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