net/ipv6/netfilter.c

   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/ip6_checksum.h>
  19 #include <net/netfilter/nf_queue.h>
  20
  21 int ip6_route_me_harder(struct net *net, struct sk_buff *skb)
  22 {
  23         const struct ipv6hdr *iph = ipv6_hdr(skb);
  24         struct sock *sk = sk_to_full_sk(skb->sk);
  25         unsigned int hh_len;
  26         struct dst_entry *dst;
  27         struct flowi6 fl6 = {
  28                 .flowi6_oif = sk ? sk->sk_bound_dev_if : 0,
  29                 .flowi6_mark = skb->mark,
  30                 .flowi6_uid = sock_net_uid(net, sk),
  31                 .daddr = iph->daddr,
  32                 .saddr = iph->saddr,
  33         };
  34         int err;
  35
  36         dst = ip6_route_output(net, sk, &fl6);
  37         err = dst->error;
  38         if (err) {
  39                 IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  40                 net_dbg_ratelimited("ip6_route_me_harder: No more route\n");
  41                 dst_release(dst);
  42                 return err;
  43         }
  44
  45         /* Drop old route. */
  46         skb_dst_drop(skb);
  47
  48         skb_dst_set(skb, dst);
  49
  50 #ifdef CONFIG_XFRM
  51         if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
  52             xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
  53                 skb_dst_set(skb, NULL);
  54                 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
  55                 if (IS_ERR(dst))
  56                         return PTR_ERR(dst);
  57                 skb_dst_set(skb, dst);
  58         }
  59 #endif
  60
  61         /* Change in oif may mean change in hh_len. */
  62         hh_len = skb_dst(skb)->dev->hard_header_len;
  63         if (skb_headroom(skb) < hh_len &&
  64             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  65                              0, GFP_ATOMIC))
  66                 return -ENOMEM;
  67
  68         return 0;
  69 }
  70 EXPORT_SYMBOL(ip6_route_me_harder);
  71
  72 static int nf_ip6_reroute(struct sk_buff *skb,
  73                           const struct nf_queue_entry *entry)
  74 {
  75         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  76
  77         if (entry->state.hook == NF_INET_LOCAL_OUT) {
  78                 const struct ipv6hdr *iph = ipv6_hdr(skb);
  79                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
  80                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
  81                     skb->mark != rt_info->mark)
  82                         return ip6_route_me_harder(entry->state.net, skb);
  83         }
  84         return 0;
  85 }
  86
  87 static int nf_ip6_route(struct net *net, struct dst_entry **dst,
  88                         struct flowi *fl, bool strict)
  89 {
  90         static const struct ipv6_pinfo fake_pinfo;
  91         static const struct inet_sock fake_sk = {
  92                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
  93                 .sk.sk_bound_dev_if = 1,
  94                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
  95         };
  96         const void *sk = strict ? &fake_sk : NULL;
  97         struct dst_entry *result;
  98         int err;
  99
 100         result = ip6_route_output(net, sk, &fl->u.ip6);
 101         err = result->error;
 102         if (err)
 103                 dst_release(result);
 104         else
 105                 *dst = result;
 106         return err;
 107 }
 108
 109 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
 110                              unsigned int dataoff, u_int8_t protocol)
 111 {
 112         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 113         __sum16 csum = 0;
 114
 115         switch (skb->ip_summed) {
 116         case CHECKSUM_COMPLETE:
 117                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 118                         break;
 119                 if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 120                                      skb->len - dataoff, protocol,
 121                                      csum_sub(skb->csum,
 122                                               skb_checksum(skb, 0,
 123                                                            dataoff, 0)))) {
 124                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 125                         break;
 126                 }
 127                 /* fall through */
 128         case CHECKSUM_NONE:
 129                 skb->csum = ~csum_unfold(
 130                                 csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 131                                              skb->len - dataoff,
 132                                              protocol,
 133                                              csum_sub(0,
 134                                                       skb_checksum(skb, 0,
 135                                                                    dataoff, 0))));
 136                 csum = __skb_checksum_complete(skb);
 137         }
 138         return csum;
 139 }
 140 EXPORT_SYMBOL(nf_ip6_checksum);
 141
 142 static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
 143                                        unsigned int dataoff, unsigned int len,
 144                                        u_int8_t protocol)
 145 {
 146         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 147         __wsum hsum;
 148         __sum16 csum = 0;
 149
 150         switch (skb->ip_summed) {
 151         case CHECKSUM_COMPLETE:
 152                 if (len == skb->len - dataoff)
 153                         return nf_ip6_checksum(skb, hook, dataoff, protocol);
 154                 /* fall through */
 155         case CHECKSUM_NONE:
 156                 hsum = skb_checksum(skb, 0, dataoff, 0);
 157                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
 158                                                          &ip6h->daddr,
 159                                                          skb->len - dataoff,
 160                                                          protocol,
 161                                                          csum_sub(0, hsum)));
 162                 skb->ip_summed = CHECKSUM_NONE;
 163                 return __skb_checksum_complete_head(skb, dataoff + len);
 164         }
 165         return csum;
 166 };
 167
 168 static const struct nf_ipv6_ops ipv6ops = {
 169         .chk_addr               = ipv6_chk_addr,
 170         .route_input            = ip6_route_input,
 171         .fragment               = ip6_fragment,
 172         .checksum               = nf_ip6_checksum,
 173         .checksum_partial       = nf_ip6_checksum_partial,
 174         .route                  = nf_ip6_route,
 175         .reroute                = nf_ip6_reroute,
 176 };
 177
 178 int __init ipv6_netfilter_init(void)
 179 {
 180         RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
 181         return 0;
 182 }
 183
 184 /* This can be called from inet6_init() on errors, so it cannot
 185  * be marked __exit. -DaveM
 186  */
 187 void ipv6_netfilter_fini(void)
 188 {
 189         RCU_INIT_POINTER(nf_ipv6_ops, NULL);
 190 }