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Linux/net/ipv6/netfilter.c

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  1 /*
  2  * IPv6 specific functions of netfilter core
  3  *
  4  * Rusty Russell (C) 2000 -- This code is GPL.
  5  * Patrick McHardy (C) 2006-2012
  6  */
  7 #include <linux/kernel.h>
  8 #include <linux/init.h>
  9 #include <linux/ipv6.h>
 10 #include <linux/netfilter.h>
 11 #include <linux/netfilter_ipv6.h>
 12 #include <linux/export.h>
 13 #include <net/addrconf.h>
 14 #include <net/dst.h>
 15 #include <net/ipv6.h>
 16 #include <net/ip6_route.h>
 17 #include <net/xfrm.h>
 18 #include <net/netfilter/nf_queue.h>
 19 #include <net/netfilter/nf_conntrack_bridge.h>
 20 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
 21 #include "../bridge/br_private.h"
 22 
 23 int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff *skb)
 24 {
 25         const struct ipv6hdr *iph = ipv6_hdr(skb);
 26         struct sock *sk = sk_to_full_sk(sk_partial);
 27         struct flow_keys flkeys;
 28         unsigned int hh_len;
 29         struct dst_entry *dst;
 30         int strict = (ipv6_addr_type(&iph->daddr) &
 31                       (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
 32         struct flowi6 fl6 = {
 33                 .flowi6_oif = sk && sk->sk_bound_dev_if ? sk->sk_bound_dev_if :
 34                         strict ? skb_dst(skb)->dev->ifindex : 0,
 35                 .flowi6_mark = skb->mark,
 36                 .flowi6_uid = sock_net_uid(net, sk),
 37                 .daddr = iph->daddr,
 38                 .saddr = iph->saddr,
 39         };
 40         int err;
 41 
 42         fib6_rules_early_flow_dissect(net, skb, &fl6, &flkeys);
 43         dst = ip6_route_output(net, sk, &fl6);
 44         err = dst->error;
 45         if (err) {
 46                 IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
 47                 net_dbg_ratelimited("ip6_route_me_harder: No more route\n");
 48                 dst_release(dst);
 49                 return err;
 50         }
 51 
 52         /* Drop old route. */
 53         skb_dst_drop(skb);
 54 
 55         skb_dst_set(skb, dst);
 56 
 57 #ifdef CONFIG_XFRM
 58         if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 59             xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
 60                 skb_dst_set(skb, NULL);
 61                 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
 62                 if (IS_ERR(dst))
 63                         return PTR_ERR(dst);
 64                 skb_dst_set(skb, dst);
 65         }
 66 #endif
 67 
 68         /* Change in oif may mean change in hh_len. */
 69         hh_len = skb_dst(skb)->dev->hard_header_len;
 70         if (skb_headroom(skb) < hh_len &&
 71             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
 72                              0, GFP_ATOMIC))
 73                 return -ENOMEM;
 74 
 75         return 0;
 76 }
 77 EXPORT_SYMBOL(ip6_route_me_harder);
 78 
 79 static int nf_ip6_reroute(struct sk_buff *skb,
 80                           const struct nf_queue_entry *entry)
 81 {
 82         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
 83 
 84         if (entry->state.hook == NF_INET_LOCAL_OUT) {
 85                 const struct ipv6hdr *iph = ipv6_hdr(skb);
 86                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
 87                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
 88                     skb->mark != rt_info->mark)
 89                         return ip6_route_me_harder(entry->state.net, entry->state.sk, skb);
 90         }
 91         return 0;
 92 }
 93 
 94 int __nf_ip6_route(struct net *net, struct dst_entry **dst,
 95                    struct flowi *fl, bool strict)
 96 {
 97         static const struct ipv6_pinfo fake_pinfo;
 98         static const struct inet_sock fake_sk = {
 99                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
100                 .sk.sk_bound_dev_if = 1,
101                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
102         };
103         const void *sk = strict ? &fake_sk : NULL;
104         struct dst_entry *result;
105         int err;
106 
107         result = ip6_route_output(net, sk, &fl->u.ip6);
108         err = result->error;
109         if (err)
110                 dst_release(result);
111         else
112                 *dst = result;
113         return err;
114 }
115 EXPORT_SYMBOL_GPL(__nf_ip6_route);
116 
117 int br_ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
118                     struct nf_bridge_frag_data *data,
119                     int (*output)(struct net *, struct sock *sk,
120                                   const struct nf_bridge_frag_data *data,
121                                   struct sk_buff *))
122 {
123         int frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
124         ktime_t tstamp = skb->tstamp;
125         struct ip6_frag_state state;
126         u8 *prevhdr, nexthdr = 0;
127         unsigned int mtu, hlen;
128         int hroom, err = 0;
129         __be32 frag_id;
130 
131         err = ip6_find_1stfragopt(skb, &prevhdr);
132         if (err < 0)
133                 goto blackhole;
134         hlen = err;
135         nexthdr = *prevhdr;
136 
137         mtu = skb->dev->mtu;
138         if (frag_max_size > mtu ||
139             frag_max_size < IPV6_MIN_MTU)
140                 goto blackhole;
141 
142         mtu = frag_max_size;
143         if (mtu < hlen + sizeof(struct frag_hdr) + 8)
144                 goto blackhole;
145         mtu -= hlen + sizeof(struct frag_hdr);
146 
147         frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr,
148                                     &ipv6_hdr(skb)->saddr);
149 
150         if (skb->ip_summed == CHECKSUM_PARTIAL &&
151             (err = skb_checksum_help(skb)))
152                 goto blackhole;
153 
154         hroom = LL_RESERVED_SPACE(skb->dev);
155         if (skb_has_frag_list(skb)) {
156                 unsigned int first_len = skb_pagelen(skb);
157                 struct ip6_fraglist_iter iter;
158                 struct sk_buff *frag2;
159 
160                 if (first_len - hlen > mtu ||
161                     skb_headroom(skb) < (hroom + sizeof(struct frag_hdr)))
162                         goto blackhole;
163 
164                 if (skb_cloned(skb))
165                         goto slow_path;
166 
167                 skb_walk_frags(skb, frag2) {
168                         if (frag2->len > mtu ||
169                             skb_headroom(frag2) < (hlen + hroom + sizeof(struct frag_hdr)))
170                                 goto blackhole;
171 
172                         /* Partially cloned skb? */
173                         if (skb_shared(frag2))
174                                 goto slow_path;
175                 }
176 
177                 err = ip6_fraglist_init(skb, hlen, prevhdr, nexthdr, frag_id,
178                                         &iter);
179                 if (err < 0)
180                         goto blackhole;
181 
182                 for (;;) {
183                         /* Prepare header of the next frame,
184                          * before previous one went down.
185                          */
186                         if (iter.frag)
187                                 ip6_fraglist_prepare(skb, &iter);
188 
189                         skb->tstamp = tstamp;
190                         err = output(net, sk, data, skb);
191                         if (err || !iter.frag)
192                                 break;
193 
194                         skb = ip6_fraglist_next(&iter);
195                 }
196 
197                 kfree(iter.tmp_hdr);
198                 if (!err)
199                         return 0;
200 
201                 kfree_skb_list(iter.frag);
202                 return err;
203         }
204 slow_path:
205         /* This is a linearized skbuff, the original geometry is lost for us.
206          * This may also be a clone skbuff, we could preserve the geometry for
207          * the copies but probably not worth the effort.
208          */
209         ip6_frag_init(skb, hlen, mtu, skb->dev->needed_tailroom,
210                       LL_RESERVED_SPACE(skb->dev), prevhdr, nexthdr, frag_id,
211                       &state);
212 
213         while (state.left > 0) {
214                 struct sk_buff *skb2;
215 
216                 skb2 = ip6_frag_next(skb, &state);
217                 if (IS_ERR(skb2)) {
218                         err = PTR_ERR(skb2);
219                         goto blackhole;
220                 }
221 
222                 skb2->tstamp = tstamp;
223                 err = output(net, sk, data, skb2);
224                 if (err)
225                         goto blackhole;
226         }
227         consume_skb(skb);
228         return err;
229 
230 blackhole:
231         kfree_skb(skb);
232         return 0;
233 }
234 EXPORT_SYMBOL_GPL(br_ip6_fragment);
235 
236 static const struct nf_ipv6_ops ipv6ops = {
237 #if IS_MODULE(CONFIG_IPV6)
238         .chk_addr               = ipv6_chk_addr,
239         .route_me_harder        = ip6_route_me_harder,
240         .dev_get_saddr          = ipv6_dev_get_saddr,
241         .route                  = __nf_ip6_route,
242 #if IS_ENABLED(CONFIG_SYN_COOKIES)
243         .cookie_init_sequence   = __cookie_v6_init_sequence,
244         .cookie_v6_check        = __cookie_v6_check,
245 #endif
246 #endif
247         .route_input            = ip6_route_input,
248         .fragment               = ip6_fragment,
249         .reroute                = nf_ip6_reroute,
250 #if IS_MODULE(CONFIG_IPV6)
251         .br_fragment            = br_ip6_fragment,
252 #endif
253 };
254 
255 int __init ipv6_netfilter_init(void)
256 {
257         RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
258         return 0;
259 }
260 
261 /* This can be called from inet6_init() on errors, so it cannot
262  * be marked __exit. -DaveM
263  */
264 void ipv6_netfilter_fini(void)
265 {
266         RCU_INIT_POINTER(nf_ipv6_ops, NULL);
267 }
268 

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