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