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188bab3ae0
When you've enabled conntrack and NAT as a module (standard case in all distributions), and you've also enabled the new conntrack netlink interface, loading ip_conntrack_netlink.ko will auto-load iptable_nat.ko. This causes a huge performance penalty, since for every packet you iterate the nat code, even if you don't want it. This patch splits iptable_nat.ko into the NAT core (ip_nat.ko) and the iptables frontend (iptable_nat.ko). Threfore, ip_conntrack_netlink.ko will only pull ip_nat.ko, but not the frontend. ip_nat.ko will "only" allocate some resources, but not affect runtime performance. This separation is also a nice step in anticipation of new packet filters (nf-hipac, ipset, pkttables) being able to use the NAT core. Signed-off-by: Harald Welte <laforge@netfilter.org> Signed-off-by: David S. Miller <davem@davemloft.net>
431 lines
12 KiB
C
431 lines
12 KiB
C
/* ip_nat_helper.c - generic support functions for NAT helpers
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*
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* (C) 2000-2002 Harald Welte <laforge@netfilter.org>
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* (C) 2003-2004 Netfilter Core Team <coreteam@netfilter.org>
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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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* 14 Jan 2002 Harald Welte <laforge@gnumonks.org>:
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* - add support for SACK adjustment
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* 14 Mar 2002 Harald Welte <laforge@gnumonks.org>:
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* - merge SACK support into newnat API
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* 16 Aug 2002 Brian J. Murrell <netfilter@interlinx.bc.ca>:
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* - make ip_nat_resize_packet more generic (TCP and UDP)
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* - add ip_nat_mangle_udp_packet
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*/
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#include <linux/config.h>
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#include <linux/module.h>
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#include <linux/kmod.h>
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#include <linux/types.h>
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#include <linux/timer.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter_ipv4.h>
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#include <net/checksum.h>
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#include <net/icmp.h>
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <net/udp.h>
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#define ASSERT_READ_LOCK(x)
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#define ASSERT_WRITE_LOCK(x)
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#include <linux/netfilter_ipv4/ip_conntrack.h>
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#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
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#include <linux/netfilter_ipv4/ip_nat.h>
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#include <linux/netfilter_ipv4/ip_nat_protocol.h>
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#include <linux/netfilter_ipv4/ip_nat_core.h>
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#include <linux/netfilter_ipv4/ip_nat_helper.h>
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#include <linux/netfilter_ipv4/listhelp.h>
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#if 0
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#define DEBUGP printk
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#define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos);
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#else
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#define DEBUGP(format, args...)
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#define DUMP_OFFSET(x)
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#endif
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static DEFINE_SPINLOCK(ip_nat_seqofs_lock);
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/* Setup TCP sequence correction given this change at this sequence */
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static inline void
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adjust_tcp_sequence(u32 seq,
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int sizediff,
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struct ip_conntrack *ct,
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enum ip_conntrack_info ctinfo)
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{
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int dir;
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struct ip_nat_seq *this_way, *other_way;
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DEBUGP("ip_nat_resize_packet: old_size = %u, new_size = %u\n",
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(*skb)->len, new_size);
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dir = CTINFO2DIR(ctinfo);
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this_way = &ct->nat.info.seq[dir];
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other_way = &ct->nat.info.seq[!dir];
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DEBUGP("ip_nat_resize_packet: Seq_offset before: ");
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DUMP_OFFSET(this_way);
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spin_lock_bh(&ip_nat_seqofs_lock);
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/* SYN adjust. If it's uninitialized, or this is after last
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* correction, record it: we don't handle more than one
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* adjustment in the window, but do deal with common case of a
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* retransmit */
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if (this_way->offset_before == this_way->offset_after
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|| before(this_way->correction_pos, seq)) {
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this_way->correction_pos = seq;
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this_way->offset_before = this_way->offset_after;
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this_way->offset_after += sizediff;
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}
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spin_unlock_bh(&ip_nat_seqofs_lock);
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DEBUGP("ip_nat_resize_packet: Seq_offset after: ");
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DUMP_OFFSET(this_way);
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}
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/* Frobs data inside this packet, which is linear. */
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static void mangle_contents(struct sk_buff *skb,
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unsigned int dataoff,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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unsigned char *data;
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BUG_ON(skb_is_nonlinear(skb));
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data = (unsigned char *)skb->nh.iph + dataoff;
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/* move post-replacement */
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memmove(data + match_offset + rep_len,
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data + match_offset + match_len,
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skb->tail - (data + match_offset + match_len));
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/* insert data from buffer */
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memcpy(data + match_offset, rep_buffer, rep_len);
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/* update skb info */
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if (rep_len > match_len) {
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DEBUGP("ip_nat_mangle_packet: Extending packet by "
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"%u from %u bytes\n", rep_len - match_len,
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skb->len);
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skb_put(skb, rep_len - match_len);
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} else {
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DEBUGP("ip_nat_mangle_packet: Shrinking packet from "
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"%u from %u bytes\n", match_len - rep_len,
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skb->len);
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__skb_trim(skb, skb->len + rep_len - match_len);
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}
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/* fix IP hdr checksum information */
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skb->nh.iph->tot_len = htons(skb->len);
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ip_send_check(skb->nh.iph);
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}
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/* Unusual, but possible case. */
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static int enlarge_skb(struct sk_buff **pskb, unsigned int extra)
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{
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struct sk_buff *nskb;
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if ((*pskb)->len + extra > 65535)
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return 0;
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nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC);
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if (!nskb)
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return 0;
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/* Transfer socket to new skb. */
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if ((*pskb)->sk)
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skb_set_owner_w(nskb, (*pskb)->sk);
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kfree_skb(*pskb);
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*pskb = nskb;
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return 1;
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}
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/* Generic function for mangling variable-length address changes inside
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* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
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* command in FTP).
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*
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* Takes care about all the nasty sequence number changes, checksumming,
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* skb enlargement, ...
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*
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* */
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int
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ip_nat_mangle_tcp_packet(struct sk_buff **pskb,
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struct ip_conntrack *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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struct iphdr *iph;
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struct tcphdr *tcph;
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int datalen;
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if (!skb_make_writable(pskb, (*pskb)->len))
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return 0;
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if (rep_len > match_len
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&& rep_len - match_len > skb_tailroom(*pskb)
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&& !enlarge_skb(pskb, rep_len - match_len))
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return 0;
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SKB_LINEAR_ASSERT(*pskb);
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iph = (*pskb)->nh.iph;
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tcph = (void *)iph + iph->ihl*4;
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mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4,
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match_offset, match_len, rep_buffer, rep_len);
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datalen = (*pskb)->len - iph->ihl*4;
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tcph->check = 0;
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tcph->check = tcp_v4_check(tcph, datalen, iph->saddr, iph->daddr,
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csum_partial((char *)tcph, datalen, 0));
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if (rep_len != match_len) {
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set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
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adjust_tcp_sequence(ntohl(tcph->seq),
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(int)rep_len - (int)match_len,
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ct, ctinfo);
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/* Tell TCP window tracking about seq change */
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ip_conntrack_tcp_update(*pskb, ct, CTINFO2DIR(ctinfo));
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}
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return 1;
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}
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EXPORT_SYMBOL(ip_nat_mangle_tcp_packet);
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/* Generic function for mangling variable-length address changes inside
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* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX
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* command in the Amanda protocol)
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*
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* Takes care about all the nasty sequence number changes, checksumming,
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* skb enlargement, ...
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*
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* XXX - This function could be merged with ip_nat_mangle_tcp_packet which
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* should be fairly easy to do.
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*/
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int
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ip_nat_mangle_udp_packet(struct sk_buff **pskb,
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struct ip_conntrack *ct,
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enum ip_conntrack_info ctinfo,
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unsigned int match_offset,
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unsigned int match_len,
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const char *rep_buffer,
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unsigned int rep_len)
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{
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struct iphdr *iph;
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struct udphdr *udph;
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/* UDP helpers might accidentally mangle the wrong packet */
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iph = (*pskb)->nh.iph;
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if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) +
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match_offset + match_len)
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return 0;
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if (!skb_make_writable(pskb, (*pskb)->len))
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return 0;
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if (rep_len > match_len
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&& rep_len - match_len > skb_tailroom(*pskb)
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&& !enlarge_skb(pskb, rep_len - match_len))
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return 0;
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iph = (*pskb)->nh.iph;
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udph = (void *)iph + iph->ihl*4;
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mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph),
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match_offset, match_len, rep_buffer, rep_len);
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/* update the length of the UDP packet */
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udph->len = htons((*pskb)->len - iph->ihl*4);
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/* fix udp checksum if udp checksum was previously calculated */
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if (udph->check) {
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int datalen = (*pskb)->len - iph->ihl * 4;
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udph->check = 0;
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udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
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datalen, IPPROTO_UDP,
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csum_partial((char *)udph,
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datalen, 0));
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}
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return 1;
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}
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EXPORT_SYMBOL(ip_nat_mangle_udp_packet);
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/* Adjust one found SACK option including checksum correction */
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static void
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sack_adjust(struct sk_buff *skb,
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struct tcphdr *tcph,
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unsigned int sackoff,
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unsigned int sackend,
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struct ip_nat_seq *natseq)
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{
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while (sackoff < sackend) {
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struct tcp_sack_block *sack;
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u_int32_t new_start_seq, new_end_seq;
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sack = (void *)skb->data + sackoff;
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if (after(ntohl(sack->start_seq) - natseq->offset_before,
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natseq->correction_pos))
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new_start_seq = ntohl(sack->start_seq)
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- natseq->offset_after;
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else
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new_start_seq = ntohl(sack->start_seq)
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- natseq->offset_before;
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new_start_seq = htonl(new_start_seq);
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if (after(ntohl(sack->end_seq) - natseq->offset_before,
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natseq->correction_pos))
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new_end_seq = ntohl(sack->end_seq)
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- natseq->offset_after;
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else
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new_end_seq = ntohl(sack->end_seq)
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- natseq->offset_before;
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new_end_seq = htonl(new_end_seq);
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DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n",
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ntohl(sack->start_seq), new_start_seq,
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ntohl(sack->end_seq), new_end_seq);
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tcph->check =
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ip_nat_cheat_check(~sack->start_seq, new_start_seq,
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ip_nat_cheat_check(~sack->end_seq,
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new_end_seq,
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tcph->check));
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sack->start_seq = new_start_seq;
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sack->end_seq = new_end_seq;
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sackoff += sizeof(*sack);
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}
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}
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/* TCP SACK sequence number adjustment */
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static inline unsigned int
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ip_nat_sack_adjust(struct sk_buff **pskb,
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struct tcphdr *tcph,
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struct ip_conntrack *ct,
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enum ip_conntrack_info ctinfo)
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{
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unsigned int dir, optoff, optend;
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optoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct tcphdr);
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optend = (*pskb)->nh.iph->ihl*4 + tcph->doff*4;
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if (!skb_make_writable(pskb, optend))
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return 0;
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dir = CTINFO2DIR(ctinfo);
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while (optoff < optend) {
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/* Usually: option, length. */
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unsigned char *op = (*pskb)->data + optoff;
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switch (op[0]) {
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case TCPOPT_EOL:
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return 1;
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case TCPOPT_NOP:
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optoff++;
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continue;
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default:
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/* no partial options */
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if (optoff + 1 == optend
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|| optoff + op[1] > optend
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|| op[1] < 2)
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return 0;
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if (op[0] == TCPOPT_SACK
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&& op[1] >= 2+TCPOLEN_SACK_PERBLOCK
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&& ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
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sack_adjust(*pskb, tcph, optoff+2,
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optoff+op[1],
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&ct->nat.info.seq[!dir]);
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optoff += op[1];
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}
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}
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return 1;
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}
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/* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
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int
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ip_nat_seq_adjust(struct sk_buff **pskb,
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struct ip_conntrack *ct,
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enum ip_conntrack_info ctinfo)
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{
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struct tcphdr *tcph;
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int dir, newseq, newack;
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struct ip_nat_seq *this_way, *other_way;
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dir = CTINFO2DIR(ctinfo);
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this_way = &ct->nat.info.seq[dir];
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other_way = &ct->nat.info.seq[!dir];
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if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
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return 0;
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tcph = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
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if (after(ntohl(tcph->seq), this_way->correction_pos))
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newseq = ntohl(tcph->seq) + this_way->offset_after;
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else
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newseq = ntohl(tcph->seq) + this_way->offset_before;
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newseq = htonl(newseq);
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if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
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other_way->correction_pos))
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newack = ntohl(tcph->ack_seq) - other_way->offset_after;
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else
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newack = ntohl(tcph->ack_seq) - other_way->offset_before;
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newack = htonl(newack);
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tcph->check = ip_nat_cheat_check(~tcph->seq, newseq,
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ip_nat_cheat_check(~tcph->ack_seq,
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newack,
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tcph->check));
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DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n",
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ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
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ntohl(newack));
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tcph->seq = newseq;
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tcph->ack_seq = newack;
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if (!ip_nat_sack_adjust(pskb, tcph, ct, ctinfo))
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return 0;
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ip_conntrack_tcp_update(*pskb, ct, dir);
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return 1;
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}
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EXPORT_SYMBOL(ip_nat_seq_adjust);
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/* Setup NAT on this expected conntrack so it follows master. */
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/* If we fail to get a free NAT slot, we'll get dropped on confirm */
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void ip_nat_follow_master(struct ip_conntrack *ct,
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struct ip_conntrack_expect *exp)
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{
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struct ip_nat_range range;
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/* This must be a fresh one. */
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BUG_ON(ct->status & IPS_NAT_DONE_MASK);
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/* Change src to where master sends to */
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range.flags = IP_NAT_RANGE_MAP_IPS;
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range.min_ip = range.max_ip
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= ct->master->tuplehash[!exp->dir].tuple.dst.ip;
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/* hook doesn't matter, but it has to do source manip */
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ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING);
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/* For DST manip, map port here to where it's expected. */
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range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED);
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range.min = range.max = exp->saved_proto;
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range.min_ip = range.max_ip
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= ct->master->tuplehash[!exp->dir].tuple.src.ip;
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/* hook doesn't matter, but it has to do destination manip */
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ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING);
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}
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EXPORT_SYMBOL(ip_nat_follow_master);
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