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         int strict = (ipv6_addr_type(&iph->daddr) &
  28                       (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
  29         struct flowi6 fl6 = {
  30                 .flowi6_oif = sk && sk->sk_bound_dev_if ? sk->sk_bound_dev_if :
  31                         strict ? skb_dst(skb)->dev->ifindex : 0,
  32                 .flowi6_mark = skb->mark,
  33                 .flowi6_uid = sock_net_uid(net, sk),
  34                 .daddr = iph->daddr,
  35                 .saddr = iph->saddr,
  36         };
  37         int err;
  38
  39         dst = ip6_route_output(net, sk, &fl6);
  40         err = dst->error;
  41         if (err) {
  42                 IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  43                 net_dbg_ratelimited("ip6_route_me_harder: No more route\n");
  44                 dst_release(dst);
  45                 return err;
  46         }
  47
  48         /* Drop old route. */
  49         skb_dst_drop(skb);
  50
  51         skb_dst_set(skb, dst);
  52
  53 #ifdef CONFIG_XFRM
  54         if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
  55             xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
  56                 skb_dst_set(skb, NULL);
  57                 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
  58                 if (IS_ERR(dst))
  59                         return PTR_ERR(dst);
  60                 skb_dst_set(skb, dst);
  61         }
  62 #endif
  63
  64         /* Change in oif may mean change in hh_len. */
  65         hh_len = skb_dst(skb)->dev->hard_header_len;
  66         if (skb_headroom(skb) < hh_len &&
  67             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  68                              0, GFP_ATOMIC))
  69                 return -ENOMEM;
  70
  71         return 0;
  72 }
  73 EXPORT_SYMBOL(ip6_route_me_harder);
  74
  75 /*
  76  * Extra routing may needed on local out, as the QUEUE target never
  77  * returns control to the table.
  78  */
  79
  80 struct ip6_rt_info {
  81         struct in6_addr daddr;
  82         struct in6_addr saddr;
  83         u_int32_t mark;
  84 };
  85
  86 static void nf_ip6_saveroute(const struct sk_buff *skb,
  87                              struct nf_queue_entry *entry)
  88 {
  89         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  90
  91         if (entry->state.hook == NF_INET_LOCAL_OUT) {
  92                 const struct ipv6hdr *iph = ipv6_hdr(skb);
  93
  94                 rt_info->daddr = iph->daddr;
  95                 rt_info->saddr = iph->saddr;
  96                 rt_info->mark = skb->mark;
  97         }
  98 }
  99
 100 static int nf_ip6_reroute(struct net *net, struct sk_buff *skb,
 101                           const struct nf_queue_entry *entry)
 102 {
 103         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
 104
 105         if (entry->state.hook == NF_INET_LOCAL_OUT) {
 106                 const struct ipv6hdr *iph = ipv6_hdr(skb);
 107                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
 108                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
 109                     skb->mark != rt_info->mark)
 110                         return ip6_route_me_harder(net, skb);
 111         }
 112         return 0;
 113 }
 114
 115 static int nf_ip6_route(struct net *net, struct dst_entry **dst,
 116                         struct flowi *fl, bool strict)
 117 {
 118         static const struct ipv6_pinfo fake_pinfo;
 119         static const struct inet_sock fake_sk = {
 120                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
 121                 .sk.sk_bound_dev_if = 1,
 122                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
 123         };
 124         const void *sk = strict ? &fake_sk : NULL;
 125         struct dst_entry *result;
 126         int err;
 127
 128         result = ip6_route_output(net, sk, &fl->u.ip6);
 129         err = result->error;
 130         if (err)
 131                 dst_release(result);
 132         else
 133                 *dst = result;
 134         return err;
 135 }
 136
 137 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
 138                              unsigned int dataoff, u_int8_t protocol)
 139 {
 140         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 141         __sum16 csum = 0;
 142
 143         switch (skb->ip_summed) {
 144         case CHECKSUM_COMPLETE:
 145                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 146                         break;
 147                 if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 148                                      skb->len - dataoff, protocol,
 149                                      csum_sub(skb->csum,
 150                                               skb_checksum(skb, 0,
 151                                                            dataoff, 0)))) {
 152                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 153                         break;
 154                 }
 155                 /* fall through */
 156         case CHECKSUM_NONE:
 157                 skb->csum = ~csum_unfold(
 158                                 csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 159                                              skb->len - dataoff,
 160                                              protocol,
 161                                              csum_sub(0,
 162                                                       skb_checksum(skb, 0,
 163                                                                    dataoff, 0))));
 164                 csum = __skb_checksum_complete(skb);
 165         }
 166         return csum;
 167 }
 168 EXPORT_SYMBOL(nf_ip6_checksum);
 169
 170 static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
 171                                        unsigned int dataoff, unsigned int len,
 172                                        u_int8_t protocol)
 173 {
 174         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 175         __wsum hsum;
 176         __sum16 csum = 0;
 177
 178         switch (skb->ip_summed) {
 179         case CHECKSUM_COMPLETE:
 180                 if (len == skb->len - dataoff)
 181                         return nf_ip6_checksum(skb, hook, dataoff, protocol);
 182                 /* fall through */
 183         case CHECKSUM_NONE:
 184                 hsum = skb_checksum(skb, 0, dataoff, 0);
 185                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
 186                                                          &ip6h->daddr,
 187                                                          skb->len - dataoff,
 188                                                          protocol,
 189                                                          csum_sub(0, hsum)));
 190                 skb->ip_summed = CHECKSUM_NONE;
 191                 return __skb_checksum_complete_head(skb, dataoff + len);
 192         }
 193         return csum;
 194 };
 195
 196 static const struct nf_ipv6_ops ipv6ops = {
 197         .chk_addr       = ipv6_chk_addr,
 198         .route_input    = ip6_route_input,
 199         .fragment       = ip6_fragment
 200 };
 201
 202 static const struct nf_afinfo nf_ip6_afinfo = {
 203         .family                 = AF_INET6,
 204         .checksum               = nf_ip6_checksum,
 205         .checksum_partial       = nf_ip6_checksum_partial,
 206         .route                  = nf_ip6_route,
 207         .saveroute              = nf_ip6_saveroute,
 208         .reroute                = nf_ip6_reroute,
 209         .route_key_size         = sizeof(struct ip6_rt_info),
 210 };
 211
 212 int __init ipv6_netfilter_init(void)
 213 {
 214         RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
 215         return nf_register_afinfo(&nf_ip6_afinfo);
 216 }
 217
 218 /* This can be called from inet6_init() on errors, so it cannot
 219  * be marked __exit. -DaveM
 220  */
 221 void ipv6_netfilter_fini(void)
 222 {
 223         RCU_INIT_POINTER(nf_ipv6_ops, NULL);
 224         nf_unregister_afinfo(&nf_ip6_afinfo);
 225 }