388 lines
10 KiB
C
388 lines
10 KiB
C
/*
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* (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/types.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/ip.h>
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#include <linux/icmp.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/secure_seq.h>
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#include <net/checksum.h>
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#include <net/route.h>
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#include <net/ip.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack.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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#include <net/netfilter/nf_nat_l4proto.h>
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static const struct nf_nat_l3proto nf_nat_l3proto_ipv4;
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#ifdef CONFIG_XFRM
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static void nf_nat_ipv4_decode_session(struct sk_buff *skb,
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const struct nf_conn *ct,
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enum ip_conntrack_dir dir,
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unsigned long statusbit,
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struct flowi *fl)
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{
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const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
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struct flowi4 *fl4 = &fl->u.ip4;
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if (ct->status & statusbit) {
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fl4->daddr = t->dst.u3.ip;
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if (t->dst.protonum == IPPROTO_TCP ||
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t->dst.protonum == IPPROTO_UDP ||
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t->dst.protonum == IPPROTO_UDPLITE ||
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t->dst.protonum == IPPROTO_DCCP ||
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t->dst.protonum == IPPROTO_SCTP)
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fl4->fl4_dport = t->dst.u.all;
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}
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statusbit ^= IPS_NAT_MASK;
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if (ct->status & statusbit) {
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fl4->saddr = t->src.u3.ip;
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if (t->dst.protonum == IPPROTO_TCP ||
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t->dst.protonum == IPPROTO_UDP ||
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t->dst.protonum == IPPROTO_UDPLITE ||
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t->dst.protonum == IPPROTO_DCCP ||
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t->dst.protonum == IPPROTO_SCTP)
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fl4->fl4_sport = t->src.u.all;
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}
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}
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#endif /* CONFIG_XFRM */
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static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
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unsigned int iphdroff,
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const struct nf_conntrack_tuple *target,
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enum nf_nat_manip_type maniptype)
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{
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struct iphdr *iph;
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unsigned int hdroff;
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if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
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return false;
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iph = (void *)skb->data + iphdroff;
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hdroff = iphdroff + iph->ihl * 4;
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if (!nf_nat_l4proto_manip_pkt(skb, &nf_nat_l3proto_ipv4, iphdroff,
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hdroff, target, maniptype))
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return false;
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iph = (void *)skb->data + iphdroff;
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if (maniptype == NF_NAT_MANIP_SRC) {
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csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
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iph->saddr = target->src.u3.ip;
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} else {
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csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
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iph->daddr = target->dst.u3.ip;
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}
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return true;
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}
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static void nf_nat_ipv4_csum_update(struct sk_buff *skb,
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unsigned int iphdroff, __sum16 *check,
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const struct nf_conntrack_tuple *t,
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enum nf_nat_manip_type maniptype)
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{
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struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
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__be32 oldip, newip;
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if (maniptype == NF_NAT_MANIP_SRC) {
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oldip = iph->saddr;
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newip = t->src.u3.ip;
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} else {
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oldip = iph->daddr;
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newip = t->dst.u3.ip;
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}
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inet_proto_csum_replace4(check, skb, oldip, newip, true);
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}
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static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb,
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u8 proto, void *data, __sum16 *check,
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int datalen, int oldlen)
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{
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if (skb->ip_summed != CHECKSUM_PARTIAL) {
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const struct iphdr *iph = ip_hdr(skb);
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skb->ip_summed = CHECKSUM_PARTIAL;
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skb->csum_start = skb_headroom(skb) + skb_network_offset(skb) +
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ip_hdrlen(skb);
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skb->csum_offset = (void *)check - data;
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*check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
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proto, 0);
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} else
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inet_proto_csum_replace2(check, skb,
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htons(oldlen), htons(datalen), true);
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}
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[],
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struct nf_nat_range2 *range)
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{
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if (tb[CTA_NAT_V4_MINIP]) {
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range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]);
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range->flags |= NF_NAT_RANGE_MAP_IPS;
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}
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if (tb[CTA_NAT_V4_MAXIP])
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range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]);
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else
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range->max_addr.ip = range->min_addr.ip;
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return 0;
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}
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#endif
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static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = {
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.l3proto = NFPROTO_IPV4,
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.manip_pkt = nf_nat_ipv4_manip_pkt,
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.csum_update = nf_nat_ipv4_csum_update,
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.csum_recalc = nf_nat_ipv4_csum_recalc,
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#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
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.nlattr_to_range = nf_nat_ipv4_nlattr_to_range,
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#endif
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#ifdef CONFIG_XFRM
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.decode_session = nf_nat_ipv4_decode_session,
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#endif
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};
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int nf_nat_icmp_reply_translation(struct sk_buff *skb,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int hooknum)
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{
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struct {
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struct icmphdr icmp;
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struct iphdr ip;
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} *inside;
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enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
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enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
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unsigned int hdrlen = ip_hdrlen(skb);
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struct nf_conntrack_tuple target;
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unsigned long statusbit;
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WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);
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if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
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return 0;
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if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
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return 0;
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inside = (void *)skb->data + hdrlen;
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if (inside->icmp.type == ICMP_REDIRECT) {
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if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
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return 0;
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if (ct->status & IPS_NAT_MASK)
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return 0;
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}
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if (manip == NF_NAT_MANIP_SRC)
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statusbit = IPS_SRC_NAT;
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else
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statusbit = IPS_DST_NAT;
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/* Invert if this is reply direction */
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if (dir == IP_CT_DIR_REPLY)
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statusbit ^= IPS_NAT_MASK;
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if (!(ct->status & statusbit))
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return 1;
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if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
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&ct->tuplehash[!dir].tuple, !manip))
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return 0;
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if (skb->ip_summed != CHECKSUM_PARTIAL) {
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/* Reloading "inside" here since manip_pkt may reallocate */
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inside = (void *)skb->data + hdrlen;
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inside->icmp.checksum = 0;
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inside->icmp.checksum =
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csum_fold(skb_checksum(skb, hdrlen,
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skb->len - hdrlen, 0));
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}
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/* Change outer to look like the reply to an incoming packet */
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nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
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if (!nf_nat_ipv4_manip_pkt(skb, 0, &target, manip))
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return 0;
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return 1;
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}
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EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
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static unsigned int
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nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
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const struct nf_hook_state *state)
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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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ct = nf_ct_get(skb, &ctinfo);
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if (!ct)
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return NF_ACCEPT;
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if (ctinfo == IP_CT_RELATED || ctinfo == 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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state->hook))
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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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}
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return nf_nat_inet_fn(priv, skb, state);
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}
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static unsigned int
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nf_nat_ipv4_in(void *priv, struct sk_buff *skb,
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const struct nf_hook_state *state)
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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(priv, skb, state);
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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(void *priv, struct sk_buff *skb,
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const struct nf_hook_state *state)
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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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ret = nf_nat_ipv4_fn(priv, skb, state);
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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(state->net, 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(void *priv, struct sk_buff *skb,
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const struct nf_hook_state *state)
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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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ret = nf_nat_ipv4_fn(priv, skb, state);
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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(state->net, 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(state->net, 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 const struct nf_hook_ops nf_nat_ipv4_ops[] = {
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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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.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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.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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.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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.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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int nf_nat_l3proto_ipv4_register_fn(struct net *net, const struct nf_hook_ops *ops)
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{
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return nf_nat_register_fn(net, ops, nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
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}
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EXPORT_SYMBOL_GPL(nf_nat_l3proto_ipv4_register_fn);
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void nf_nat_l3proto_ipv4_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
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{
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nf_nat_unregister_fn(net, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
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}
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EXPORT_SYMBOL_GPL(nf_nat_l3proto_ipv4_unregister_fn);
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static int __init nf_nat_l3proto_ipv4_init(void)
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{
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return nf_nat_l3proto_register(&nf_nat_l3proto_ipv4);
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}
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static void __exit nf_nat_l3proto_ipv4_exit(void)
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{
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nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4);
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}
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("nf-nat-" __stringify(AF_INET));
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module_init(nf_nat_l3proto_ipv4_init);
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module_exit(nf_nat_l3proto_ipv4_exit);
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