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 sk_buff *skb)
  22 {
  23         struct net *net = dev_net(skb_dst(skb)->dev);
  24         const struct ipv6hdr *iph = ipv6_hdr(skb);
  25         unsigned int hh_len;
  26         struct dst_entry *dst;
  27         struct flowi6 fl6 = {
  28                 .flowi6_oif = skb->sk ? skb->sk->sk_bound_dev_if : 0,
  29                 .flowi6_mark = skb->mark,
  30                 .daddr = iph->daddr,
  31                 .saddr = iph->saddr,
  32         };
  33
  34         dst = ip6_route_output(net, skb->sk, &fl6);
  35         if (dst->error) {
  36                 IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  37                 LIMIT_NETDEBUG(KERN_DEBUG "ip6_route_me_harder: No more route.\n");
  38                 dst_release(dst);
  39                 return dst->error;
  40         }
  41
  42         /* Drop old route. */
  43         skb_dst_drop(skb);
  44
  45         skb_dst_set(skb, dst);
  46
  47 #ifdef CONFIG_XFRM
  48         if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
  49             xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
  50                 skb_dst_set(skb, NULL);
  51                 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), skb->sk, 0);
  52                 if (IS_ERR(dst))
  53                         return PTR_ERR(dst);
  54                 skb_dst_set(skb, dst);
  55         }
  56 #endif
  57
  58         /* Change in oif may mean change in hh_len. */
  59         hh_len = skb_dst(skb)->dev->hard_header_len;
  60         if (skb_headroom(skb) < hh_len &&
  61             pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  62                              0, GFP_ATOMIC))
  63                 return -ENOMEM;
  64
  65         return 0;
  66 }
  67 EXPORT_SYMBOL(ip6_route_me_harder);
  68
  69 /*
  70  * Extra routing may needed on local out, as the QUEUE target never
  71  * returns control to the table.
  72  */
  73
  74 struct ip6_rt_info {
  75         struct in6_addr daddr;
  76         struct in6_addr saddr;
  77         u_int32_t mark;
  78 };
  79
  80 static void nf_ip6_saveroute(const struct sk_buff *skb,
  81                              struct nf_queue_entry *entry)
  82 {
  83         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  84
  85         if (entry->hook == NF_INET_LOCAL_OUT) {
  86                 const struct ipv6hdr *iph = ipv6_hdr(skb);
  87
  88                 rt_info->daddr = iph->daddr;
  89                 rt_info->saddr = iph->saddr;
  90                 rt_info->mark = skb->mark;
  91         }
  92 }
  93
  94 static int nf_ip6_reroute(struct sk_buff *skb,
  95                           const struct nf_queue_entry *entry)
  96 {
  97         struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  98
  99         if (entry->hook == NF_INET_LOCAL_OUT) {
 100                 const struct ipv6hdr *iph = ipv6_hdr(skb);
 101                 if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
 102                     !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
 103                     skb->mark != rt_info->mark)
 104                         return ip6_route_me_harder(skb);
 105         }
 106         return 0;
 107 }
 108
 109 static int nf_ip6_route(struct net *net, struct dst_entry **dst,
 110                         struct flowi *fl, bool strict)
 111 {
 112         static const struct ipv6_pinfo fake_pinfo;
 113         static const struct inet_sock fake_sk = {
 114                 /* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
 115                 .sk.sk_bound_dev_if = 1,
 116                 .pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
 117         };
 118         const void *sk = strict ? &fake_sk : NULL;
 119         struct dst_entry *result;
 120         int err;
 121
 122         result = ip6_route_output(net, sk, &fl->u.ip6);
 123         err = result->error;
 124         if (err)
 125                 dst_release(result);
 126         else
 127                 *dst = result;
 128         return err;
 129 }
 130
 131 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
 132                              unsigned int dataoff, u_int8_t protocol)
 133 {
 134         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 135         __sum16 csum = 0;
 136
 137         switch (skb->ip_summed) {
 138         case CHECKSUM_COMPLETE:
 139                 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
 140                         break;
 141                 if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 142                                      skb->len - dataoff, protocol,
 143                                      csum_sub(skb->csum,
 144                                               skb_checksum(skb, 0,
 145                                                            dataoff, 0)))) {
 146                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 147                         break;
 148                 }
 149                 /* fall through */
 150         case CHECKSUM_NONE:
 151                 skb->csum = ~csum_unfold(
 152                                 csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
 153                                              skb->len - dataoff,
 154                                              protocol,
 155                                              csum_sub(0,
 156                                                       skb_checksum(skb, 0,
 157                                                                    dataoff, 0))));
 158                 csum = __skb_checksum_complete(skb);
 159         }
 160         return csum;
 161 }
 162 EXPORT_SYMBOL(nf_ip6_checksum);
 163
 164 static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
 165                                        unsigned int dataoff, unsigned int len,
 166                                        u_int8_t protocol)
 167 {
 168         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 169         __wsum hsum;
 170         __sum16 csum = 0;
 171
 172         switch (skb->ip_summed) {
 173         case CHECKSUM_COMPLETE:
 174                 if (len == skb->len - dataoff)
 175                         return nf_ip6_checksum(skb, hook, dataoff, protocol);
 176                 /* fall through */
 177         case CHECKSUM_NONE:
 178                 hsum = skb_checksum(skb, 0, dataoff, 0);
 179                 skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
 180                                                          &ip6h->daddr,
 181                                                          skb->len - dataoff,
 182                                                          protocol,
 183                                                          csum_sub(0, hsum)));
 184                 skb->ip_summed = CHECKSUM_NONE;
 185                 return __skb_checksum_complete_head(skb, dataoff + len);
 186         }
 187         return csum;
 188 };
 189
 190 static const struct nf_ipv6_ops ipv6ops = {
 191         .chk_addr       = ipv6_chk_addr,
 192 };
 193
 194 static const struct nf_afinfo nf_ip6_afinfo = {
 195         .family                 = AF_INET6,
 196         .checksum               = nf_ip6_checksum,
 197         .checksum_partial       = nf_ip6_checksum_partial,
 198         .route                  = nf_ip6_route,
 199         .saveroute              = nf_ip6_saveroute,
 200         .reroute                = nf_ip6_reroute,
 201         .route_key_size         = sizeof(struct ip6_rt_info),
 202 };
 203
 204 int __init ipv6_netfilter_init(void)
 205 {
 206         RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
 207         return nf_register_afinfo(&nf_ip6_afinfo);
 208 }
 209
 210 /* This can be called from inet6_init() on errors, so it cannot
 211  * be marked __exit. -DaveM
 212  */
 213 void ipv6_netfilter_fini(void)
 214 {
 215         RCU_INIT_POINTER(nf_ipv6_ops, NULL);
 216         nf_unregister_afinfo(&nf_ip6_afinfo);
 217 }