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, 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, 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 			dst_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 = dst_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 				  rcuref_read(&rt->dst.__rcuref));
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 			IP_TUNNEL_DECLARE_FLAGS(tflags) = { };
394 
395 			if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
396 				__set_bit(IP_TUNNEL_CSUM_BIT, tflags);
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 = dst_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 = dst_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 				  rcuref_read(&rt->dst.__rcuref));
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 = dst_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 			IP_TUNNEL_DECLARE_FLAGS(tflags) = { };
557 
558 			if (dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
559 				__set_bit(IP_TUNNEL_CSUM_BIT, tflags);
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 	if (__ip_vs_get_out_rt(cp->ipvs, cp->af, skb, NULL, iph->daddr,
710 			       IP_VS_RT_MODE_NON_LOCAL, NULL, ipvsh) < 0)
711 		goto tx_error;
712 
713 	ip_send_check(iph);
714 
715 	/* Another hack: avoid icmp_send in ip_fragment */
716 	skb->ignore_df = 1;
717 
718 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
719 
720 	return NF_STOLEN;
721 
722  tx_error:
723 	kfree_skb(skb);
724 	return NF_STOLEN;
725 }
726 
727 #ifdef CONFIG_IP_VS_IPV6
728 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)729 ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
730 		     struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
731 {
732 	struct ipv6hdr *iph = ipv6_hdr(skb);
733 
734 	if (__ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, NULL,
735 				  &iph->daddr, NULL,
736 				  ipvsh, 0, IP_VS_RT_MODE_NON_LOCAL) < 0)
737 		goto tx_error;
738 
739 	/* Another hack: avoid icmp_send in ip_fragment */
740 	skb->ignore_df = 1;
741 
742 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
743 
744 	return NF_STOLEN;
745 
746  tx_error:
747 	kfree_skb(skb);
748 	return NF_STOLEN;
749 }
750 #endif
751 
752 /*
753  *      NAT transmitter (only for outside-to-inside nat forwarding)
754  *      Not used for related ICMP
755  */
756 int
ip_vs_nat_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)757 ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
758 	       struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
759 {
760 	struct rtable *rt;		/* Route to the other host */
761 	int local, rc, was_input;
762 
763 	/* check if it is a connection of no-client-port */
764 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
765 		__be16 _pt, *p;
766 
767 		p = skb_header_pointer(skb, ipvsh->len, sizeof(_pt), &_pt);
768 		if (p == NULL)
769 			goto tx_error;
770 		ip_vs_conn_fill_cport(cp, *p);
771 		IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
772 	}
773 
774 	was_input = rt_is_input_route(skb_rtable(skb));
775 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
776 				   IP_VS_RT_MODE_LOCAL |
777 				   IP_VS_RT_MODE_NON_LOCAL |
778 				   IP_VS_RT_MODE_RDR, NULL, ipvsh);
779 	if (local < 0)
780 		goto tx_error;
781 	rt = skb_rtable(skb);
782 	/*
783 	 * Avoid duplicate tuple in reply direction for NAT traffic
784 	 * to local address when connection is sync-ed
785 	 */
786 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
787 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
788 		enum ip_conntrack_info ctinfo;
789 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
790 
791 		if (ct) {
792 			IP_VS_DBG_RL_PKT(10, AF_INET, pp, skb, ipvsh->off,
793 					 "ip_vs_nat_xmit(): "
794 					 "stopping DNAT to local address");
795 			goto tx_error;
796 		}
797 	}
798 #endif
799 
800 	/* From world but DNAT to loopback address? */
801 	if (local && ipv4_is_loopback(cp->daddr.ip) && was_input) {
802 		IP_VS_DBG_RL_PKT(1, AF_INET, pp, skb, ipvsh->off,
803 				 "ip_vs_nat_xmit(): stopping DNAT to loopback "
804 				 "address");
805 		goto tx_error;
806 	}
807 
808 	/* copy-on-write the packet before mangling it */
809 	if (skb_ensure_writable(skb, sizeof(struct iphdr)))
810 		goto tx_error;
811 
812 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
813 		goto tx_error;
814 
815 	/* mangle the packet */
816 	if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp, ipvsh))
817 		goto tx_error;
818 	ip_hdr(skb)->daddr = cp->daddr.ip;
819 	ip_send_check(ip_hdr(skb));
820 
821 	IP_VS_DBG_PKT(10, AF_INET, pp, skb, ipvsh->off, "After DNAT");
822 
823 	/* FIXME: when application helper enlarges the packet and the length
824 	   is larger than the MTU of outgoing device, there will be still
825 	   MTU problem. */
826 
827 	/* Another hack: avoid icmp_send in ip_fragment */
828 	skb->ignore_df = 1;
829 
830 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
831 
832 	return rc;
833 
834   tx_error:
835 	kfree_skb(skb);
836 	return NF_STOLEN;
837 }
838 
839 #ifdef CONFIG_IP_VS_IPV6
840 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)841 ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
842 		  struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
843 {
844 	struct rt6_info *rt;		/* Route to the other host */
845 	int local, rc;
846 
847 	/* check if it is a connection of no-client-port */
848 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT && !ipvsh->fragoffs)) {
849 		__be16 _pt, *p;
850 		p = skb_header_pointer(skb, ipvsh->len, sizeof(_pt), &_pt);
851 		if (p == NULL)
852 			goto tx_error;
853 		ip_vs_conn_fill_cport(cp, *p);
854 		IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
855 	}
856 
857 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
858 				      &cp->daddr.in6,
859 				      NULL, ipvsh, 0,
860 				      IP_VS_RT_MODE_LOCAL |
861 				      IP_VS_RT_MODE_NON_LOCAL |
862 				      IP_VS_RT_MODE_RDR);
863 	if (local < 0)
864 		goto tx_error;
865 	rt = dst_rt6_info(skb_dst(skb));
866 	/*
867 	 * Avoid duplicate tuple in reply direction for NAT traffic
868 	 * to local address when connection is sync-ed
869 	 */
870 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
871 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
872 		enum ip_conntrack_info ctinfo;
873 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
874 
875 		if (ct) {
876 			IP_VS_DBG_RL_PKT(10, AF_INET6, pp, skb, ipvsh->off,
877 					 "ip_vs_nat_xmit_v6(): "
878 					 "stopping DNAT to local address");
879 			goto tx_error;
880 		}
881 	}
882 #endif
883 
884 	/* From world but DNAT to loopback address? */
885 	if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
886 	    ipv6_addr_type(&cp->daddr.in6) & IPV6_ADDR_LOOPBACK) {
887 		IP_VS_DBG_RL_PKT(1, AF_INET6, pp, skb, ipvsh->off,
888 				 "ip_vs_nat_xmit_v6(): "
889 				 "stopping DNAT to loopback address");
890 		goto tx_error;
891 	}
892 
893 	/* copy-on-write the packet before mangling it */
894 	if (skb_ensure_writable(skb, sizeof(struct ipv6hdr)))
895 		goto tx_error;
896 
897 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
898 		goto tx_error;
899 
900 	/* mangle the packet */
901 	if (pp->dnat_handler && !pp->dnat_handler(skb, pp, cp, ipvsh))
902 		goto tx_error;
903 	ipv6_hdr(skb)->daddr = cp->daddr.in6;
904 
905 	IP_VS_DBG_PKT(10, AF_INET6, pp, skb, ipvsh->off, "After DNAT");
906 
907 	/* FIXME: when application helper enlarges the packet and the length
908 	   is larger than the MTU of outgoing device, there will be still
909 	   MTU problem. */
910 
911 	/* Another hack: avoid icmp_send in ip_fragment */
912 	skb->ignore_df = 1;
913 
914 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
915 
916 	return rc;
917 
918 tx_error:
919 	kfree_skb(skb);
920 	return NF_STOLEN;
921 }
922 #endif
923 
924 /* When forwarding a packet, we must ensure that we've got enough headroom
925  * for the encapsulation packet in the skb.  This also gives us an
926  * opportunity to figure out what the payload_len, dsfield, ttl, and df
927  * values should be, so that we won't need to look at the old ip header
928  * again
929  */
930 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)931 ip_vs_prepare_tunneled_skb(struct sk_buff *skb, int skb_af,
932 			   unsigned int max_headroom, __u8 *next_protocol,
933 			   __u32 *payload_len, __u8 *dsfield, __u8 *ttl,
934 			   __be16 *df)
935 {
936 	struct sk_buff *new_skb = NULL;
937 	struct iphdr *old_iph = NULL;
938 	__u8 old_dsfield;
939 #ifdef CONFIG_IP_VS_IPV6
940 	struct ipv6hdr *old_ipv6h = NULL;
941 #endif
942 
943 	ip_vs_drop_early_demux_sk(skb);
944 
945 	if (skb_headroom(skb) < max_headroom || skb_cloned(skb)) {
946 		new_skb = skb_realloc_headroom(skb, max_headroom);
947 		if (!new_skb)
948 			goto error;
949 		if (skb->sk)
950 			skb_set_owner_w(new_skb, skb->sk);
951 		consume_skb(skb);
952 		skb = new_skb;
953 	}
954 
955 #ifdef CONFIG_IP_VS_IPV6
956 	if (skb_af == AF_INET6) {
957 		old_ipv6h = ipv6_hdr(skb);
958 		*next_protocol = IPPROTO_IPV6;
959 		if (payload_len)
960 			*payload_len =
961 				ntohs(old_ipv6h->payload_len) +
962 				sizeof(*old_ipv6h);
963 		old_dsfield = ipv6_get_dsfield(old_ipv6h);
964 		*ttl = old_ipv6h->hop_limit;
965 		if (df)
966 			*df = 0;
967 	} else
968 #endif
969 	{
970 		old_iph = ip_hdr(skb);
971 		/* Copy DF, reset fragment offset and MF */
972 		if (df)
973 			*df = (old_iph->frag_off & htons(IP_DF));
974 		*next_protocol = IPPROTO_IPIP;
975 
976 		/* fix old IP header checksum */
977 		ip_send_check(old_iph);
978 		old_dsfield = ipv4_get_dsfield(old_iph);
979 		*ttl = old_iph->ttl;
980 		if (payload_len)
981 			*payload_len = skb_ip_totlen(skb);
982 	}
983 
984 	/* Implement full-functionality option for ECN encapsulation */
985 	*dsfield = INET_ECN_encapsulate(old_dsfield, old_dsfield);
986 
987 	return skb;
988 error:
989 	kfree_skb(skb);
990 	return ERR_PTR(-ENOMEM);
991 }
992 
__tun_gso_type_mask(int encaps_af,int orig_af)993 static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
994 {
995 	switch (encaps_af) {
996 	case AF_INET:
997 		return SKB_GSO_IPXIP4;
998 	case AF_INET6:
999 		return SKB_GSO_IPXIP6;
1000 	default:
1001 		return 0;
1002 	}
1003 }
1004 
1005 static int
ipvs_gue_encap(struct net * net,struct sk_buff * skb,struct ip_vs_conn * cp,__u8 * next_protocol)1006 ipvs_gue_encap(struct net *net, struct sk_buff *skb,
1007 	       struct ip_vs_conn *cp, __u8 *next_protocol)
1008 {
1009 	__be16 dport;
1010 	__be16 sport = udp_flow_src_port(net, skb, 0, 0, false);
1011 	struct udphdr  *udph;	/* Our new UDP header */
1012 	struct guehdr  *gueh;	/* Our new GUE header */
1013 	size_t hdrlen, optlen = 0;
1014 	void *data;
1015 	bool need_priv = false;
1016 
1017 	if ((cp->dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1018 	    skb->ip_summed == CHECKSUM_PARTIAL) {
1019 		optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1020 		need_priv = true;
1021 	}
1022 
1023 	hdrlen = sizeof(struct guehdr) + optlen;
1024 
1025 	skb_push(skb, hdrlen);
1026 
1027 	gueh = (struct guehdr *)skb->data;
1028 
1029 	gueh->control = 0;
1030 	gueh->version = 0;
1031 	gueh->hlen = optlen >> 2;
1032 	gueh->flags = 0;
1033 	gueh->proto_ctype = *next_protocol;
1034 
1035 	data = &gueh[1];
1036 
1037 	if (need_priv) {
1038 		__be32 *flags = data;
1039 		u16 csum_start = skb_checksum_start_offset(skb);
1040 		__be16 *pd;
1041 
1042 		gueh->flags |= GUE_FLAG_PRIV;
1043 		*flags = 0;
1044 		data += GUE_LEN_PRIV;
1045 
1046 		if (csum_start < hdrlen)
1047 			return -EINVAL;
1048 
1049 		csum_start -= hdrlen;
1050 		pd = data;
1051 		pd[0] = htons(csum_start);
1052 		pd[1] = htons(csum_start + skb->csum_offset);
1053 
1054 		if (!skb_is_gso(skb)) {
1055 			skb->ip_summed = CHECKSUM_NONE;
1056 			skb->encapsulation = 0;
1057 		}
1058 
1059 		*flags |= GUE_PFLAG_REMCSUM;
1060 		data += GUE_PLEN_REMCSUM;
1061 	}
1062 
1063 	skb_push(skb, sizeof(struct udphdr));
1064 	skb_reset_transport_header(skb);
1065 
1066 	udph = udp_hdr(skb);
1067 
1068 	dport = cp->dest->tun_port;
1069 	udph->dest = dport;
1070 	udph->source = sport;
1071 	udph->len = htons(skb->len);
1072 	udph->check = 0;
1073 
1074 	*next_protocol = IPPROTO_UDP;
1075 
1076 	return 0;
1077 }
1078 
1079 static void
ipvs_gre_encap(struct net * net,struct sk_buff * skb,struct ip_vs_conn * cp,__u8 * next_protocol)1080 ipvs_gre_encap(struct net *net, struct sk_buff *skb,
1081 	       struct ip_vs_conn *cp, __u8 *next_protocol)
1082 {
1083 	__be16 proto = *next_protocol == IPPROTO_IPIP ?
1084 				htons(ETH_P_IP) : htons(ETH_P_IPV6);
1085 	IP_TUNNEL_DECLARE_FLAGS(tflags) = { };
1086 	size_t hdrlen;
1087 
1088 	if (cp->dest->tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1089 		__set_bit(IP_TUNNEL_CSUM_BIT, tflags);
1090 
1091 	hdrlen = gre_calc_hlen(tflags);
1092 	gre_build_header(skb, hdrlen, tflags, proto, 0, 0);
1093 
1094 	*next_protocol = IPPROTO_GRE;
1095 }
1096 
1097 /*
1098  *   IP Tunneling transmitter
1099  *
1100  *   This function encapsulates the packet in a new IP packet, its
1101  *   destination will be set to cp->daddr. Most code of this function
1102  *   is taken from ipip.c.
1103  *
1104  *   It is used in VS/TUN cluster. The load balancer selects a real
1105  *   server from a cluster based on a scheduling algorithm,
1106  *   encapsulates the request packet and forwards it to the selected
1107  *   server. For example, all real servers are configured with
1108  *   "ifconfig tunl0 <Virtual IP Address> up". When the server receives
1109  *   the encapsulated packet, it will decapsulate the packet, processe
1110  *   the request and return the response packets directly to the client
1111  *   without passing the load balancer. This can greatly increase the
1112  *   scalability of virtual server.
1113  *
1114  *   Used for ANY protocol
1115  */
1116 int
ip_vs_tunnel_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1117 ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1118 		  struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1119 {
1120 	struct netns_ipvs *ipvs = cp->ipvs;
1121 	struct net *net = ipvs->net;
1122 	struct rtable *rt;			/* Route to the other host */
1123 	__be32 saddr;				/* Source for tunnel */
1124 	struct net_device *tdev;		/* Device to other host */
1125 	__u8 next_protocol = 0;
1126 	__u8 dsfield = 0;
1127 	__u8 ttl = 0;
1128 	__be16 df = 0;
1129 	__be16 *dfp = NULL;
1130 	struct iphdr  *iph;			/* Our new IP header */
1131 	unsigned int max_headroom;		/* The extra header space needed */
1132 	int ret, local;
1133 	int tun_type, gso_type;
1134 	int tun_flags;
1135 
1136 	local = __ip_vs_get_out_rt(ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
1137 				   IP_VS_RT_MODE_LOCAL |
1138 				   IP_VS_RT_MODE_NON_LOCAL |
1139 				   IP_VS_RT_MODE_CONNECT |
1140 				   IP_VS_RT_MODE_TUNNEL, &saddr, ipvsh);
1141 	if (local < 0)
1142 		goto tx_error;
1143 	if (local)
1144 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
1145 
1146 	rt = skb_rtable(skb);
1147 	tdev = rt->dst.dev;
1148 
1149 	/*
1150 	 * Okay, now see if we can stuff it in the buffer as-is.
1151 	 */
1152 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
1153 
1154 	tun_type = cp->dest->tun_type;
1155 	tun_flags = cp->dest->tun_flags;
1156 
1157 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1158 		size_t gue_hdrlen, gue_optlen = 0;
1159 
1160 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1161 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1162 			gue_optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1163 		}
1164 		gue_hdrlen = sizeof(struct guehdr) + gue_optlen;
1165 
1166 		max_headroom += sizeof(struct udphdr) + gue_hdrlen;
1167 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1168 		IP_TUNNEL_DECLARE_FLAGS(tflags) = { };
1169 		size_t gre_hdrlen;
1170 
1171 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1172 			__set_bit(IP_TUNNEL_CSUM_BIT, tflags);
1173 		gre_hdrlen = gre_calc_hlen(tflags);
1174 
1175 		max_headroom += gre_hdrlen;
1176 	}
1177 
1178 	/* We only care about the df field if sysctl_pmtu_disc(ipvs) is set */
1179 	dfp = sysctl_pmtu_disc(ipvs) ? &df : NULL;
1180 	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
1181 					 &next_protocol, NULL, &dsfield,
1182 					 &ttl, dfp);
1183 	if (IS_ERR(skb))
1184 		return NF_STOLEN;
1185 
1186 	gso_type = __tun_gso_type_mask(AF_INET, cp->af);
1187 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1188 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1189 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1190 			gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
1191 		else
1192 			gso_type |= SKB_GSO_UDP_TUNNEL;
1193 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1194 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1195 			gso_type |= SKB_GSO_TUNNEL_REMCSUM;
1196 		}
1197 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1198 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1199 			gso_type |= SKB_GSO_GRE_CSUM;
1200 		else
1201 			gso_type |= SKB_GSO_GRE;
1202 	}
1203 
1204 	if (iptunnel_handle_offloads(skb, gso_type))
1205 		goto tx_error;
1206 
1207 	skb->transport_header = skb->network_header;
1208 
1209 	skb_set_inner_ipproto(skb, next_protocol);
1210 	skb_set_inner_mac_header(skb, skb_inner_network_offset(skb));
1211 
1212 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1213 		bool check = false;
1214 
1215 		if (ipvs_gue_encap(net, skb, cp, &next_protocol))
1216 			goto tx_error;
1217 
1218 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1219 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1220 			check = true;
1221 
1222 		udp_set_csum(!check, skb, saddr, cp->daddr.ip, skb->len);
1223 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE)
1224 		ipvs_gre_encap(net, skb, cp, &next_protocol);
1225 
1226 	skb_push(skb, sizeof(struct iphdr));
1227 	skb_reset_network_header(skb);
1228 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1229 
1230 	/*
1231 	 *	Push down and install the IPIP header.
1232 	 */
1233 	iph			=	ip_hdr(skb);
1234 	iph->version		=	4;
1235 	iph->ihl		=	sizeof(struct iphdr)>>2;
1236 	iph->frag_off		=	df;
1237 	iph->protocol		=	next_protocol;
1238 	iph->tos		=	dsfield;
1239 	iph->daddr		=	cp->daddr.ip;
1240 	iph->saddr		=	saddr;
1241 	iph->ttl		=	ttl;
1242 	ip_select_ident(net, skb, NULL);
1243 
1244 	/* Another hack: avoid icmp_send in ip_fragment */
1245 	skb->ignore_df = 1;
1246 
1247 	ret = ip_vs_tunnel_xmit_prepare(skb, cp);
1248 	if (ret == NF_ACCEPT)
1249 		ip_local_out(net, skb->sk, skb);
1250 	else if (ret == NF_DROP)
1251 		kfree_skb(skb);
1252 
1253 	return NF_STOLEN;
1254 
1255   tx_error:
1256 	kfree_skb(skb);
1257 	return NF_STOLEN;
1258 }
1259 
1260 #ifdef CONFIG_IP_VS_IPV6
1261 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)1262 ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1263 		     struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1264 {
1265 	struct netns_ipvs *ipvs = cp->ipvs;
1266 	struct net *net = ipvs->net;
1267 	struct rt6_info *rt;		/* Route to the other host */
1268 	struct in6_addr saddr;		/* Source for tunnel */
1269 	struct net_device *tdev;	/* Device to other host */
1270 	__u8 next_protocol = 0;
1271 	__u32 payload_len = 0;
1272 	__u8 dsfield = 0;
1273 	__u8 ttl = 0;
1274 	struct ipv6hdr  *iph;		/* Our new IP header */
1275 	unsigned int max_headroom;	/* The extra header space needed */
1276 	int ret, local;
1277 	int tun_type, gso_type;
1278 	int tun_flags;
1279 
1280 	local = __ip_vs_get_out_rt_v6(ipvs, cp->af, skb, cp->dest,
1281 				      &cp->daddr.in6,
1282 				      &saddr, ipvsh, 1,
1283 				      IP_VS_RT_MODE_LOCAL |
1284 				      IP_VS_RT_MODE_NON_LOCAL |
1285 				      IP_VS_RT_MODE_TUNNEL);
1286 	if (local < 0)
1287 		goto tx_error;
1288 	if (local)
1289 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
1290 
1291 	rt = dst_rt6_info(skb_dst(skb));
1292 	tdev = rt->dst.dev;
1293 
1294 	/*
1295 	 * Okay, now see if we can stuff it in the buffer as-is.
1296 	 */
1297 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct ipv6hdr);
1298 
1299 	tun_type = cp->dest->tun_type;
1300 	tun_flags = cp->dest->tun_flags;
1301 
1302 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1303 		size_t gue_hdrlen, gue_optlen = 0;
1304 
1305 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1306 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1307 			gue_optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;
1308 		}
1309 		gue_hdrlen = sizeof(struct guehdr) + gue_optlen;
1310 
1311 		max_headroom += sizeof(struct udphdr) + gue_hdrlen;
1312 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1313 		IP_TUNNEL_DECLARE_FLAGS(tflags) = { };
1314 		size_t gre_hdrlen;
1315 
1316 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1317 			__set_bit(IP_TUNNEL_CSUM_BIT, tflags);
1318 		gre_hdrlen = gre_calc_hlen(tflags);
1319 
1320 		max_headroom += gre_hdrlen;
1321 	}
1322 
1323 	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
1324 					 &next_protocol, &payload_len,
1325 					 &dsfield, &ttl, NULL);
1326 	if (IS_ERR(skb))
1327 		return NF_STOLEN;
1328 
1329 	gso_type = __tun_gso_type_mask(AF_INET6, cp->af);
1330 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1331 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1332 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1333 			gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
1334 		else
1335 			gso_type |= SKB_GSO_UDP_TUNNEL;
1336 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) &&
1337 		    skb->ip_summed == CHECKSUM_PARTIAL) {
1338 			gso_type |= SKB_GSO_TUNNEL_REMCSUM;
1339 		}
1340 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {
1341 		if (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM)
1342 			gso_type |= SKB_GSO_GRE_CSUM;
1343 		else
1344 			gso_type |= SKB_GSO_GRE;
1345 	}
1346 
1347 	if (iptunnel_handle_offloads(skb, gso_type))
1348 		goto tx_error;
1349 
1350 	skb->transport_header = skb->network_header;
1351 
1352 	skb_set_inner_ipproto(skb, next_protocol);
1353 	skb_set_inner_mac_header(skb, skb_inner_network_offset(skb));
1354 
1355 	if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {
1356 		bool check = false;
1357 
1358 		if (ipvs_gue_encap(net, skb, cp, &next_protocol))
1359 			goto tx_error;
1360 
1361 		if ((tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_CSUM) ||
1362 		    (tun_flags & IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM))
1363 			check = true;
1364 
1365 		udp6_set_csum(!check, skb, &saddr, &cp->daddr.in6, skb->len);
1366 	} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE)
1367 		ipvs_gre_encap(net, skb, cp, &next_protocol);
1368 
1369 	skb_push(skb, sizeof(struct ipv6hdr));
1370 	skb_reset_network_header(skb);
1371 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
1372 
1373 	/*
1374 	 *	Push down and install the IPIP header.
1375 	 */
1376 	iph			=	ipv6_hdr(skb);
1377 	iph->version		=	6;
1378 	iph->nexthdr		=	next_protocol;
1379 	iph->payload_len	=	htons(payload_len);
1380 	memset(&iph->flow_lbl, 0, sizeof(iph->flow_lbl));
1381 	ipv6_change_dsfield(iph, 0, dsfield);
1382 	iph->daddr = cp->daddr.in6;
1383 	iph->saddr = saddr;
1384 	iph->hop_limit		=	ttl;
1385 
1386 	/* Another hack: avoid icmp_send in ip_fragment */
1387 	skb->ignore_df = 1;
1388 
1389 	ret = ip_vs_tunnel_xmit_prepare(skb, cp);
1390 	if (ret == NF_ACCEPT)
1391 		ip6_local_out(net, skb->sk, skb);
1392 	else if (ret == NF_DROP)
1393 		kfree_skb(skb);
1394 
1395 	return NF_STOLEN;
1396 
1397 tx_error:
1398 	kfree_skb(skb);
1399 	return NF_STOLEN;
1400 }
1401 #endif
1402 
1403 
1404 /*
1405  *      Direct Routing transmitter
1406  *      Used for ANY protocol
1407  */
1408 int
ip_vs_dr_xmit(struct sk_buff * skb,struct ip_vs_conn * cp,struct ip_vs_protocol * pp,struct ip_vs_iphdr * ipvsh)1409 ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1410 	      struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1411 {
1412 	int local;
1413 
1414 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
1415 				   IP_VS_RT_MODE_LOCAL |
1416 				   IP_VS_RT_MODE_NON_LOCAL |
1417 				   IP_VS_RT_MODE_KNOWN_NH, NULL, ipvsh);
1418 	if (local < 0)
1419 		goto tx_error;
1420 	if (local)
1421 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
1422 
1423 	ip_send_check(ip_hdr(skb));
1424 
1425 	/* Another hack: avoid icmp_send in ip_fragment */
1426 	skb->ignore_df = 1;
1427 
1428 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
1429 
1430 	return NF_STOLEN;
1431 
1432   tx_error:
1433 	kfree_skb(skb);
1434 	return NF_STOLEN;
1435 }
1436 
1437 #ifdef CONFIG_IP_VS_IPV6
1438 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)1439 ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1440 		 struct ip_vs_protocol *pp, struct ip_vs_iphdr *ipvsh)
1441 {
1442 	int local;
1443 
1444 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
1445 				      &cp->daddr.in6,
1446 				      NULL, ipvsh, 0,
1447 				      IP_VS_RT_MODE_LOCAL |
1448 				      IP_VS_RT_MODE_NON_LOCAL |
1449 				      IP_VS_RT_MODE_KNOWN_NH);
1450 	if (local < 0)
1451 		goto tx_error;
1452 	if (local)
1453 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
1454 
1455 	/* Another hack: avoid icmp_send in ip_fragment */
1456 	skb->ignore_df = 1;
1457 
1458 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
1459 
1460 	return NF_STOLEN;
1461 
1462 tx_error:
1463 	kfree_skb(skb);
1464 	return NF_STOLEN;
1465 }
1466 #endif
1467 
1468 
1469 /*
1470  *	ICMP packet transmitter
1471  *	called by the ip_vs_in_icmp
1472  */
1473 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)1474 ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
1475 		struct ip_vs_protocol *pp, int offset, unsigned int hooknum,
1476 		struct ip_vs_iphdr *iph)
1477 {
1478 	struct rtable	*rt;	/* Route to the other host */
1479 	int rc;
1480 	int local;
1481 	int rt_mode, was_input;
1482 
1483 	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
1484 	   forwarded directly here, because there is no need to
1485 	   translate address/port back */
1486 	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
1487 		if (cp->packet_xmit)
1488 			rc = cp->packet_xmit(skb, cp, pp, iph);
1489 		else
1490 			rc = NF_ACCEPT;
1491 		/* do not touch skb anymore */
1492 		atomic_inc(&cp->in_pkts);
1493 		return rc;
1494 	}
1495 
1496 	/*
1497 	 * mangle and send the packet here (only for VS/NAT)
1498 	 */
1499 	was_input = rt_is_input_route(skb_rtable(skb));
1500 
1501 	/* LOCALNODE from FORWARD hook is not supported */
1502 	rt_mode = (hooknum != NF_INET_FORWARD) ?
1503 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
1504 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
1505 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip, rt_mode,
1506 				   NULL, iph);
1507 	if (local < 0)
1508 		goto tx_error;
1509 	rt = skb_rtable(skb);
1510 
1511 	/*
1512 	 * Avoid duplicate tuple in reply direction for NAT traffic
1513 	 * to local address when connection is sync-ed
1514 	 */
1515 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
1516 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
1517 		enum ip_conntrack_info ctinfo;
1518 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1519 
1520 		if (ct) {
1521 			IP_VS_DBG(10, "%s(): "
1522 				  "stopping DNAT to local address %pI4\n",
1523 				  __func__, &cp->daddr.ip);
1524 			goto tx_error;
1525 		}
1526 	}
1527 #endif
1528 
1529 	/* From world but DNAT to loopback address? */
1530 	if (local && ipv4_is_loopback(cp->daddr.ip) && was_input) {
1531 		IP_VS_DBG(1, "%s(): "
1532 			  "stopping DNAT to loopback %pI4\n",
1533 			  __func__, &cp->daddr.ip);
1534 		goto tx_error;
1535 	}
1536 
1537 	/* copy-on-write the packet before mangling it */
1538 	if (skb_ensure_writable(skb, offset))
1539 		goto tx_error;
1540 
1541 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
1542 		goto tx_error;
1543 
1544 	ip_vs_nat_icmp(skb, pp, cp, 0);
1545 
1546 	/* Another hack: avoid icmp_send in ip_fragment */
1547 	skb->ignore_df = 1;
1548 
1549 	return ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
1550 
1551   tx_error:
1552 	kfree_skb(skb);
1553 	rc = NF_STOLEN;
1554 	return rc;
1555 }
1556 
1557 #ifdef CONFIG_IP_VS_IPV6
1558 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)1559 ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
1560 		struct ip_vs_protocol *pp, int offset, unsigned int hooknum,
1561 		struct ip_vs_iphdr *ipvsh)
1562 {
1563 	struct rt6_info	*rt;	/* Route to the other host */
1564 	int rc;
1565 	int local;
1566 	int rt_mode;
1567 
1568 	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
1569 	   forwarded directly here, because there is no need to
1570 	   translate address/port back */
1571 	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
1572 		if (cp->packet_xmit)
1573 			rc = cp->packet_xmit(skb, cp, pp, ipvsh);
1574 		else
1575 			rc = NF_ACCEPT;
1576 		/* do not touch skb anymore */
1577 		atomic_inc(&cp->in_pkts);
1578 		return rc;
1579 	}
1580 
1581 	/*
1582 	 * mangle and send the packet here (only for VS/NAT)
1583 	 */
1584 
1585 	/* LOCALNODE from FORWARD hook is not supported */
1586 	rt_mode = (hooknum != NF_INET_FORWARD) ?
1587 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
1588 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
1589 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
1590 				      &cp->daddr.in6, NULL, ipvsh, 0, rt_mode);
1591 	if (local < 0)
1592 		goto tx_error;
1593 	rt = dst_rt6_info(skb_dst(skb));
1594 	/*
1595 	 * Avoid duplicate tuple in reply direction for NAT traffic
1596 	 * to local address when connection is sync-ed
1597 	 */
1598 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
1599 	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
1600 		enum ip_conntrack_info ctinfo;
1601 		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
1602 
1603 		if (ct) {
1604 			IP_VS_DBG(10, "%s(): "
1605 				  "stopping DNAT to local address %pI6\n",
1606 				  __func__, &cp->daddr.in6);
1607 			goto tx_error;
1608 		}
1609 	}
1610 #endif
1611 
1612 	/* From world but DNAT to loopback address? */
1613 	if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
1614 	    ipv6_addr_type(&cp->daddr.in6) & IPV6_ADDR_LOOPBACK) {
1615 		IP_VS_DBG(1, "%s(): "
1616 			  "stopping DNAT to loopback %pI6\n",
1617 			  __func__, &cp->daddr.in6);
1618 		goto tx_error;
1619 	}
1620 
1621 	/* copy-on-write the packet before mangling it */
1622 	if (skb_ensure_writable(skb, offset))
1623 		goto tx_error;
1624 
1625 	if (skb_cow(skb, rt->dst.dev->hard_header_len))
1626 		goto tx_error;
1627 
1628 	ip_vs_nat_icmp_v6(skb, pp, cp, 0);
1629 
1630 	/* Another hack: avoid icmp_send in ip_fragment */
1631 	skb->ignore_df = 1;
1632 
1633 	return ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
1634 
1635 tx_error:
1636 	kfree_skb(skb);
1637 	rc = NF_STOLEN;
1638 	return rc;
1639 }
1640 #endif
1641