net/ipv6/netfilter/nf_nat_l3proto_ipv6.c

   1 /*
   2  * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Development of IPv6 NAT funded by Astaro.
   9  */
  10 #include <linux/types.h>
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ipv6.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv6.h>
  16 #include <net/secure_seq.h>
  17 #include <net/checksum.h>
  18 #include <net/ip6_checksum.h>
  19 #include <net/ip6_route.h>
  20 #include <net/ipv6.h>
  21
  22 #include <net/netfilter/nf_conntrack_core.h>
  23 #include <net/netfilter/nf_conntrack.h>
  24 #include <net/netfilter/nf_nat_core.h>
  25 #include <net/netfilter/nf_nat_l3proto.h>
  26 #include <net/netfilter/nf_nat_l4proto.h>
  27
  28 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6;
  29
  30 #ifdef CONFIG_XFRM
  31 static void nf_nat_ipv6_decode_session(struct sk_buff *skb,
  32                                        const struct nf_conn *ct,
  33                                        enum ip_conntrack_dir dir,
  34                                        unsigned long statusbit,
  35                                        struct flowi *fl)
  36 {
  37         const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
  38         struct flowi6 *fl6 = &fl->u.ip6;
  39
  40         if (ct->status & statusbit) {
  41                 fl6->daddr = t->dst.u3.in6;
  42                 if (t->dst.protonum == IPPROTO_TCP ||
  43                     t->dst.protonum == IPPROTO_UDP ||
  44                     t->dst.protonum == IPPROTO_UDPLITE ||
  45                     t->dst.protonum == IPPROTO_DCCP ||
  46                     t->dst.protonum == IPPROTO_SCTP)
  47                         fl6->fl6_dport = t->dst.u.all;
  48         }
  49
  50         statusbit ^= IPS_NAT_MASK;
  51
  52         if (ct->status & statusbit) {
  53                 fl6->saddr = t->src.u3.in6;
  54                 if (t->dst.protonum == IPPROTO_TCP ||
  55                     t->dst.protonum == IPPROTO_UDP ||
  56                     t->dst.protonum == IPPROTO_UDPLITE ||
  57                     t->dst.protonum == IPPROTO_DCCP ||
  58                     t->dst.protonum == IPPROTO_SCTP)
  59                         fl6->fl6_sport = t->src.u.all;
  60         }
  61 }
  62 #endif
  63
  64 static bool nf_nat_ipv6_in_range(const struct nf_conntrack_tuple *t,
  65                                  const struct nf_nat_range *range)
  66 {
  67         return ipv6_addr_cmp(&t->src.u3.in6, &range->min_addr.in6) >= 0 &&
  68                ipv6_addr_cmp(&t->src.u3.in6, &range->max_addr.in6) <= 0;
  69 }
  70
  71 static u32 nf_nat_ipv6_secure_port(const struct nf_conntrack_tuple *t,
  72                                    __be16 dport)
  73 {
  74         return secure_ipv6_port_ephemeral(t->src.u3.ip6, t->dst.u3.ip6, dport);
  75 }
  76
  77 static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
  78                                   unsigned int iphdroff,
  79                                   const struct nf_nat_l4proto *l4proto,
  80                                   const struct nf_conntrack_tuple *target,
  81                                   enum nf_nat_manip_type maniptype)
  82 {
  83         struct ipv6hdr *ipv6h;
  84         __be16 frag_off;
  85         int hdroff;
  86         u8 nexthdr;
  87
  88         if (!skb_make_writable(skb, iphdroff + sizeof(*ipv6h)))
  89                 return false;
  90
  91         ipv6h = (void *)skb->data + iphdroff;
  92         nexthdr = ipv6h->nexthdr;
  93         hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
  94                                   &nexthdr, &frag_off);
  95         if (hdroff < 0)
  96                 goto manip_addr;
  97
  98         if ((frag_off & htons(~0x7)) == 0 &&
  99             !l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
 100                                 target, maniptype))
 101                 return false;
 102 manip_addr:
 103         if (maniptype == NF_NAT_MANIP_SRC)
 104                 ipv6h->saddr = target->src.u3.in6;
 105         else
 106                 ipv6h->daddr = target->dst.u3.in6;
 107
 108         return true;
 109 }
 110
 111 static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
 112                                     unsigned int iphdroff, __sum16 *check,
 113                                     const struct nf_conntrack_tuple *t,
 114                                     enum nf_nat_manip_type maniptype)
 115 {
 116         const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
 117         const struct in6_addr *oldip, *newip;
 118
 119         if (maniptype == NF_NAT_MANIP_SRC) {
 120                 oldip = &ipv6h->saddr;
 121                 newip = &t->src.u3.in6;
 122         } else {
 123                 oldip = &ipv6h->daddr;
 124                 newip = &t->dst.u3.in6;
 125         }
 126         inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
 127                                   newip->s6_addr32, 1);
 128 }
 129
 130 static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
 131                                     u8 proto, void *data, __sum16 *check,
 132                                     int datalen, int oldlen)
 133 {
 134         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 135         struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 136
 137         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 138                 if (!(rt->rt6i_flags & RTF_LOCAL) &&
 139                     (!skb->dev || skb->dev->features & NETIF_F_V6_CSUM)) {
 140                         skb->ip_summed = CHECKSUM_PARTIAL;
 141                         skb->csum_start = skb_headroom(skb) +
 142                                           skb_network_offset(skb) +
 143                                           (data - (void *)skb->data);
 144                         skb->csum_offset = (void *)check - data;
 145                         *check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 146                                                   datalen, proto, 0);
 147                 } else {
 148                         *check = 0;
 149                         *check = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 150                                                  datalen, proto,
 151                                                  csum_partial(data, datalen,
 152                                                               0));
 153                         if (proto == IPPROTO_UDP && !*check)
 154                                 *check = CSUM_MANGLED_0;
 155                 }
 156         } else
 157                 inet_proto_csum_replace2(check, skb,
 158                                          htons(oldlen), htons(datalen), 1);
 159 }
 160
 161 static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
 162                                        struct nf_nat_range *range)
 163 {
 164         if (tb[CTA_NAT_V6_MINIP]) {
 165                 nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
 166                            sizeof(struct in6_addr));
 167                 range->flags |= NF_NAT_RANGE_MAP_IPS;
 168         }
 169
 170         if (tb[CTA_NAT_V6_MAXIP])
 171                 nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
 172                            sizeof(struct in6_addr));
 173         else
 174                 range->max_addr = range->min_addr;
 175
 176         return 0;
 177 }
 178
 179 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
 180         .l3proto                = NFPROTO_IPV6,
 181         .secure_port            = nf_nat_ipv6_secure_port,
 182         .in_range               = nf_nat_ipv6_in_range,
 183         .manip_pkt              = nf_nat_ipv6_manip_pkt,
 184         .csum_update            = nf_nat_ipv6_csum_update,
 185         .csum_recalc            = nf_nat_ipv6_csum_recalc,
 186         .nlattr_to_range        = nf_nat_ipv6_nlattr_to_range,
 187 #ifdef CONFIG_XFRM
 188         .decode_session = nf_nat_ipv6_decode_session,
 189 #endif
 190 };
 191
 192 int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 193                                     struct nf_conn *ct,
 194                                     enum ip_conntrack_info ctinfo,
 195                                     unsigned int hooknum,
 196                                     unsigned int hdrlen)
 197 {
 198         struct {
 199                 struct icmp6hdr icmp6;
 200                 struct ipv6hdr  ip6;
 201         } *inside;
 202         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 203         enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 204         const struct nf_nat_l4proto *l4proto;
 205         struct nf_conntrack_tuple target;
 206         unsigned long statusbit;
 207
 208         NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
 209
 210         if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 211                 return 0;
 212         if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
 213                 return 0;
 214
 215         inside = (void *)skb->data + hdrlen;
 216         if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
 217                 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
 218                         return 0;
 219                 if (ct->status & IPS_NAT_MASK)
 220                         return 0;
 221         }
 222
 223         if (manip == NF_NAT_MANIP_SRC)
 224                 statusbit = IPS_SRC_NAT;
 225         else
 226                 statusbit = IPS_DST_NAT;
 227
 228         /* Invert if this is reply direction */
 229         if (dir == IP_CT_DIR_REPLY)
 230                 statusbit ^= IPS_NAT_MASK;
 231
 232         if (!(ct->status & statusbit))
 233                 return 1;
 234
 235         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
 236         if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 237                                    l4proto, &ct->tuplehash[!dir].tuple, !manip))
 238                 return 0;
 239
 240         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 241                 struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 242                 inside = (void *)skb->data + hdrlen;
 243                 inside->icmp6.icmp6_cksum = 0;
 244                 inside->icmp6.icmp6_cksum =
 245                         csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 246                                         skb->len - hdrlen, IPPROTO_ICMPV6,
 247                                         csum_partial(&inside->icmp6,
 248                                                      skb->len - hdrlen, 0));
 249         }
 250
 251         nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 252         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
 253         if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 254                 return 0;
 255
 256         return 1;
 257 }
 258 EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);
 259
 260 static int __init nf_nat_l3proto_ipv6_init(void)
 261 {
 262         int err;
 263
 264         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 265         if (err < 0)
 266                 goto err1;
 267         err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
 268         if (err < 0)
 269                 goto err2;
 270         return err;
 271
 272 err2:
 273         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 274 err1:
 275         return err;
 276 }
 277
 278 static void __exit nf_nat_l3proto_ipv6_exit(void)
 279 {
 280         nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
 281         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 282 }
 283
 284 MODULE_LICENSE("GPL");
 285 MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));
 286
 287 module_init(nf_nat_l3proto_ipv6_init);
 288 module_exit(nf_nat_l3proto_ipv6_exit);