329 lines
8.4 KiB
C
329 lines
8.4 KiB
C
/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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* (C) 2011 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv4.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/ip.h>
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#include <net/ip.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_nat_core.h>
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#include <net/netfilter/nf_nat_l3proto.h>
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static const struct xt_table nf_nat_ipv4_table = {
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.name = "nat",
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.valid_hooks = (1 << NF_INET_PRE_ROUTING) |
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(1 << NF_INET_POST_ROUTING) |
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(1 << NF_INET_LOCAL_OUT) |
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(1 << NF_INET_LOCAL_IN),
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.me = THIS_MODULE,
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.af = NFPROTO_IPV4,
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};
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static unsigned int alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
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{
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/* Force range to this IP; let proto decide mapping for
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* per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
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*/
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struct nf_nat_range range;
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range.flags = 0;
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pr_debug("Allocating NULL binding for %p (%pI4)\n", ct,
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HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
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&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip :
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&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
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return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
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}
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static unsigned int nf_nat_rule_find(struct sk_buff *skb, unsigned int hooknum,
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const struct net_device *in,
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const struct net_device *out,
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struct nf_conn *ct)
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{
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struct net *net = nf_ct_net(ct);
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unsigned int ret;
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ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
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if (ret == NF_ACCEPT) {
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if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
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ret = alloc_null_binding(ct, hooknum);
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}
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return ret;
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}
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static unsigned int
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nf_nat_ipv4_fn(const struct nf_hook_ops *ops,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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struct nf_conn_nat *nat;
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/* maniptype == SRC for postrouting. */
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enum nf_nat_manip_type maniptype = HOOK2MANIP(ops->hooknum);
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/* We never see fragments: conntrack defrags on pre-routing
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* and local-out, and nf_nat_out protects post-routing.
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*/
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NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));
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ct = nf_ct_get(skb, &ctinfo);
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/* Can't track? It's not due to stress, or conntrack would
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* have dropped it. Hence it's the user's responsibilty to
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* packet filter it out, or implement conntrack/NAT for that
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* protocol. 8) --RR
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*/
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if (!ct)
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return NF_ACCEPT;
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/* Don't try to NAT if this packet is not conntracked */
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if (nf_ct_is_untracked(ct))
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return NF_ACCEPT;
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nat = nf_ct_nat_ext_add(ct);
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if (nat == NULL)
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return NF_ACCEPT;
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switch (ctinfo) {
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case IP_CT_RELATED:
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case IP_CT_RELATED_REPLY:
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if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
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if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
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ops->hooknum))
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return NF_DROP;
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else
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return NF_ACCEPT;
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}
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/* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
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case IP_CT_NEW:
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/* Seen it before? This can happen for loopback, retrans,
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* or local packets.
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*/
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if (!nf_nat_initialized(ct, maniptype)) {
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unsigned int ret;
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ret = nf_nat_rule_find(skb, ops->hooknum, in, out, ct);
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if (ret != NF_ACCEPT)
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return ret;
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} else {
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pr_debug("Already setup manip %s for ct %p\n",
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maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
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ct);
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if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat, out))
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goto oif_changed;
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}
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break;
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default:
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/* ESTABLISHED */
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NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
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ctinfo == IP_CT_ESTABLISHED_REPLY);
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if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat, out))
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goto oif_changed;
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}
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return nf_nat_packet(ct, ctinfo, ops->hooknum, skb);
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oif_changed:
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nf_ct_kill_acct(ct, ctinfo, skb);
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return NF_DROP;
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}
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static unsigned int
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nf_nat_ipv4_in(const struct nf_hook_ops *ops,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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unsigned int ret;
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__be32 daddr = ip_hdr(skb)->daddr;
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ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
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if (ret != NF_DROP && ret != NF_STOLEN &&
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daddr != ip_hdr(skb)->daddr)
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skb_dst_drop(skb);
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return ret;
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}
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static unsigned int
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nf_nat_ipv4_out(const struct nf_hook_ops *ops,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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#ifdef CONFIG_XFRM
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const struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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int err;
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#endif
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unsigned int ret;
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/* root is playing with raw sockets. */
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if (skb->len < sizeof(struct iphdr) ||
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ip_hdrlen(skb) < sizeof(struct iphdr))
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return NF_ACCEPT;
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ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
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#ifdef CONFIG_XFRM
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if (ret != NF_DROP && ret != NF_STOLEN &&
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!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
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(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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if ((ct->tuplehash[dir].tuple.src.u3.ip !=
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ct->tuplehash[!dir].tuple.dst.u3.ip) ||
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(ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
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ct->tuplehash[dir].tuple.src.u.all !=
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ct->tuplehash[!dir].tuple.dst.u.all)) {
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err = nf_xfrm_me_harder(skb, AF_INET);
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if (err < 0)
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ret = NF_DROP_ERR(err);
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}
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}
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#endif
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return ret;
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}
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static unsigned int
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nf_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
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struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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int (*okfn)(struct sk_buff *))
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{
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const struct nf_conn *ct;
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enum ip_conntrack_info ctinfo;
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unsigned int ret;
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int err;
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/* root is playing with raw sockets. */
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if (skb->len < sizeof(struct iphdr) ||
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ip_hdrlen(skb) < sizeof(struct iphdr))
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return NF_ACCEPT;
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ret = nf_nat_ipv4_fn(ops, skb, in, out, okfn);
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if (ret != NF_DROP && ret != NF_STOLEN &&
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(ct = nf_ct_get(skb, &ctinfo)) != NULL) {
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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if (ct->tuplehash[dir].tuple.dst.u3.ip !=
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ct->tuplehash[!dir].tuple.src.u3.ip) {
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err = ip_route_me_harder(skb, RTN_UNSPEC);
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if (err < 0)
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ret = NF_DROP_ERR(err);
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}
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#ifdef CONFIG_XFRM
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else if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
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ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
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ct->tuplehash[dir].tuple.dst.u.all !=
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ct->tuplehash[!dir].tuple.src.u.all) {
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err = nf_xfrm_me_harder(skb, AF_INET);
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if (err < 0)
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ret = NF_DROP_ERR(err);
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}
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#endif
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}
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return ret;
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}
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static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
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/* Before packet filtering, change destination */
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{
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.hook = nf_nat_ipv4_in,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_PRE_ROUTING,
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.priority = NF_IP_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = nf_nat_ipv4_out,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_POST_ROUTING,
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.priority = NF_IP_PRI_NAT_SRC,
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},
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/* Before packet filtering, change destination */
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{
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.hook = nf_nat_ipv4_local_fn,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_LOCAL_OUT,
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.priority = NF_IP_PRI_NAT_DST,
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},
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/* After packet filtering, change source */
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{
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.hook = nf_nat_ipv4_fn,
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.owner = THIS_MODULE,
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.pf = NFPROTO_IPV4,
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.hooknum = NF_INET_LOCAL_IN,
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.priority = NF_IP_PRI_NAT_SRC,
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},
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};
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static int __net_init iptable_nat_net_init(struct net *net)
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{
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struct ipt_replace *repl;
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repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
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if (repl == NULL)
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return -ENOMEM;
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net->ipv4.nat_table = ipt_register_table(net, &nf_nat_ipv4_table, repl);
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kfree(repl);
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return PTR_ERR_OR_ZERO(net->ipv4.nat_table);
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}
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static void __net_exit iptable_nat_net_exit(struct net *net)
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{
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ipt_unregister_table(net, net->ipv4.nat_table);
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}
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static struct pernet_operations iptable_nat_net_ops = {
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.init = iptable_nat_net_init,
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.exit = iptable_nat_net_exit,
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};
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static int __init iptable_nat_init(void)
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{
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int err;
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err = register_pernet_subsys(&iptable_nat_net_ops);
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if (err < 0)
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goto err1;
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err = nf_register_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
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if (err < 0)
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goto err2;
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return 0;
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err2:
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unregister_pernet_subsys(&iptable_nat_net_ops);
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err1:
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return err;
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}
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static void __exit iptable_nat_exit(void)
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{
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nf_unregister_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
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unregister_pernet_subsys(&iptable_nat_net_ops);
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}
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module_init(iptable_nat_init);
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module_exit(iptable_nat_exit);
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MODULE_LICENSE("GPL");
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