A bit of code cleanup

src/icmp.c

@@ -115,8 +115,8 @@ int icmp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4,
 	eth6->type		= htons(ETHERTYPE_IPV6);
 
 	/* build IPv6 packet */
-	ip6->ver		= 0x60;
+	ip6->ver		= 0x60 | (ip4->tos >> 4);
-	ip6->traffic_class	= 0x0;
+	ip6->traffic_class	= ip4->tos << 4;
 	ip6->flow_label		= 0x0;
 	ip6->len		= htons(payload_size);
 	ip6->next_header	= IPPROTO_ICMPV6;
@@ -228,7 +228,8 @@ int icmp_ipv6(struct s_ethernet *eth6, struct s_ipv6 *ip6, char *payload)
 
 	/* build IPv4 packet */
 	ip4->ver_hdrlen	  = 0x45;		/* ver 4, header length 20 B */
-	ip4->tos	  = 0x0;
+	ip4->tos	  = ((ip6->ver & 0x0f) << 4) |
+			    ((ip6->traffic_class & 0xf0) >> 4);
 	ip4->len	  = htons(sizeof(struct s_ipv4) + htons(ip6->len));
 	ip4->id		  = 0x0;
 	ip4->flags_offset = htons(IPV4_FLAG_DONT_FRAGMENT);
@@ -250,7 +251,6 @@ int icmp_ipv6(struct s_ethernet *eth6, struct s_ipv6 *ip6, char *payload)
 				      (unsigned char *) icmp);
 
 	/* send translated packet */
-	printf("[Debug] transmitting\n");
 	transmit_ipv4(&ip4->ip_dest, packet, htons(ip4->len));
 
 	/* clean-up */
@@ -320,8 +320,7 @@ int icmp_ndp(struct s_ethernet *ethq, struct s_ipv6 *ipq,
 
 	/* ICMP */
 	icmp->type = ICMPV6_NDP_NA;
-	icmp->code = 0;
+	/* code = checksum = 0 by memset */
-	icmp->checksum = 0;
 
 	/* NDP NA */
 	ndp_na->flags	 = INNAF_S;

src/ipv4.c

@@ -26,6 +26,15 @@
 #include "udp.h"
 #include "wrapper.h"
 
+/**
+ * Processing of IPv4 packets.
+ *
+ * @param	eth	Ethernet header
+ * @param	packet	Packet data
+ *
+ * @return	0 for success
+ * @return	1 for failure
+ */
 int ipv4(struct s_ethernet *eth, char *packet)
 {
 	struct s_ipv4	*ip;
@@ -42,8 +51,6 @@ int ipv4(struct s_ethernet *eth, char *packet)
 		return 1;
 	}
 
-	/* TODO: verify checksum */
-
 	/* compute sizes and get payload */
 	header_size = (ip->ver_hdrlen & 0x0f) * 4;	/* # of 4 byte words */
 	data_size = htons(ip->len) - header_size;
@@ -52,21 +59,16 @@ int ipv4(struct s_ethernet *eth, char *packet)
 	switch (ip->proto) {
 		case IPPROTO_TCP:
 			printf("[Debug] IPv4 Protocol: TCP\n");
-			tcp_ipv4(eth, ip, payload, data_size);
+			return tcp_ipv4(eth, ip, payload, data_size);
-			break;
 		case IPPROTO_UDP:
 			printf("[Debug] IPv4 Protocol: UDP\n");
-			udp_ipv4(eth, ip, payload, data_size);
+			return udp_ipv4(eth, ip, payload, data_size);
-			break;
 		case IPPROTO_ICMP:
 			printf("[Debug] IPv4 Protocol: ICMP\n");
-			icmp_ipv4(eth, ip, payload, data_size);
+			return icmp_ipv4(eth, ip, payload, data_size);
-			break;
 		default:
 			printf("[Debug] IPv4 Protocol: unknown [%d/0x%x]\n",
 			       ip->proto, ip->proto);
 			return 1;
 	}
-
-	return 0;
 }

src/ipv6.c

@@ -26,6 +26,15 @@
 #include "udp.h"
 #include "wrapper.h"
 
+/**
+ * Processing of IPv6 packets.
+ *
+ * @param	eth	Ethernet header
+ * @param	packet	Packet data
+ *
+ * @return	0 for success
+ * @return	1 for failure
+ */
 int ipv6(struct s_ethernet *eth, char *packet)
 {
 	struct s_ipv6	*ip;
@@ -45,21 +54,16 @@ int ipv6(struct s_ethernet *eth, char *packet)
 	switch (ip->next_header) {
 		case IPPROTO_TCP:
 			printf("[Debug] IPv6 Protocol: TCP\n");
-			tcp_ipv6(eth, ip, payload);
+			return tcp_ipv6(eth, ip, payload);
-			break;
 		case IPPROTO_UDP:
 			printf("[Debug] IPv6 Protocol: UDP\n");
-			udp_ipv6(eth, ip, payload);
+			return udp_ipv6(eth, ip, payload);
-			break;
 		case IPPROTO_ICMPV6:
 			printf("[Debug] IPv6 Protocol: ICMP\n");
-			icmp_ipv6(eth, ip, payload);
+			return icmp_ipv6(eth, ip, payload);
-			break;
 		default:
 			printf("[Debug] IPv6 Protocol: unknown [%d/0x%x]\n",
 			       ip->next_header, ip->next_header);
 			return 1;
 	}
-
-	return 0;
 }

src/nat.c

@@ -1,6 +1,6 @@
 /*
  *  WrapSix
- *  Copyright (C) 2008-2011  Michal Zima <xhire@mujmalysvet.cz>
+ *  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
@@ -50,6 +50,9 @@ radixtree_t *nat6_tcp, *nat6_udp, *nat6_icmp,
 	    *nat4_tcp, *nat4_udp, *nat4_icmp,
 	    *nat4_tcp_fragments;
 
+/**
+ * Initialization of NAT tables.
+ */
 void nat_init(void)
 {
 	nat6_tcp  = radixtree_create();
@@ -63,6 +66,9 @@ void nat_init(void)
 	nat4_tcp_fragments = radixtree_create();
 }
 
+/**
+ * Clean-up of NAT tables.
+ */
 void nat_quit(void)
 {
 	/* 128 + 16 + 32 + 16 = 192 / 6 = 32 */
@@ -79,6 +85,20 @@ void nat_quit(void)
 	radixtree_destroy(nat4_tcp_fragments, 8);
 }
 
+/**
+ * Lookup or create NAT connection for outgoing IPv6 packet.
+ *
+ * @param      nat_proto6      IPv6 NAT table
+ * @param      nat_proto4      IPv4 NAT table
+ * @param      eth_src         Source MAC address
+ * @param      ipv6_src        Source IPv6 address
+ * @param      ipv6_dst        Destination IPv6 address
+ * @param      port_src        Source port
+ * @param      port_dst        Destination port
+ *
+ * @return     NULL when it wasn't possible to create connection
+ * @return     pointer to connection structure otherwise
+ */
 struct s_nat *nat_out(radixtree_t *nat_proto6, radixtree_t *nat_proto4,
 		      struct s_mac_addr eth_src,
 		      struct s_ipv6_addr ipv6_src, struct s_ipv6_addr ipv6_dst,
@@ -137,6 +157,17 @@ struct s_nat *nat_out(radixtree_t *nat_proto6, radixtree_t *nat_proto4,
 	}
 }
 
+/**
+ * Lookup NAT connection for incoming IPv4 packet.
+ *
+ * @param      nat_proto4      NAT table
+ * @param      ipv4_src        Source IPv4 address
+ * @param      port_src        Source port
+ * @param      port_dst        Destination port
+ *
+ * @return     NULL when no connection was found
+ * @return     pointer to connection structure otherwise
+ */
 struct s_nat *nat_in(radixtree_t *nat_proto4, struct s_ipv4_addr ipv4_src,
 		     unsigned short port_src, unsigned short port_dst)
 {
@@ -225,7 +256,7 @@ struct s_nat *nat_in_fragments(radixtree_t *nat_proto4,
  * @param	ipv4_src	Source IPv4 address
  * @param	id		Fragment identification
  */
-void nat_in_fragments_clenup(radixtree_t *nat_proto4,
+void nat_in_fragments_cleanup(radixtree_t *nat_proto4,
 			      struct s_ipv4_addr ipv4_src, unsigned short id)
 {
 	/* create structure to search in the tree */

src/nat.h

@@ -1,6 +1,6 @@
 /*
  *  WrapSix
- *  Copyright (C) 2008-2011  Michal Zima <xhire@mujmalysvet.cz>
+ *  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
@@ -53,7 +53,7 @@ struct s_nat *nat_in(radixtree_t *nat_proto4, struct s_ipv4_addr ipv4_src,
 struct s_nat *nat_in_fragments(radixtree_t *nat_proto4,
 			       struct s_ipv4_addr ipv4_src,
 			       unsigned short id, struct s_nat *nat);
-void nat_in_fragments_clenup(radixtree_t *nat_proto4,
+void nat_in_fragments_cleanup(radixtree_t *nat_proto4,
 			      struct s_ipv4_addr ipv4_src, unsigned short id);
 
 #endif /* NAT_H */

src/radixtree.c

@@ -22,6 +22,11 @@
 
 #include "radixtree.h"
 
+/**
+ * Creates root of radix tree.
+ *
+ * @return     Root of new radix tree
+ */
 radixtree_t *radixtree_create(void)
 {
 	radixtree_t *radixtree;
@@ -36,21 +41,36 @@ radixtree_t *radixtree_create(void)
 	return radixtree;
 }
 
-void radixtree_destroy(radixtree_t *t, unsigned char depth)
+/**
+ * Destroys a radix tree.
+ *
+ * @param      root    Root of the tree to destroy
+ * @param      depth   Depth of the tree
+ */
+void radixtree_destroy(radixtree_t *root, unsigned char depth)
 {
 	unsigned char i;
 
 	for (i = 0; i < ARRAY_SIZE; i++) {
-		if (depth != 1 && t->array[i] != NULL) {
+		if (depth != 1 && root->array[i] != NULL) {
-			radixtree_destroy(t->array[i], depth - 1);
+			radixtree_destroy(root->array[i], depth - 1);
 		} else if (depth == 1) {
-			free(t->array[i]);
+			free(root->array[i]);
 		}
 	}
 
-	free(t);
+	free(root);
 }
 
+/**
+ * Inserts new data entry into the tree.
+ *
+ * @param      root            Root of the radix tree
+ * @param      chunker         Function to use to get chunks for indexing internal array
+ * @param      search_data     Key used to search in the tree
+ * @param      size            Length of the key
+ * @param      data            Data to store in the tree
+ */
 void radixtree_insert(radixtree_t *root,
 		      unsigned char *(chunker)(void *data, unsigned char size, unsigned char *count),
 		      void *search_data, unsigned char size, void *data)
@@ -85,6 +105,14 @@ void radixtree_insert(radixtree_t *root,
 	free(chunks);
 }
 
+/**
+ * Deletes an entry from the tree.
+ *
+ * @param      root            Root of the radix tree
+ * @param      chunker         Function to use to get chunks for indexing internal array
+ * @param      data            Key used to search in the tree
+ * @param      size            Length of the key
+ */
 void radixtree_delete(radixtree_t *root,
 		      unsigned char *(chunker)(void *data, unsigned char size, unsigned char *count),
 		      void *data, unsigned char size)
@@ -97,7 +125,7 @@ void radixtree_delete(radixtree_t *root,
 
 	chunks = chunker(data, size, &chunk_count);
 
-	for (i = 0, tmp = root; i < chunk_count && tmp != NULL; i++, tmp = tmp->array[chunks[i]]) {
+	for (i = 0, tmp = root; i < chunk_count && tmp != NULL; tmp = tmp->array[chunks[i++]]) {
 		flags = tmp->count == 1 ? flags | (0x1 << i) : 0;
 
 		if (i + 1 == chunk_count) {
@@ -128,6 +156,14 @@ void radixtree_delete(radixtree_t *root,
 	free(chunks);
 }
 
+/**
+ * Lookups an entry in the tree.
+ *
+ * @param      root            Root of the radix tree
+ * @param      chunker         Function to use to get chunks for indexing internal array
+ * @param      data            Key used to search in the tree
+ * @param      size            Length of the key
+ */
 void *radixtree_lookup(radixtree_t *root,
 		       unsigned char *(chunker)(void *data, unsigned char size, unsigned char *count),
 		       void *data, unsigned char size)

src/radixtree.h

@@ -1,6 +1,6 @@
 /*
  *  WrapSix
- *  Copyright (C) 2008-2011  Michal Zima <xhire@mujmalysvet.cz>
+ *  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
@@ -28,7 +28,7 @@ typedef struct radixtree {
 } radixtree_t;
 
 radixtree_t *radixtree_create(void);
-void radixtree_destroy(radixtree_t *t, unsigned char depth);
+void radixtree_destroy(radixtree_t *root, unsigned char depth);
 void radixtree_insert(radixtree_t *root,
 		      unsigned char *(chunker)(void *data, unsigned char size, unsigned char *count),
 		      void *search_data, unsigned char size, void *data);

src/tcp.c

@@ -57,12 +57,12 @@ int tcp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4, char *payload,
 	struct s_ipv6_fragment	*frag;
 
 	/* full processing of unfragmented packet or the first fragment with
-	 * TCP header with checksum field (this is safe)
+	 * TCP header
 	 */
 	if ((ip4->flags_offset & htons(IPV4_FLAG_DONT_FRAGMENT)) ||
 	    ((ip4->flags_offset & htons(IPV4_FLAG_MORE_FRAGMENTS)) &&
 	     (ip4->flags_offset & 0xff1f) == 0x0000 &&
-	     payload_size >= sizeof(struct s_tcp) - 2)) {
+	     payload_size >= sizeof(struct s_tcp))) {
 		/* parse TCP header */
 		tcp = (struct s_tcp *) payload;
 
@@ -249,8 +249,8 @@ int tcp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4, char *payload,
 					 sizeof(struct s_ipv6_fragment));
 
 			/* fill in missing IPv6 fragment header fields */
-			frag->offset_flag = htons((htons(ip4->flags_offset) << 3) |
+			frag->offset_flag = htons((htons(ip4->flags_offset) <<
-						  IPV6_FLAG_MORE_FRAGMENTS);
+						  3) | IPV6_FLAG_MORE_FRAGMENTS);
 
 			/* copy the payload data */
 			memcpy((unsigned char *) frag +
@@ -264,7 +264,8 @@ int tcp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4, char *payload,
 			ip6->len = htons(payload_size +
 					 sizeof(struct s_ipv6_fragment) -
 					 FRAGMENT_LEN);
-			frag->offset_flag = htons((htons(ip4->flags_offset) +
+			frag->offset_flag = htons(((htons(ip4->flags_offset) &
+						  0xfffc) +
 						  FRAGMENT_LEN / 8) << 3);
 			if (ip4->flags_offset &
 			    htons(IPV4_FLAG_MORE_FRAGMENTS)) {
@@ -378,7 +379,8 @@ int tcp_ipv6(struct s_ethernet *eth6, struct s_ipv6 *ip6, char *payload)
 
 	/* build IPv4 packet */
 	ip4->ver_hdrlen	  = 0x45;		/* ver 4, header length 20 B */
-	ip4->tos	  = 0x0;
+	ip4->tos	  = ((ip6->ver & 0x0f) << 4) |
+			    ((ip6->traffic_class & 0xf0) >> 4);
 	ip4->len	  = htons(sizeof(struct s_ipv4) + htons(ip6->len));
 	ip4->id		  = 0x0;
 	ip4->flags_offset = htons(IPV4_FLAG_DONT_FRAGMENT);

src/tcp.h

@@ -30,7 +30,6 @@ struct s_tcp {
 	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 *eth4, struct s_ipv4 *ip4, char *payload,

src/transmitter.c

@@ -18,7 +18,8 @@
 
 #include <net/if.h>		/* struct ifreq */
 #include <netinet/if_ether.h>	/* {P,A}F_PACKET, ETH_P_*, socket, SOCK_RAW,
-				 * setsockopt, SOL_SOCKET, SO_BINDTODEVICE, sendto */
+				 * setsockopt, SOL_SOCKET, SO_BINDTODEVICE,
+				 * sendto */
 #include <netinet/in.h>		/* htons */
 #include <netpacket/packet.h>	/* sockaddr_ll, PACKET_OTHERHOST */
 #include <stdio.h>		/* fprintf, stderr, perror */
@@ -34,7 +35,8 @@ struct sockaddr_in	socket_address_ipv4;
 int			sock, sock_ipv4;
 
 /**
- * Initialize socket and all needed properties. Should be called only once on program startup.
+ * Initialize sockets and all needed properties. Should be called only once on
+ * program startup.
  *
  * @return		0 for success
  * @return		1 for failure
@@ -45,10 +47,10 @@ int transmission_init(void)
 
 	/** RAW socket **/
 	/* prepare settings for RAW socket */
-	socket_address.sll_family	= PF_PACKET;			/* RAW communication */
+	socket_address.sll_family	= PF_PACKET;	/* raw communication */
-	socket_address.sll_protocol	= htons(ETH_P_IP);		/* protocol above the ethernet layer */
+	socket_address.sll_protocol	= htons(ETH_P_IP);	/* L3 proto */
-	socket_address.sll_ifindex	= interface.ifr_ifindex;	/* set index of the network device */
+	socket_address.sll_ifindex	= interface.ifr_ifindex;
-	socket_address.sll_pkttype	= PACKET_OTHERHOST;		/* target host is another host */
+	socket_address.sll_pkttype	= PACKET_OTHERHOST;
 
 	/* initialize RAW socket */
 	if ((sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL))) == -1) {
@@ -58,8 +60,10 @@ int transmission_init(void)
 	}
 
 	/* bind the socket to the interface */
-	if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, &interface, sizeof(struct ifreq)) == -1) {
+	if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, &interface,
-		fprintf(stderr, "[Error] Couldn't bind the socket to the interface.\n");
+	    sizeof(struct ifreq)) == -1) {
+		fprintf(stderr, "[Error] Couldn't bind the socket to the "
+				"interface.\n");
 		perror("setsockopt()");
 		return 1;
 	}
@@ -78,8 +82,10 @@ int transmission_init(void)
 	}
 
 	/* we will provide our own IPv4 header */
-	if (setsockopt(sock_ipv4, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)) == -1) {
+	if (setsockopt(sock_ipv4, IPPROTO_IP, IP_HDRINCL, &on,
-		fprintf(stderr, "[Error] Couldn't apply the socket settings.\n");
+	    sizeof(on)) == -1) {
+		fprintf(stderr, "[Error] Couldn't apply the socket "
+				"settings.\n");
 		perror("setsockopt()");
 		return 1;
 	}
@@ -88,7 +94,7 @@ int transmission_init(void)
 }
 
 /**
- * Close socket. Should be called only once on program shutdown.
+ * Close sockets. Should be called only once on program shutdown.
  *
  * @return		0 for success
  * @return		1 for failure
@@ -97,7 +103,8 @@ int transmission_quit(void)
 {
 	/* close the socket */
 	if (close(sock) || close(sock_ipv4)) {
-		fprintf(stderr, "[Error] Couldn't close the transmission sockets.\n");
+		fprintf(stderr, "[Error] Couldn't close the transmission "
+				"sockets.\n");
 		perror("close()");
 		return 1;
 	} else {
@@ -116,7 +123,8 @@ int transmission_quit(void)
  */
 int transmit_raw(unsigned char *data, unsigned int length)
 {
-	if (sendto(sock, data, length, 0, (struct sockaddr *) &socket_address, sizeof(struct sockaddr_ll)) != (int) length) {
+	if (sendto(sock, data, length, 0, (struct sockaddr *) &socket_address,
+	    sizeof(struct sockaddr_ll)) != (int) length) {
 		fprintf(stderr, "[Error] Couldn't send a RAW packet.\n");
 		perror("sendto()");
 		return 1;
@@ -129,18 +137,23 @@ int transmit_raw(unsigned char *data, unsigned int length)
  * Send IPv4 packet with IPv4 header supplied. Ethernet header is added by OS.
  *
  * @param	ip	Destination IPv4 address
- * @param	data	Raw packet data, excluding ethernet header, but including IPv4 header
+ * @param	data	Raw packet data, excluding ethernet header, but
+ * 			including IPv4 header
  * @param	length	Length of the whole packet in bytes
  *
  * @return		0 for success
  * @return		1 for failure
  */
-int transmit_ipv4(struct s_ipv4_addr *ip, unsigned char *data, unsigned int length)
+int transmit_ipv4(struct s_ipv4_addr *ip, unsigned char *data,
+		  unsigned int length)
 {
 	/* set the destination IPv4 address */
-	memcpy(&socket_address_ipv4.sin_addr.s_addr, ip, sizeof(struct s_ipv4_addr));
+	memcpy(&socket_address_ipv4.sin_addr.s_addr, ip,
+	       sizeof(struct s_ipv4_addr));
 
-	if (sendto(sock_ipv4, data, length, 0, (struct sockaddr *) &socket_address_ipv4, sizeof(struct sockaddr)) != (int) length) {
+	if (sendto(sock_ipv4, data, length, 0,
+	    (struct sockaddr *) &socket_address_ipv4,
+	    sizeof(struct sockaddr)) != (int) length) {
 		fprintf(stderr, "[Error] Couldn't send an IPv4 packet.\n");
 		perror("sendto()");
 		return 1;

src/udp.c

@@ -97,8 +97,8 @@ int udp_ipv4(struct s_ethernet *eth4, struct s_ipv4 *ip4, char *payload,
 	eth6->type		= htons(ETHERTYPE_IPV6);
 
 	/* build IPv6 packet */
-	ip6->ver		= 0x60;
+	ip6->ver		= 0x60 | (ip4->tos >> 4);
-	ip6->traffic_class	= 0x0;
+	ip6->traffic_class	= ip4->tos << 4;
 	ip6->flow_label		= 0x0;
 	ip6->len		= htons(payload_size);
 	ip6->next_header	= IPPROTO_UDP;
@@ -193,7 +193,8 @@ int udp_ipv6(struct s_ethernet *eth6, struct s_ipv6 *ip6, char *payload)
 
 	/* build IPv4 packet */
 	ip4->ver_hdrlen	  = 0x45;		/* ver 4, header length 20 B */
-	ip4->tos	  = 0x0;
+	ip4->tos	  = ((ip6->ver & 0x0f) << 4) |
+			    ((ip6->traffic_class & 0xf0) >> 4);
 	ip4->len	  = htons(sizeof(struct s_ipv4) + htons(ip6->len));
 	ip4->id		  = 0x0;
 	ip4->flags_offset = htons(IPV4_FLAG_DONT_FRAGMENT);

src/wrapper.c

@@ -37,10 +37,12 @@
 #include "transmitter.h"
 #include "wrapper.h"
 
-#define INTERFACE	"eth0"
+-/* +++ CONFIGURATION +++ */
-#define BUFFER_SIZE	65536
+#define INTERFACE	"eth0"	/* be sure to turn off generic-segmentation-offload! */
-#define PREFIX		"fd77::"
+#define PREFIX		"64:ff9b::"
 #define IPV4_ADDR	"192.168.0.111"
+/* --- CONFIGURATION --- */
+
 
 struct ifreq		interface;
 struct s_mac_addr	mac;

src/wrapper.h

@@ -22,7 +22,9 @@
 #include "ipv4.h"
 #include "ipv6.h"
 
+/* +++ CONFIGURE +++ */
 #define MTU 1280
+/* --- CONFIGURE --- */
 
 extern struct ifreq		interface;
 extern struct s_mac_addr	mac;