patch-2.1.15 linux/net/ipv4/ip_nat_dumb.c

• Lines: 78
• Date: Thu Dec 12 16:54:24 1996
• Orig file: v2.1.14/linux/net/ipv4/ip_nat_dumb.c
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v2.1.14/linux/net/ipv4/ip_nat_dumb.c linux/net/ipv4/ip_nat_dumb.c
@@ -0,0 +1,77 @@
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Dumb Network Address Translation.
+ *
+ * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ *
+ * NOTE:	It is just working model of real NAT.
+ */
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/icmp.h>
+#include <linux/netdevice.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/firewall.h>
+#include <linux/ip_fw.h>
+#ifdef CONFIG_IP_MASQUERADE
+#include <net/ip_masq.h>
+#endif
+#include <net/checksum.h>
+#include <linux/route.h>
+#include <net/route.h>
+
+
+int
+ip_do_nat(struct sk_buff *skb)
+{
+	struct rtable *rt = (struct rtable*)skb->dst;
+	struct iphdr *iph = skb->nh.iph;
+	u32 odaddr = iph->daddr;
+	u32 osaddr = iph->saddr;
+	u16	check;
+	u16	*cksum = NULL;
+
+	IPCB(skb)->flags |= IPSKB_TRANSLATED;
+
+	/* Rewrite IP header */
+	iph->daddr = rt->rt_dst_map;
+	iph->saddr = rt->rt_src_map;
+	iph->check = 0;
+	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
+
+	/* If it is the first fragment, rewrite protocol headers */
+
+	if (!(iph->frag_off & htons(IP_OFFSET))) {
+		/* Only plain TCP/UDP headers rewriting is implemented :-( */
+		if (iph->protocol == IPPROTO_TCP)
+			cksum = (u16*)&((struct tcphdr*)(((char*)iph) + iph->ihl*4))->check;
+		else if (iph->protocol == IPPROTO_UDP)
+			cksum = (u16*)&((struct udphdr*)(((char*)iph) + iph->ihl*4))->check;
+		if (cksum && (check = *cksum) != 0) {
+			check = csum_tcpudp_magic(iph->saddr, iph->daddr, 0, 0, ~check);
+			check = csum_tcpudp_magic(~osaddr, ~odaddr, 0, 0, ~check);
+			if (!check)
+				check = 0xFFFF;
+			*cksum = check;
+		}
+	}
+	return 0;
+}