netfilter: ipv6: add IPv6 NAT support

Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 321 insertions, 0 deletions

diff --git a/net/ipv6/netfilter/ip6table_nat.c b/net/ipv6/netfilter/ip6table_nat.c
new file mode 100644
index 00000000000..e418bd6350a
--- /dev/null
+++ b/net/ipv6/netfilter/ip6table_nat.c
@@ -0,0 +1,321 @@
+/*
+ * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Based on Rusty Russell's IPv4 NAT code. Development of IPv6 NAT
+ * funded by Astaro.
+ */
+
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv6.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <linux/ipv6.h>
+#include <net/ipv6.h>
+
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_core.h>
+#include <net/netfilter/nf_nat_l3proto.h>
+
+static const struct xt_table nf_nat_ipv6_table = {
+        .name           = "nat",
+        .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
+                          (1 << NF_INET_POST_ROUTING) |
+                          (1 << NF_INET_LOCAL_OUT) |
+                          (1 << NF_INET_LOCAL_IN),
+        .me             = THIS_MODULE,
+        .af             = NFPROTO_IPV6,
+};
+
+static unsigned int alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
+{
+        /* Force range to this IP; let proto decide mapping for
+         * per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
+         */
+        struct nf_nat_range range;
+
+        range.flags = 0;
+        pr_debug("Allocating NULL binding for %p (%pI6)\n", ct,
+                 HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
+                 &ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip6 :
+                 &ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip6);
+
+        return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
+}
+
+static unsigned int nf_nat_rule_find(struct sk_buff *skb, unsigned int hooknum,
+                                     const struct net_device *in,
+                                     const struct net_device *out,
+                                     struct nf_conn *ct)
+{
+        struct net *net = nf_ct_net(ct);
+        unsigned int ret;
+
+        ret = ip6t_do_table(skb, hooknum, in, out, net->ipv6.ip6table_nat);
+        if (ret == NF_ACCEPT) {
+                if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
+                        ret = alloc_null_binding(ct, hooknum);
+        }
+        return ret;
+}
+
+static unsigned int
+nf_nat_ipv6_fn(unsigned int hooknum,
+               struct sk_buff *skb,
+               const struct net_device *in,
+               const struct net_device *out,
+               int (*okfn)(struct sk_buff *))
+{
+        struct nf_conn *ct;
+        enum ip_conntrack_info ctinfo;
+        struct nf_conn_nat *nat;
+        enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
+        __be16 frag_off;
+        int hdrlen;
+        u8 nexthdr;
+
+        ct = nf_ct_get(skb, &ctinfo);
+        /* Can't track?  It's not due to stress, or conntrack would
+         * have dropped it.  Hence it's the user's responsibilty to
+         * packet filter it out, or implement conntrack/NAT for that
+         * protocol. 8) --RR
+         */
+        if (!ct)
+                return NF_ACCEPT;
+
+        /* Don't try to NAT if this packet is not conntracked */
+        if (nf_ct_is_untracked(ct))
+                return NF_ACCEPT;
+
+        nat = nfct_nat(ct);
+        if (!nat) {
+                /* NAT module was loaded late. */
+                if (nf_ct_is_confirmed(ct))
+                        return NF_ACCEPT;
+                nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
+                if (nat == NULL) {
+                        pr_debug("failed to add NAT extension\n");
+                        return NF_ACCEPT;
+                }
+        }
+
+        switch (ctinfo) {
+        case IP_CT_RELATED:
+        case IP_CT_RELATED_REPLY:
+                nexthdr = ipv6_hdr(skb)->nexthdr;
+                hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
+                                          &nexthdr, &frag_off);
+
+                if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
+                        if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
+                                                             hooknum, hdrlen))
+                                return NF_DROP;
+                        else
+                                return NF_ACCEPT;
+                }
+                /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
+        case IP_CT_NEW:
+                /* Seen it before?  This can happen for loopback, retrans,
+                 * or local packets.
+                 */
+                if (!nf_nat_initialized(ct, maniptype)) {
+                        unsigned int ret;
+
+                        ret = nf_nat_rule_find(skb, hooknum, in, out, ct);
+                        if (ret != NF_ACCEPT)
+                                return ret;
+                } else
+                        pr_debug("Already setup manip %s for ct %p\n",
+                                 maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
+                                 ct);
+                break;
+
+        default:
+                /* ESTABLISHED */
+                NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
+                             ctinfo == IP_CT_ESTABLISHED_REPLY);
+        }
+
+        return nf_nat_packet(ct, ctinfo, hooknum, skb);
+}
+
+static unsigned int
+nf_nat_ipv6_in(unsigned int hooknum,
+               struct sk_buff *skb,
+               const struct net_device *in,
+               const struct net_device *out,
+               int (*okfn)(struct sk_buff *))
+{
+        unsigned int ret;
+        struct in6_addr daddr = ipv6_hdr(skb)->daddr;
+
+        ret = nf_nat_ipv6_fn(hooknum, skb, in, out, okfn);
+        if (ret != NF_DROP && ret != NF_STOLEN &&
+            ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
+                skb_dst_drop(skb);
+
+        return ret;
+}
+
+static unsigned int
+nf_nat_ipv6_out(unsigned int hooknum,
+                struct sk_buff *skb,
+                const struct net_device *in,
+                const struct net_device *out,
+                int (*okfn)(struct sk_buff *))
+{
+#ifdef CONFIG_XFRM
+        const struct nf_conn *ct;
+        enum ip_conntrack_info ctinfo;
+#endif
+        unsigned int ret;
+
+        /* root is playing with raw sockets. */
+        if (skb->len < sizeof(struct ipv6hdr))
+                return NF_ACCEPT;
+
+        ret = nf_nat_ipv6_fn(hooknum, skb, in, out, okfn);
+#ifdef CONFIG_XFRM
+        if (ret != NF_DROP && ret != NF_STOLEN &&
+            !(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
+            (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
+                enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+
+                if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
+                                      &ct->tuplehash[!dir].tuple.dst.u3) ||
+                    (ct->tuplehash[dir].tuple.src.u.all !=
+                     ct->tuplehash[!dir].tuple.dst.u.all))
+                        if (nf_xfrm_me_harder(skb, AF_INET6) < 0)
+                                ret = NF_DROP;
+        }
+#endif
+        return ret;
+}
+
+static unsigned int
+nf_nat_ipv6_local_fn(unsigned int hooknum,
+                     struct sk_buff *skb,
+                     const struct net_device *in,
+                     const struct net_device *out,
+                     int (*okfn)(struct sk_buff *))
+{
+        const struct nf_conn *ct;
+        enum ip_conntrack_info ctinfo;
+        unsigned int ret;
+
+        /* root is playing with raw sockets. */
+        if (skb->len < sizeof(struct ipv6hdr))
+                return NF_ACCEPT;
+
+        ret = nf_nat_ipv6_fn(hooknum, skb, in, out, okfn);
+        if (ret != NF_DROP && ret != NF_STOLEN &&
+            (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
+                enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+
+                if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
+                                      &ct->tuplehash[!dir].tuple.src.u3)) {
+                        if (ip6_route_me_harder(skb))
+                                ret = NF_DROP;
+                }
+#ifdef CONFIG_XFRM
+                else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
+                         ct->tuplehash[dir].tuple.dst.u.all !=
+                         ct->tuplehash[!dir].tuple.src.u.all)
+                        if (nf_xfrm_me_harder(skb, AF_INET6))
+                                ret = NF_DROP;
+#endif
+        }
+        return ret;
+}
+
+static struct nf_hook_ops nf_nat_ipv6_ops[] __read_mostly = {
+        /* Before packet filtering, change destination */
+        {
+                .hook           = nf_nat_ipv6_in,
+                .owner          = THIS_MODULE,
+                .pf             = NFPROTO_IPV6,
+                .hooknum        = NF_INET_PRE_ROUTING,
+                .priority       = NF_IP6_PRI_NAT_DST,
+        },
+        /* After packet filtering, change source */
+        {
+                .hook           = nf_nat_ipv6_out,
+                .owner          = THIS_MODULE,
+                .pf             = NFPROTO_IPV6,
+                .hooknum        = NF_INET_POST_ROUTING,
+                .priority       = NF_IP6_PRI_NAT_SRC,
+        },
+        /* Before packet filtering, change destination */
+        {
+                .hook           = nf_nat_ipv6_local_fn,
+                .owner          = THIS_MODULE,
+                .pf             = NFPROTO_IPV6,
+                .hooknum        = NF_INET_LOCAL_OUT,
+                .priority       = NF_IP6_PRI_NAT_DST,
+        },
+        /* After packet filtering, change source */
+        {
+                .hook           = nf_nat_ipv6_fn,
+                .owner          = THIS_MODULE,
+                .pf             = NFPROTO_IPV6,
+                .hooknum        = NF_INET_LOCAL_IN,
+                .priority       = NF_IP6_PRI_NAT_SRC,
+        },
+};
+
+static int __net_init ip6table_nat_net_init(struct net *net)
+{
+        struct ip6t_replace *repl;
+
+        repl = ip6t_alloc_initial_table(&nf_nat_ipv6_table);
+        if (repl == NULL)
+                return -ENOMEM;
+        net->ipv6.ip6table_nat = ip6t_register_table(net, &nf_nat_ipv6_table, repl);
+        kfree(repl);
+        if (IS_ERR(net->ipv6.ip6table_nat))
+                return PTR_ERR(net->ipv6.ip6table_nat);
+        return 0;
+}
+
+static void __net_exit ip6table_nat_net_exit(struct net *net)
+{
+        ip6t_unregister_table(net, net->ipv6.ip6table_nat);
+}
+
+static struct pernet_operations ip6table_nat_net_ops = {
+        .init   = ip6table_nat_net_init,
+        .exit   = ip6table_nat_net_exit,
+};
+
+static int __init ip6table_nat_init(void)
+{
+        int err;
+
+        err = register_pernet_subsys(&ip6table_nat_net_ops);
+        if (err < 0)
+                goto err1;
+
+        err = nf_register_hooks(nf_nat_ipv6_ops, ARRAY_SIZE(nf_nat_ipv6_ops));
+        if (err < 0)
+                goto err2;
+        return 0;
+
+err2:
+        unregister_pernet_subsys(&ip6table_nat_net_ops);
+err1:
+        return err;
+}
+
+static void __exit ip6table_nat_exit(void)
+{
+        nf_unregister_hooks(nf_nat_ipv6_ops, ARRAY_SIZE(nf_nat_ipv6_ops));
+        unregister_pernet_subsys(&ip6table_nat_net_ops);
+}
+
+module_init(ip6table_nat_init);
+module_exit(ip6table_nat_exit);
+
+MODULE_LICENSE("GPL");