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