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/dst.h>
  14 #include <net/ipv6.h>
  15 #include <net/ip6_route.h>
  16 #include <net/xfrm.h>
  17 #include <net/ip6_checksum.h>
  18 #include <net/netfilter/nf_queue.h>
  19
  20 int ip6_route_me_harder(struct sk_buff *skb)
  21 {
  22         struct net *net = dev_net(skb_dst(skb)->dev);
  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                 .daddr = iph->daddr,
  30                 .saddr = iph->saddr,
  31         };
  32
  33         dst = ip6_route_output(net, skb->sk, &fl6);
  34         if (dst->error) {
  35                 IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  36                 LIMIT_NETDEBUG(KERN_DEBUG "ip6_route_me_harder: No more route.\n");
  37                 dst_release(dst);
  38                 return dst->error;
  39         }
  40
  41         /* Drop old route. */
  42         skb_dst_drop(skb);
  43
  44         skb_dst_set(skb, dst);
  45
  46 #ifdef CONFIG_XFRM
  47         if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
  48             xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
  49                 skb_dst_set(skb, NULL);
  50                 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), skb->sk, 0);
  51                 if (IS_ERR(dst))
  52                         return PTR_ERR(dst);
  53                 skb_dst_set(skb, dst);
  54         }
  55 #endif
  56
  57         /* Change in oif may mean change in hh_len. */
  58         hh_len = skb_dst(skb)->dev->hard_header_len;
  59         if (skb_headroom(skb) < hh_len &&
  60             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  61                              0, GFP_ATOMIC))
  62                 return -ENOMEM;
  63
  64         return 0;
  65 }
  66 EXPORT_SYMBOL(ip6_route_me_harder);
  67
  68 /*
  69  * Extra routing may needed on local out, as the QUEUE target never
  70  * returns control to the table.
  71  */
  72
  73 struct ip6_rt_info {
  74         struct in6_addr daddr;
  75         struct in6_addr saddr;
  76         u_int32_t mark;
  77 };
  78
  79 static void nf_ip6_saveroute(const struct sk_buff *skb,
  80                              struct nf_queue_entry *entry)
  81 {
  82         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  83
  84         if (entry->hook == NF_INET_LOCAL_OUT) {
  85                 const struct ipv6hdr *iph = ipv6_hdr(skb);
  86
  87                 rt_info->daddr = iph->daddr;
  88                 rt_info->saddr = iph->saddr;
  89                 rt_info->mark = skb->mark;
  90         }
  91 }
  92
  93 static int nf_ip6_reroute(struct sk_buff *skb,
  94                           const struct nf_queue_entry *entry)
  95 {
  96         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  97
  98         if (entry->hook == NF_INET_LOCAL_OUT) {
  99                 const struct ipv6hdr *iph = ipv6_hdr(skb);
 100                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
 101                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
 102                     skb->mark != rt_info->mark)
 103                         return ip6_route_me_harder(skb);
 104         }
 105         return 0;
 106 }
 107
 108 static int nf_ip6_route(struct net *net, struct dst_entry **dst,
 109                         struct flowi *fl, bool strict)
 110 {
 111         static const struct ipv6_pinfo fake_pinfo;
 112         static const struct inet_sock fake_sk = {
 113                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
 114                 .sk.sk_bound_dev_if = 1,
 115                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
 116         };
 117         const void *sk = strict ? &fake_sk : NULL;
 118         struct dst_entry *result;
 119         int err;
 120
 121         result = ip6_route_output(net, sk, &fl->u.ip6);
 122         err = result->error;
 123         if (err)
 124                 dst_release(result);
 125         else
 126                 *dst = result;
 127         return err;
 128 }
 129
 130 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
 131                              unsigned int dataoff, u_int8_t protocol)
 132 {
 133         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 134         __sum16 csum = 0;
 135
 136         switch (skb->ip_summed) {
 137         case CHECKSUM_COMPLETE:
 138                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 139                         break;
 140                 if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 141                                      skb->len - dataoff, protocol,
 142                                      csum_sub(skb->csum,
 143                                               skb_checksum(skb, 0,
 144                                                            dataoff, 0)))) {
 145                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 146                         break;
 147                 }
 148                 /* fall through */
 149         case CHECKSUM_NONE:
 150                 skb->csum = ~csum_unfold(
 151                                 csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 152                                              skb->len - dataoff,
 153                                              protocol,
 154                                              csum_sub(0,
 155                                                       skb_checksum(skb, 0,
 156                                                                    dataoff, 0))));
 157                 csum = __skb_checksum_complete(skb);
 158         }
 159         return csum;
 160 }
 161 EXPORT_SYMBOL(nf_ip6_checksum);
 162
 163 static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
 164                                        unsigned int dataoff, unsigned int len,
 165                                        u_int8_t protocol)
 166 {
 167         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 168         __wsum hsum;
 169         __sum16 csum = 0;
 170
 171         switch (skb->ip_summed) {
 172         case CHECKSUM_COMPLETE:
 173                 if (len == skb->len - dataoff)
 174                         return nf_ip6_checksum(skb, hook, dataoff, protocol);
 175                 /* fall through */
 176         case CHECKSUM_NONE:
 177                 hsum = skb_checksum(skb, 0, dataoff, 0);
 178                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
 179                                                          &ip6h->daddr,
 180                                                          skb->len - dataoff,
 181                                                          protocol,
 182                                                          csum_sub(0, hsum)));
 183                 skb->ip_summed = CHECKSUM_NONE;
 184                 return __skb_checksum_complete_head(skb, dataoff + len);
 185         }
 186         return csum;
 187 };
 188
 189 static const struct nf_afinfo nf_ip6_afinfo = {
 190         .family                 = AF_INET6,
 191         .checksum               = nf_ip6_checksum,
 192         .checksum_partial       = nf_ip6_checksum_partial,
 193         .route                  = nf_ip6_route,
 194         .saveroute              = nf_ip6_saveroute,
 195         .reroute                = nf_ip6_reroute,
 196         .route_key_size         = sizeof(struct ip6_rt_info),
 197 };
 198
 199 int __init ipv6_netfilter_init(void)
 200 {
 201         return nf_register_afinfo(&nf_ip6_afinfo);
 202 }
 203
 204 /* This can be called from inet6_init() on errors, so it cannot
 205  * be marked __exit. -DaveM
 206  */
 207 void ipv6_netfilter_fini(void)
 208 {
 209         nf_unregister_afinfo(&nf_ip6_afinfo);
 210 }