implement full-functionality option for ECN encapsulation */
1001 	*dsfield = INET_ECN_encapsulate(old_dsfield, old_dsfield);
1002 
1003 	return skb;
1004 error:
1005 	kfree_skb(skb);
1006 	return ERR_PTR(-ENOMEM);
1007 }
1008 
__tun_gso_type_mask(int encaps_af,int orig_af)1009 static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
1010 {
1011 	switch (encaps_af) {
1012 	case AF_INET:
1013 		return SKB_GSO_IPXIP4;
1014 	case AF_INET6:
1015 		return SKB_GSO_IPXIP6;
1016 	default:
1017 		return 0;
1018 	}
1019 }
1020 
1021 static int
ipvs_gue_encap(struct net * net,struct sk_buff * skb,struct ip_vs_conn * cp,__u8 * next_protocol)1022 ipvs_gue_encap(struct net *net, struct sk_buff *skb,
1023 	       struct ip_vs_conn *cp, __u8 *next_protocol)
1024 {
1025 	__be16 dport;
1026 	__be16 sport = udp_flow_src_port(net, skb, 0, 0, false);
1027 	struct udphdr  *udph;	/* Our new UDP header */
1028 	struct guehdr  *gueh;	/* Our new GUE header */
1029 	size_t hdrlen, optlen = 0;
1030 	void *data;
1031 	bool need_priv = false;
1032 
1033 	if ((cp->dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1034 	    skb->ip_summed == CHECKSUM_PARTIAL) {
1035 		optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1036 		need_priv = true;
1037 	}
1038 
1039 	hdrlen = sizeof(struct guehdr) + optlen;
1040 
1041 	skb_push(skb, hdrlen);
1042 
1043 	gueh = (struct guehdr *)skb->data;
1044 
1045 	gueh->control = 0;
1046 	gueh->version = 0;
1047 	gueh->hlen = optlen >> 2;
1048 	gueh->flags = 0;
1049 	gueh->proto_ctype = *next_protocol;
1050 
1051 	data = &gueh[1];
1052 
1053 	if (need_priv) {
1054 		__be32 *flags = data;
1055 		u16 csum_start = skb_checksum_start_offset(skb);
1056 		__be16 *pd;
1057 
1058 		gueh->flags |= GUE_FLAG_PRIV;
1059 		*flags = 0;
1060 		data += GUE_LEN_PRIV;
1061 
1062 		if (csum_start < hdrlen)
1063 			return -EINVAL;
1064 
1065 		csum_start -= hdrlen;
1066 		pd = data;
1067 		pd[0] = htons(csum_start);
1068 		pd[1] = htons(csum_start + skb->csum_offset);
1069 
1070 		if (!skb_is_gso(skb)) {
1071 			skb->ip_summed = CHECKSUM_NONE;
1072 			skb->encapsulation = 0;
1073 		}
1074 
1075 		*flags |= GUE_PFLAG_REMCSUM;
1076 		data += GUE_PLEN_REMCSUM;
1077 	}
1078 
1079 	skb_push(skb, sizeof(struct udphdr));
1080 	skb_reset_transport_header(skb);
1081 
1082 	udph = udp_hdr(skb);
1083 
1084 	dport = cp->dest->tun_port;
1085 	udph->dest = dport;
1086 	udph->source = sport;
1087 	udph->len = htons(skb->len);
1088 	udph->check = 0;
1089 
1090 	*next_protocol = IPPROTO_UDP;
1091 
1092 	return 0;
1093 }
1094 
1095 static void
ipvs_gre_encap(struct net * net,struct sk_buff * skb,struct ip_vs_conn * cp,__u8 * next_protocol)1096 ipvs_gre_encap(struct net *net, struct sk_buff *skb,
1097 	       struct ip_vs_conn *cp, __u8 *next_protocol)
1098 {
1099 	__be16 proto = *next_protocol == IPPROTO_IPIP ?
1100 				htons(ETH_P_IP) : htons(ETH_P_IPV6);
1101 	__be16 tflags = 0;
1102 	size_t hdrlen;
1103 
1104 	if (cp->dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1105 		tflags |= TUNNEL_CSUM;
1106 
1107 	hdrlen = gre_calc_hlen(tflags);
1108 	gre_build_header(skb, hdrlen, tflags, proto, 0, 0);
1109 
1110 	*next_protocol = IPPROTO_GRE;
1111 }
1112 
1113 /*
1114  *   IP Tunneling transmitter
1115  *
1116  *   This function encapsulates the packet in a new IP packet, its
1117  *   destination will be set to cp->daddr. Most code of this function
1118  *   is taken from ipip.c.
1119  *
1120  *   It is used in VS/TUN cluster. The load balancer selects a real
1121  *   server from a cluster based on a scheduling algorithm,
1122  *   encapsulates the request packet and forwards it to the selected
1123  *   server. For example, all real servers are configured with
1124  *   "ifconfig tunl0 <Virtual IP Address> up". When the server receives
1125  *   the encapsulated packet, it will decapsulate the packet, processe
1126  *   the request and return the response packets directly to the client
1127  *   without passing the load balancer. This can greatly increase the
1128  *   scalability of virtual server.
1129  *
1130  *   Used for ANY protocol
1131  */
1132 int
ip_vs_tunnel_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1133 ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1134 		  struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1135 {
1136 	struct netns_ipvs *ipvs = cp->ipvs;
1137 	struct net *net = ipvs->net;
1138 	struct rtable *rt;			/* Route to the other host */
1139 	__be32 saddr;				/* Source for tunnel */
1140 	struct net_device *tdev;		/* Device to other host */
1141 	__u8 next_protocol = 0;
1142 	__u8 dsfield = 0;
1143 	__u8 ttl = 0;
1144 	__be16 df = 0;
1145 	__be16 *dfp = NULL;
1146 	struct iphdr  *iph;			/* Our new IP header */
1147 	unsigned int max_headroom;		/* The extra header space needed */
1148 	int ret, local;
1149 	int tun_type, gso_type;
1150 	int tun_flags;
1151 
1152 	EnterFunction(10);
1153 
1154 	local = __ip_vs_get_out_rt(ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
1155 				   IP_VS_RT_MODE_LOCAL |
1156 				   IP_VS_RT_MODE_NON_LOCAL |
1157 				   IP_VS_RT_MODE_CONNECT |
1158 				   IP_VS_RT_MODE_TUNNEL, &saddr, ipvsh);
1159 	if (local < 0)
1160 		goto tx_error;
1161 	if (local)
1162 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
1163 
1164 	rt = skb_rtable(skb);
1165 	tdev = rt->dst.dev;
1166 
1167 	/*
1168 	 * Okay, now see if we can stuff it in the buffer as-is.
1169 	 */
1170 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
1171 
1172 	tun_type = cp->dest->tun_type;
1173 	tun_flags = cp->dest->tun_flags;
1174 
1175 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1176 		size_t gue_hdrlen, gue_optlen = 0;
1177 
1178 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1179 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1180 			gue_optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1181 		}
1182 		gue_hdrlen = sizeof(struct guehdr) + gue_optlen;
1183 
1184 		max_headroom += sizeof(struct udphdr) + gue_hdrlen;
1185 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1186 		size_t gre_hdrlen;
1187 		__be16 tflags = 0;
1188 
1189 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1190 			tflags |= TUNNEL_CSUM;
1191 		gre_hdrlen = gre_calc_hlen(tflags);
1192 
1193 		max_headroom += gre_hdrlen;
1194 	}
1195 
1196 	/* We only care about the df field if sysctl_pmtu_disc(ipvs) is set */
1197 	dfp = sysctl_pmtu_disc(ipvs) ? &df : NULL;
1198 	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
1199 					 &next_protocol, NULL, &dsfield,
1200 					 &ttl, dfp);
1201 	if (IS_ERR(skb))
1202 		goto tx_error;
1203 
1204 	gso_type = __tun_gso_type_mask(AF_INET, cp->af);
1205 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1206 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1207 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1208 			gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
1209 		else
1210 			gso_type |= SKB_GSO_UDP_TUNNEL;
1211 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1212 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1213 			gso_type |= SKB_GSO_TUNNEL_REMCSUM;
1214 		}
1215 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1216 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1217 			gso_type |= SKB_GSO_GRE_CSUM;
1218 		else
1219 			gso_type |= SKB_GSO_GRE;
1220 	}
1221 
1222 	if (iptunnel_handle_offloads(skb, gso_type))
1223 		goto tx_error;
1224 
1225 	skb->transport_header = skb->network_header;
1226 
1227 	skb_set_inner_ipproto(skb, next_protocol);
1228 
1229 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1230 		bool check = false;
1231 
1232 		if (ipvs_gue_encap(net, skb, cp, &next_protocol))
1233 			goto tx_error;
1234 
1235 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1236 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1237 			check = true;
1238 
1239 		udp_set_csum(!check, skb, saddr, cp->daddr.ip, skb->len);
1240 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE)
1241 		ipvs_gre_encap(net, skb, cp, &next_protocol);
1242 
1243 	skb_push(skb, sizeof(struct iphdr));
1244 	skb_reset_network_header(skb);
1245 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1246 
1247 	/*
1248 	 *	Push down and install the IPIP header.
1249 	 */
1250 	iph			=	ip_hdr(skb);
1251 	iph->version		=	4;
1252 	iph->ihl		=	sizeof(struct iphdr)>>2;
1253 	iph->frag_off		=	df;
1254 	iph->protocol		=	next_protocol;
1255 	iph->tos		=	dsfield;
1256 	iph->daddr		=	cp->daddr.ip;
1257 	iph->saddr		=	saddr;
1258 	iph->ttl		=	ttl;
1259 	ip_select_ident(net, skb, NULL);
1260 
1261 	/* Another hack: avoid icmp_send in ip_fragment */
1262 	skb->ignore_df = 1;
1263 
1264 	ret = ip_vs_tunnel_xmit_prepare(skb, cp);
1265 	if (ret == NF_ACCEPT)
1266 		ip_local_out(net, skb->sk, skb);
1267 	else if (ret == NF_DROP)
1268 		kfree_skb(skb);
1269 
1270 	LeaveFunction(10);
1271 
1272 	return NF_STOLEN;
1273 
1274   tx_error:
1275 	if (!IS_ERR(skb))
1276 		kfree_skb(skb);
1277 	LeaveFunction(10);
1278 	return NF_STOLEN;
1279 }
1280 
1281 #ifdef CONFIG_IP_VS_IPV6
1282 int
ip_vs_tunnel_xmit_v6(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1283 ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1284 		     struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1285 {
1286 	struct netns_ipvs *ipvs = cp->ipvs;
1287 	struct net *net = ipvs->net;
1288 	struct rt6_info *rt;		/* Route to the other host */
1289 	struct in6_addr saddr;		/* Source for tunnel */
1290 	struct net_device *tdev;	/* Device to other host */
1291 	__u8 next_protocol = 0;
1292 	__u32 payload_len = 0;
1293 	__u8 dsfield = 0;
1294 	__u8 ttl = 0;
1295 	struct ipv6hdr  *iph;		/* Our new IP header */
1296 	unsigned int max_headroom;	/* The extra header space needed */
1297 	int ret, local;
1298 	int tun_type, gso_type;
1299 	int tun_flags;
1300 
1301 	EnterFunction(10);
1302 
1303 	local = __ip_vs_get_out_rt_v6(ipvs, cp->af, skb, cp->dest,
1304 				      &cp->daddr.in6,
1305 				      &saddr, ipvsh, 1,
1306 				      IP_VS_RT_MODE_LOCAL |
1307 				      IP_VS_RT_MODE_NON_LOCAL |
1308 				      IP_VS_RT_MODE_TUNNEL);
1309 	if (local < 0)
1310 		goto tx_error;
1311 	if (local)
1312 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
1313 
1314 	rt = (struct rt6_info *) skb_dst(skb);
1315 	tdev = rt->dst.dev;
1316 
1317 	/*
1318 	 * Okay, now see if we can stuff it in the buffer as-is.
1319 	 */
1320 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct ipv6hdr);
1321 
1322 	tun_type = cp->dest->tun_type;
1323 	tun_flags = cp->dest->tun_flags;
1324 
1325 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1326 		size_t gue_hdrlen, gue_optlen = 0;
1327 
1328 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1329 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1330 			gue_optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1331 		}
1332 		gue_hdrlen = sizeof(struct guehdr) + gue_optlen;
1333 
1334 		max_headroom += sizeof(struct udphdr) + gue_hdrlen;
1335 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1336 		size_t gre_hdrlen;
1337 		__be16 tflags = 0;
1338 
1339 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1340 			tflags |= TUNNEL_CSUM;
1341 		gre_hdrlen = gre_calc_hlen(tflags);
1342 
1343 		max_headroom += gre_hdrlen;
1344 	}
1345 
1346 	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
1347 					 &next_protocol, &payload_len,
1348 					 &dsfield, &ttl, NULL);
1349 	if (IS_ERR(skb))
1350 		goto tx_error;
1351 
1352 	gso_type = __tun_gso_type_mask(AF_INET6, cp->af);
1353 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1354 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1355 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1356 			gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
1357 		else
1358 			gso_type |= SKB_GSO_UDP_TUNNEL;
1359 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1360 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1361 			gso_type |= SKB_GSO_TUNNEL_REMCSUM;
1362 		}
1363 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1364 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1365 			gso_type |= SKB_GSO_GRE_CSUM;
1366 		else
1367 			gso_type |= SKB_GSO_GRE;
1368 	}
1369 
1370 	if (iptunnel_handle_offloads(skb, gso_type))
1371 		goto tx_error;
1372 
1373 	skb->transport_header = skb->network_header;
1374 
1375 	skb_set_inner_ipproto(skb, next_protocol);
1376 
1377 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1378 		bool check = false;
1379 
1380 		if (ipvs_gue_encap(net, skb, cp, &next_protocol))
1381 			goto tx_error;
1382 
1383 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1384 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1385 			check = true;
1386 
1387 		udp6_set_csum(!check, skb, &saddr, &cp->daddr.in6, skb->len);
1388 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE)
1389 		ipvs_gre_encap(net, skb, cp, &next_protocol);
1390 
1391 	skb_push(skb, sizeof(struct ipv6hdr));
1392 	skb_reset_network_header(skb);
1393 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1394 
1395 	/*
1396 	 *	Push down and install the IPIP header.
1397 	 */
1398 	iph			=	ipv6_hdr(skb);
1399 	iph->version		=	6;
1400 	iph->nexthdr		=	next_protocol;
1401 	iph->payload_len	=	htons(payload_len);
1402 	memset(&iph->flow_lbl, 0, sizeof(iph->flow_lbl));
1403 	ipv6_change_dsfield(iph, 0, dsfield);
1404 	iph->daddr = cp->daddr.in6;
1405 	iph->saddr = saddr;
1406 	iph->hop_limit		=	ttl;
1407 
1408 	/* Another hack: avoid icmp_send in ip_fragment */
1409 	skb->ignore_df = 1;
1410 
1411 	ret = ip_vs_tunnel_xmit_prepare(skb, cp);
1412 	if (ret == NF_ACCEPT)
1413 		ip6_local_out(net, skb->sk, skb);
1414 	else if (ret == NF_DROP)
1415 		kfree_skb(skb);
1416 
1417 	LeaveFunction(10);
1418 
1419 	return NF_STOLEN;
1420 
1421 tx_error:
1422 	if (!IS_ERR(skb))
1423 		kfree_skb(skb);
1424 	LeaveFunction(10);
1425 	return NF_STOLEN;
1426 }
1427 #endif
1428 
1429 
1430 /*
1431  *      Direct Routing transmitter
1432  *      Used for ANY protocol
1433  */
1434 int
ip_vs_dr_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1435 ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1436 	      struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1437 {
1438 	int local;
1439 
1440 	EnterFunction(10);
1441 
1442 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
1443 				   IP_VS_RT_MODE_LOCAL |
1444 				   IP_VS_RT_MODE_NON_LOCAL |
1445 				   IP_VS_RT_MODE_KNOWN_NH, NULL, ipvsh);
1446 	if (local < 0)
1447 		goto tx_error;
1448 	if (local)
1449 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
1450 
1451 	ip_send_check(ip_hdr(skb));
1452 
1453 	/* Another hack: avoid icmp_send in ip_fragment */
1454 	skb->ignore_df = 1;
1455 
1456 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
1457 
1458 	LeaveFunction(10);
1459 	return NF_STOLEN;
1460 
1461   tx_error:
1462 	kfree_skb(skb);
1463 	LeaveFunction(10);
1464 	return NF_STOLEN;
1465 }
1466 
1467 #ifdef CONFIG_IP_VS_IPV6
1468 int
ip_vs_dr_xmit_v6(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1469 ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1470 		 struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1471 {
1472 	int local;
1473 
1474 	EnterFunction(10);
1475 
1476 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
1477 				      &cp->daddr.in6,
1478 				      NULL, ipvsh, 0,
1479 				      IP_VS_RT_MODE_LOCAL |
1480 				      IP_VS_RT_MODE_NON_LOCAL |
1481 				      IP_VS_RT_MODE_KNOWN_NH);
1482 	if (local < 0)
1483 		goto tx_error;
1484 	if (local)
1485 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
1486 
1487 	/* Another hack: avoid icmp_send in ip_fragment */
1488 	skb->ignore_df = 1;
1489 
1490 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
1491 
1492 	LeaveFunction(10);
1493 	return NF_STOLEN;
1494 
1495 tx_error:
1496 	kfree_skb(skb);
1497 	LeaveFunction(10);
1498 	return NF_STOLEN;
1499 }
1500 #endif
1501 
1502 
1503 /*
1504  *	ICMP packet transmitter
1505  *	called by the ip_vs_in_icmp
1506  */
1507 int
ip_vs_icmp_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,int offset,unsigned int hooknum,struct ip_vs_iphdr * iph)1508 ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1509 		struct ip_vs_protocol *pp, int offset, unsigned int hooknum,
1510 		struct ip_vs_iphdr *iph)
1511 {
1512 	struct rtable	*rt;	/* Route to the other host */
1513 	int rc;
1514 	int local;
1515 	int rt_mode, was_input;
1516 
1517 	EnterFunction(10);
1518 
1519 	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
1520 	   forwarded directly here, because there is no need to
1521 	   translate address/port back */
1522 	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
1523 		if (cp->packet_xmit)
1524 			rc = cp->packet_xmit(skb, cp, pp, iph);
1525 		else
1526 			rc = NF_ACCEPT;
1527 		/* do not touch skb anymore */
1528 		atomic_inc(&cp->in_pkts);
1529 		goto out;
1530 	}
1531 
1532 	/*
1533 	 * mangle and send the packet here (only for VS/NAT)
1534 	 */
1535 	was_input = rt_is_input_route(skb_rtable(skb));
1536 
1537 	/* LOCALNODE from FORWARD hook is not supported */
1538 	rt_mode = (hooknum != NF_INET_FORWARD) ?
1539 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
1540 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
1541 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip, rt_mode,
1542 				   NULL, iph);
1543 	if (local < 0)
1544 		goto tx_error;
1545 	rt = skb_rtable(skb);
1546 
1547 	/*
1548 	 * Avoid duplicate tuple in reply direction for NAT traffic
1549 	 * to local address when connection is sync-ed
1550 	 */
1551 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
1552 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
1553 		enum ip_conntrack_info ctinfo;
1554 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1555 
1556 		if (ct) {
1557 			IP_VS_DBG(10, "%s(): "
1558 				  "stopping DNAT to local address %pI4\n",
1559 				  __func__, &cp->daddr.ip);
1560 			goto tx_error;
1561 		}
1562 	}
1563 #endif
1564 
1565 	/* From world but DNAT to loopback address? */
1566 	if (local && ipv4_is_loopback(cp->daddr.ip) && was_input) {
1567 		IP_VS_DBG(1, "%s(): "
1568 			  "stopping DNAT to loopback %pI4\n",
1569 			  __func__, &cp->daddr.ip);
1570 		goto tx_error;
1571 	}
1572 
1573 	/* copy-on-write the packet before mangling it */
1574 	if (skb_ensure_writable(skb, offset))
1575 		goto tx_error;
1576 
1577 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
1578 		goto tx_error;
1579 
1580 	ip_vs_nat_icmp(skb, pp, cp, 0);
1581 
1582 	/* Another hack: avoid icmp_send in ip_fragment */
1583 	skb->ignore_df = 1;
1584 
1585 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
1586 	goto out;
1587 
1588   tx_error:
1589 	kfree_skb(skb);
1590 	rc = NF_STOLEN;
1591   out:
1592 	LeaveFunction(10);
1593 	return rc;
1594 }
1595 
1596 #ifdef CONFIG_IP_VS_IPV6
1597 int
ip_vs_icmp_xmit_v6(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,int offset,unsigned int hooknum,struct ip_vs_iphdr * ipvsh)1598 ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1599 		struct ip_vs_protocol *pp, int offset, unsigned int hooknum,
1600 		struct ip_vs_iphdr *ipvsh)
1601 {
1602 	struct rt6_info	*rt;	/* Route to the other host */
1603 	int rc;
1604 	int local;
1605 	int rt_mode;
1606 
1607 	EnterFunction(10);
1608 
1609 	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
1610 	   forwarded directly here, because there is no need to
1611 	   translate address/port back */
1612 	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
1613 		if (cp->packet_xmit)
1614 			rc = cp->packet_xmit(skb, cp, pp, ipvsh);
1615 		else
1616 			rc = NF_ACCEPT;
1617 		/* do not touch skb anymore */
1618 		atomic_inc(&cp->in_pkts);
1619 		goto out;
1620 	}
1621 
1622 	/*
1623 	 * mangle and send the packet here (only for VS/NAT)
1624 	 */
1625 
1626 	/* LOCALNODE from FORWARD hook is not supported */
1627 	rt_mode = (hooknum != NF_INET_FORWARD) ?
1628 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
1629 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
1630 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
1631 				      &cp->daddr.in6, NULL, ipvsh, 0, rt_mode);
1632 	if (local < 0)
1633 		goto tx_error;
1634 	rt = (struct rt6_info *) skb_dst(skb);
1635 	/*
1636 	 * Avoid duplicate tuple in reply direction for NAT traffic
1637 	 * to local address when connection is sync-ed
1638 	 */
1639 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
1640 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
1641 		enum ip_conntrack_info ctinfo;
1642 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1643 
1644 		if (ct) {
1645 			IP_VS_DBG(10, "%s(): "
1646 				  "stopping DNAT to local address %pI6\n",
1647 				  __func__, &cp->daddr.in6);
1648 			goto tx_error;
1649 		}
1650 	}
1651 #endif
1652 
1653 	/* From world but DNAT to loopback address? */
1654 	if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
1655 	    ipv6_addr_type(&cp->daddr.in6) & IPV6_ADDR_LOOPBACK) {
1656 		IP_VS_DBG(1, "%s(): "
1657 			  "stopping DNAT to loopback %pI6\n",
1658 			  __func__, &cp->daddr.in6);
1659 		goto tx_error;
1660 	}
1661 
1662 	/* copy-on-write the packet before mangling it */
1663 	if (skb_ensure_writable(skb, offset))
1664 		goto tx_error;
1665 
1666 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
1667 		goto tx_error;
1668 
1669 	ip_vs_nat_icmp_v6(skb, pp, cp, 0);
1670 
1671 	/* Another hack: avoid icmp_send in ip_fragment */
1672 	skb->ignore_df = 1;
1673 
1674 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
1675 	goto out;
1676 
1677 tx_error:
1678 	kfree_skb(skb);
1679 	rc = NF_STOLEN;
1680 out:
1681 	LeaveFunction(10);
1682 	return rc;
1683 }
1684 #endif
1685