Processing of TCP packets

src/Makefile.am

@@ -8,6 +8,7 @@ wrapsix_wrapper_SOURCES = \
 			  ipv6.c ipv6.h \
 			  nat.c nat.h \
 			  radixtree.c radixtree.h \
+			  tcp.c tcp.h \
 			  transmitter.c transmitter.h \
 			  udp.c udp.h \
 			  wrapper.c wrapper.h

src/ipv4.c

@@ -22,6 +22,7 @@
 
 #include "icmp.h"
 #include "ipv4.h"
+#include "tcp.h"
 #include "udp.h"
 #include "wrapper.h"
 
@@ -51,7 +52,7 @@ int ipv4(struct s_ethernet *eth, char *packet)
 	switch (ip->proto) {
 		case IPPROTO_TCP:
 			printf("[Debug] IPv4 Protocol: TCP\n");
-			/*ipv4_tcp(eth, ip, payload, data_size);*/
+			tcp_ipv4(eth, ip, payload, data_size);
 			break;
 		case IPPROTO_UDP:
 			printf("[Debug] IPv4 Protocol: UDP\n");

src/ipv6.c

@@ -22,6 +22,7 @@
 
 #include "icmp.h"
 #include "ipv6.h"
+#include "tcp.h"
 #include "udp.h"
 #include "wrapper.h"
 
@@ -44,7 +45,7 @@ int ipv6(struct s_ethernet *eth, char *packet)
 	switch (ip->next_header) {
 		case IPPROTO_TCP:
 			printf("[Debug] IPv6 Protocol: TCP\n");
-			/*ipv6_tcp(eth, ip, payload);*/
+			tcp_ipv6(eth, ip, payload);
 			break;
 		case IPPROTO_UDP:
 			printf("[Debug] IPv6 Protocol: UDP\n");

src/tcp.c

@@ -0,0 +1,220 @@
+/*
+ *  WrapSix
+ *  Copyright (C) 2008-2012  Michal Zima <xhire@mujmalysvet.cz>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as
+ *  published by the Free Software Foundation, either version 3 of the
+ *  License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <net/ethernet.h>	/* ETHERTYPE_* */
+#include <netinet/in.h>		/* htons */
+#include <stdio.h>
+#include <stdlib.h>		/* malloc */
+#include <string.h>		/* memcpy */
+
+#include "checksum.h"
+#include "ethernet.h"
+#include "ipv4.h"
+#include "ipv6.h"
+#include "nat.h"
+#include "tcp.h"
+#include "transmitter.h"
+#include "wrapper.h"
+
+/**
+ * Processing of incoming TCPv4 packets. Directly sends translated TCPv6
+ * packets.
+ *
+ * @param	eth4		Ethernet header
+ * @param	ip4		IPv4 header
+ * @param	payload		TCPv4 data
+ * @param	payload_size	Size of payload; needed because IPv4 header has
+ * 				dynamic length
+ *
+ * @return	0 for success
+ * @return	1 for failure
+ */
+int tcp_ipv4(struct s_ethernet *eth, struct s_ipv4 *ip4, char *payload,
+	     unsigned short payload_size)
+{
+	struct s_tcp  *tcp;
+	struct s_nat  *connection;
+	unsigned short orig_checksum;
+	unsigned char *packet;
+
+	struct s_ethernet *eth6;
+	struct s_ipv6 *ip6;
+
+	/* parse TCP header */
+	tcp = (struct s_tcp *) payload;
+
+	/* checksum recheck */
+	if (tcp->checksum != 0x0000) {
+		orig_checksum = tcp->checksum;
+		tcp->checksum = 0;
+		tcp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
+					      payload_size, IPPROTO_TCP,
+					      (unsigned char *) tcp);
+
+		if (tcp->checksum != orig_checksum) {
+			/* packet is corrupted and shouldn't be processed */
+			printf("[Debug] Wrong checksum\n");
+			return 1;
+		}
+	}
+
+	/* find connection in NAT */
+	connection = nat_in(nat4_tcp, ip4->ip_src, tcp->port_src, tcp->port_dest);
+
+	if (connection == NULL) {
+		printf("[Debug] Incoming connection wasn't found in NAT\n");
+		return 1;
+	}
+
+	/* allocate memory for translated packet */
+	if ((packet = (unsigned char *) malloc(sizeof(struct s_ethernet) +
+					       sizeof(struct s_ipv6) +
+					       payload_size)) == NULL) {
+		fprintf(stderr, "[Error] Lack of free memory\n");
+		return 1;
+	}
+	eth6 = (struct s_ethernet *) packet;
+	ip6 = (struct s_ipv6 *) (packet + sizeof(struct s_ethernet));
+
+	/* build ethernet header */
+	eth6->dest		= connection->mac;
+	eth6->src		= mac;
+	eth6->type		= htons(ETHERTYPE_IPV6);
+
+	/* build IPv6 packet */
+	ip6->ver		= 0x60;
+	ip6->traffic_class	= 0x0;
+	ip6->flow_label		= 0x0;
+	ip6->len		= htons(payload_size);
+	ip6->next_header	= IPPROTO_TCP;
+	ip6->hop_limit		= ip4->ttl;
+	ipv4_to_ipv6(&ip4->ip_src, &ip6->ip_src);
+	memcpy(&ip6->ip_dest, &connection->ipv6, sizeof(struct s_ipv6_addr));
+
+	/* set incoming source port */
+	tcp->port_dest = connection->ipv6_port_src;
+
+	/* compute TCP checksum */
+	tcp->checksum = 0x0;
+	tcp->checksum = checksum_ipv6(ip6->ip_src, ip6->ip_dest, payload_size,
+				      IPPROTO_TCP, (unsigned char *) tcp);
+
+	/* copy the payload data (with new checksum) */
+	memcpy(packet + sizeof(struct s_ethernet) + sizeof(struct s_ipv6),
+	       payload, payload_size);
+
+	/* send translated packet */
+	transmit_raw(packet, sizeof(struct s_ethernet) + sizeof(struct s_ipv6) +
+		     payload_size);
+
+	/* clean-up */
+	free(packet);
+
+	return 0;
+}
+
+/**
+ * Processing of outgoing TCPv6 packets. Directly sends translated TCPv4
+ * packets.
+ *
+ * @param	eth6		Ethernet header
+ * @param	ip6		IPv6 header
+ * @param	payload		TCPv6 data
+ *
+ * @return	0 for success
+ * @return	1 for failure
+ */
+int tcp_ipv6(struct s_ethernet *eth, struct s_ipv6 *ip6, char *payload)
+{
+	struct s_tcp  *tcp;
+	struct s_nat  *connection;
+	unsigned short orig_checksum;
+	struct s_ipv4 *ip4;
+	unsigned char *packet;
+	unsigned int   packet_size;
+
+	/* parse TCP header */
+	tcp = (struct s_tcp *) payload;
+
+	/* checksum recheck */
+	orig_checksum = tcp->checksum;
+	tcp->checksum = 0;
+	tcp->checksum = checksum_ipv6(ip6->ip_src, ip6->ip_dest,
+				      htons(ip6->len), IPPROTO_TCP,
+				      (unsigned char *) payload);
+
+	if (tcp->checksum != orig_checksum) {
+		/* packet is corrupted and shouldn't be processed */
+		printf("[Debug] Wrong checksum\n");
+		return 1;
+	}
+
+	/* find connection in NAT */
+	connection = nat_out(nat6_tcp, nat4_tcp, eth->src,
+			     ip6->ip_src, ip6->ip_dest,
+			     tcp->port_src, tcp->port_dest);
+
+	if (connection == NULL) {
+		printf("[Debug] Error! Outgoing connection wasn't "
+		       "found/created in NAT!\n");
+		return 1;
+	}
+
+	/* allocate memory for translated packet */
+	packet_size = sizeof(struct s_ipv4) + ip6->len;
+	if ((packet = (unsigned char *) malloc(packet_size)) == NULL) {
+		fprintf(stderr, "[Error] Lack of free memory\n");
+		return 1;
+	}
+	ip4 = (struct s_ipv4 *) packet;
+
+	/* build IPv4 packet */
+	ip4->ver_hdrlen	  = 0x45;		/* ver 4, header length 20 B */
+	ip4->tos	  = 0x0;
+	ip4->len	  = htons(sizeof(struct s_ipv4) + htons(ip6->len));
+	ip4->id		  = 0x0;
+	ip4->flags_offset = htons(IPV4_FLAG_DONT_FRAGMENT);
+	ip4->ttl	  = ip6->hop_limit;
+	ip4->proto	  = IPPROTO_TCP;
+	ipv6_to_ipv4(&ip6->ip_dest, &ip4->ip_dest);
+	memcpy(&ip4->ip_src, &wrapsix_ipv4_addr, sizeof(struct s_ipv4_addr));
+
+	/* set outgoing source port */
+	tcp->port_src = connection->ipv4_port_src;
+
+	/* compute TCP checksum */
+	tcp->checksum = 0;
+	tcp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
+				      htons(ip6->len), IPPROTO_TCP,
+				      (unsigned char *) tcp);
+
+	/* copy the payload data (with new checksum) */
+	memcpy(packet + sizeof(struct s_ipv4), payload, htons(ip6->len));
+
+	/* compute IPv4 checksum */
+	ip4->checksum = 0x0;
+	ip4->checksum = checksum(ip4, sizeof(struct s_ipv4));
+
+	/* send translated packet */
+	transmit_ipv4(&ip4->ip_dest, packet, htons(ip4->len));
+
+	/* clean-up */
+	free(packet);
+
+	return 0;
+}

src/tcp.h

@@ -0,0 +1,40 @@
+/*
+ *  WrapSix
+ *  Copyright (C) 2008-2012  Michal Zima <xhire@mujmalysvet.cz>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as
+ *  published by the Free Software Foundation, either version 3 of the
+ *  License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef TCP_H
+#define TCP_H
+
+/* TCP header structure */
+struct s_tcp {
+	unsigned short port_src;	/* 16 b; source port */
+	unsigned short port_dest;	/* 16 b; destination port */
+	unsigned int   seq;		/* 32 b; sequence number */
+	unsigned int   ack;		/* 32 b; acknowledgement number */
+	unsigned char  offset;		/*  4 b; data offset
+					    6 b; reserved (zeros) */
+	unsigned char  flags;		/*  6 b; flags */
+	unsigned short window;		/* 16 b; size of the receive window */
+	unsigned short checksum;	/* 16 b */
+	unsigned short urgent_ptr;	/* 16 b; ptr to last urgent data byte */
+} __attribute__ ((__packed__));
+
+int tcp_ipv4(struct s_ethernet *eth, struct s_ipv4 *ip4, char *payload,
+	     unsigned short payload_size);
+int tcp_ipv6(struct s_ethernet *eth, struct s_ipv6 *ip6, char *payload);
+
+#endif /* TCP_H */

src/udp.c

@@ -211,7 +211,6 @@ int udp_ipv6(struct s_ethernet *eth, struct s_ipv6 *ip6, char *payload)
 	ip4->checksum = checksum(ip4, sizeof(struct s_ipv4));
 
 	/* send translated packet */
-	printf("[Debug] transmitting\n");
 	transmit_ipv4(&ip4->ip_dest, packet, htons(ip4->len));
 
 	/* clean-up */