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 /*
  73  * Extra routing may needed on local out, as the QUEUE target never
  74  * returns control to the table.
  75  */
  76
  77 struct ip6_rt_info {
  78         struct in6_addr daddr;
  79         struct in6_addr saddr;
  80         u_int32_t mark;
  81 };
  82
  83 static void nf_ip6_saveroute(const struct sk_buff *skb,
  84                              struct nf_queue_entry *entry)
  85 {
  86         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  87
  88         if (entry->state.hook == NF_INET_LOCAL_OUT) {
  89                 const struct ipv6hdr *iph = ipv6_hdr(skb);
  90
  91                 rt_info->daddr = iph->daddr;
  92                 rt_info->saddr = iph->saddr;
  93                 rt_info->mark = skb->mark;
  94         }
  95 }
  96
  97 static int nf_ip6_reroute(struct net *net, struct sk_buff *skb,
  98                           const struct nf_queue_entry *entry)
  99 {
 100         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
 101
 102         if (entry->state.hook == NF_INET_LOCAL_OUT) {
 103                 const struct ipv6hdr *iph = ipv6_hdr(skb);
 104                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
 105                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
 106                     skb->mark != rt_info->mark)
 107                         return ip6_route_me_harder(net, skb);
 108         }
 109         return 0;
 110 }
 111
 112 static int nf_ip6_route(struct net *net, struct dst_entry **dst,
 113                         struct flowi *fl, bool strict)
 114 {
 115         static const struct ipv6_pinfo fake_pinfo;
 116         static const struct inet_sock fake_sk = {
 117                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
 118                 .sk.sk_bound_dev_if = 1,
 119                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
 120         };
 121         const void *sk = strict ? &fake_sk : NULL;
 122         struct dst_entry *result;
 123         int err;
 124
 125         result = ip6_route_output(net, sk, &fl->u.ip6);
 126         err = result->error;
 127         if (err)
 128                 dst_release(result);
 129         else
 130                 *dst = result;
 131         return err;
 132 }
 133
 134 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
 135                              unsigned int dataoff, u_int8_t protocol)
 136 {
 137         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 138         __sum16 csum = 0;
 139
 140         switch (skb->ip_summed) {
 141         case CHECKSUM_COMPLETE:
 142                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 143                         break;
 144                 if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 145                                      skb->len - dataoff, protocol,
 146                                      csum_sub(skb->csum,
 147                                               skb_checksum(skb, 0,
 148                                                            dataoff, 0)))) {
 149                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 150                         break;
 151                 }
 152                 /* fall through */
 153         case CHECKSUM_NONE:
 154                 skb->csum = ~csum_unfold(
 155                                 csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 156                                              skb->len - dataoff,
 157                                              protocol,
 158                                              csum_sub(0,
 159                                                       skb_checksum(skb, 0,
 160                                                                    dataoff, 0))));
 161                 csum = __skb_checksum_complete(skb);
 162         }
 163         return csum;
 164 }
 165 EXPORT_SYMBOL(nf_ip6_checksum);
 166
 167 static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
 168                                        unsigned int dataoff, unsigned int len,
 169                                        u_int8_t protocol)
 170 {
 171         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 172         __wsum hsum;
 173         __sum16 csum = 0;
 174
 175         switch (skb->ip_summed) {
 176         case CHECKSUM_COMPLETE:
 177                 if (len == skb->len - dataoff)
 178                         return nf_ip6_checksum(skb, hook, dataoff, protocol);
 179                 /* fall through */
 180         case CHECKSUM_NONE:
 181                 hsum = skb_checksum(skb, 0, dataoff, 0);
 182                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
 183                                                          &ip6h->daddr,
 184                                                          skb->len - dataoff,
 185                                                          protocol,
 186                                                          csum_sub(0, hsum)));
 187                 skb->ip_summed = CHECKSUM_NONE;
 188                 return __skb_checksum_complete_head(skb, dataoff + len);
 189         }
 190         return csum;
 191 };
 192
 193 static const struct nf_ipv6_ops ipv6ops = {
 194         .chk_addr       = ipv6_chk_addr,
 195         .route_input    = ip6_route_input,
 196         .fragment       = ip6_fragment
 197 };
 198
 199 static const struct nf_afinfo nf_ip6_afinfo = {
 200         .family                 = AF_INET6,
 201         .checksum               = nf_ip6_checksum,
 202         .checksum_partial       = nf_ip6_checksum_partial,
 203         .route                  = nf_ip6_route,
 204         .saveroute              = nf_ip6_saveroute,
 205         .reroute                = nf_ip6_reroute,
 206         .route_key_size         = sizeof(struct ip6_rt_info),
 207 };
 208
 209 int __init ipv6_netfilter_init(void)
 210 {
 211         RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
 212         return nf_register_afinfo(&nf_ip6_afinfo);
 213 }
 214
 215 /* This can be called from inet6_init() on errors, so it cannot
 216  * be marked __exit. -DaveM
 217  */
 218 void ipv6_netfilter_fini(void)
 219 {
 220         RCU_INIT_POINTER(nf_ipv6_ops, NULL);
 221         nf_unregister_afinfo(&nf_ip6_afinfo);
 222 }