[B.A.T.M.A.N.] [PATCH] 32bit sequence number and TTL for broadcasts

[Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>]

This patch changes the sequence number range from 8 or 16 bit to 32 bit. 
This should avoid problems with the sequence number sliding window algorithm 
which we had seen in the past for broadcast floods or malicious packet 
injections. We can not assure 100% security with this patch, but it is quite
an improvement over the old 16 bit sequence numbers: 

 * expected window size can be increased (4096 -> 65536)
 * 64k packets in the right order would now be needed to cause a loop,
   which seems practically impossible.

Furthermore, a TTL field has been added to the broadcast packet type, just to
make sure.

These changes required to increase the compatibility level once again. It 
should therefore only applied to the upcoming 0.3 branch.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
---
Index: a/batman-adv-kernelland/vis.c
===================================================================
--- a/batman-adv-kernelland/vis.c	(revision 1639)
+++ a/batman-adv-kernelland/vis.c	(working copy)
@@ -309,7 +309,8 @@
 	old_info = hash_find(vis_hash, &search_elem);
 
 	if (old_info != NULL) {
-		if (!seq_after(vis_packet->seqno, old_info->packet.seqno)) {
+		if (!seq_after(ntohl(vis_packet->seqno),
+				ntohl(old_info->packet.seqno))) {
 			if (old_info->packet.seqno == vis_packet->seqno) {
 				recv_list_add(&old_info->recv_list,
 					      vis_packet->sender_orig);
@@ -477,7 +478,7 @@
 	spin_lock_irqsave(&orig_hash_lock, flags);
 	memcpy(info->packet.target_orig, broadcastAddr, ETH_ALEN);
 	info->packet.ttl = TTL;
-	info->packet.seqno++;
+	info->packet.seqno = htonl(ntohl(info->packet.seqno) + 1);
 	info->packet.entries = 0;
 
 	if (info->packet.vis_type == VIS_TYPE_CLIENT_UPDATE) {
Index: a/batman-adv-kernelland/types.h
===================================================================
--- a/batman-adv-kernelland/types.h	(revision 1639)
+++ a/batman-adv-kernelland/types.h	(working copy)
@@ -39,7 +39,7 @@
 	char if_status;
 	char addr_str[ETH_STR_LEN];
 	struct net_device *net_dev;
-	atomic_t seqno;
+	atomic64_t seqno;
 	unsigned char *packet_buff;
 	int packet_len;
 	struct kobject *hardif_obj;
@@ -63,10 +63,10 @@
 	uint8_t flags;    /* for now only VIS_SERVER flag. */
 	unsigned char *hna_buff;
 	int16_t hna_buff_len;
-	uint16_t last_real_seqno;   /* last and best known squence number */
+	uint32_t last_real_seqno;   /* last and best known sequence number */
 	uint8_t last_ttl;         /* ttl of last received packet */
 	TYPE_OF_WORD bcast_bits[NUM_WORDS];
-	uint16_t last_bcast_seqno;  /* last broadcast sequence number received by this host */
+	uint32_t last_bcast_seqno;  /* last received broadcast seqno */
 	struct list_head neigh_list;
 	struct {
 		uint8_t candidates;	/* how many candidates are available */
Index: a/batman-adv-kernelland/packet.h
===================================================================
--- a/batman-adv-kernelland/packet.h	(revision 1639)
+++ a/batman-adv-kernelland/packet.h	(working copy)
@@ -28,7 +28,7 @@
 #define BAT_VIS       0x05
 
 /* this file is included by batctl which needs these defines */
-#define COMPAT_VERSION 9
+#define COMPAT_VERSION 10
 #define DIRECTLINK 0x40
 #define VIS_SERVER 0x20
 #define PRIMARIES_FIRST_HOP 0x10
@@ -49,7 +49,7 @@
 	uint8_t  version;  /* batman version field */
 	uint8_t  flags;    /* 0x40: DIRECTLINK flag, 0x20 VIS_SERVER flag... */
 	uint8_t  tq;
-	uint16_t seqno;
+	uint32_t seqno;
 	uint8_t  orig[6];
 	uint8_t  prev_sender[6];
 	uint8_t  ttl;
@@ -99,15 +99,16 @@
 	uint8_t  packet_type;
 	uint8_t  version;  /* batman version field */
 	uint8_t  orig[6];
-	uint16_t seqno;
+	uint8_t  ttl;
+	uint32_t seqno;
 } __attribute__((packed));
 
 struct vis_packet {
 	uint8_t  packet_type;
 	uint8_t  version;        /* batman version field */
 	uint8_t  vis_type;	 /* which type of vis-participant sent this? */
-	uint8_t  seqno;		 /* sequence number */
 	uint8_t  entries;	 /* number of entries behind this struct */
+	uint32_t seqno;		 /* sequence number */
 	uint8_t  ttl;		 /* TTL */
 	uint8_t  vis_orig[6];	 /* originator that informs about its
 				  * neighbors */
Index: a/batman-adv-kernelland/bitarray.c
===================================================================
--- a/batman-adv-kernelland/bitarray.c	(revision 1639)
+++ a/batman-adv-kernelland/bitarray.c	(working copy)
@@ -24,10 +24,10 @@
 
 /* returns true if the corresponding bit in the given seq_bits indicates true
  * and curr_seqno is within range of last_seqno */
-uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint16_t last_seqno,
-		       uint16_t curr_seqno)
+uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint32_t last_seqno,
+		       uint32_t curr_seqno)
 {
-	int16_t diff, word_offset, word_num;
+	int32_t diff, word_offset, word_num;
 
 	diff = last_seqno - curr_seqno;
 	if (diff < 0 || diff >= TQ_LOCAL_WINDOW_SIZE) {
@@ -125,7 +125,7 @@
  *  1 if the window was moved (either new or very old)
  *  0 if the window was not moved/shifted.
  */
-char bit_get_packet(TYPE_OF_WORD *seq_bits, int16_t seq_num_diff,
+char bit_get_packet(TYPE_OF_WORD *seq_bits, int32_t seq_num_diff,
 		    int8_t set_mark)
 {
 	/* sequence number is slightly older. We already got a sequence number
Index: a/batman-adv-kernelland/bitarray.h
===================================================================
--- a/batman-adv-kernelland/bitarray.h	(revision 1639)
+++ a/batman-adv-kernelland/bitarray.h	(working copy)
@@ -26,8 +26,8 @@
 
 /* returns true if the corresponding bit in the given seq_bits indicates true
  * and curr_seqno is within range of last_seqno */
-uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint16_t last_seqno,
-					   uint16_t curr_seqno);
+uint8_t get_bit_status(TYPE_OF_WORD *seq_bits, uint32_t last_seqno,
+					   uint32_t curr_seqno);
 
 /* turn corresponding bit on, so we can remember that we got the packet */
 void bit_mark(TYPE_OF_WORD *seq_bits, int32_t n);
@@ -38,7 +38,7 @@
 
 /* receive and process one packet, returns 1 if received seq_num is considered
  * new, 0 if old  */
-char bit_get_packet(TYPE_OF_WORD *seq_bits, int16_t seq_num_diff,
+char bit_get_packet(TYPE_OF_WORD *seq_bits, int32_t seq_num_diff,
 					int8_t set_mark);
 
 /* count the hamming weight, how many good packets did we receive? */
Index: a/batman-adv-kernelland/send.c
===================================================================
--- a/batman-adv-kernelland/send.c	(revision 1639)
+++ a/batman-adv-kernelland/send.c	(working copy)
@@ -153,7 +153,7 @@
 			"%s %spacket (originator %pM, seqno %d, TQ %d, TTL %d, IDF %s) on interface %s [%s]\n",
 			fwd_str,
 			(packet_num > 0 ? "aggregated " : ""),
-			batman_packet->orig, ntohs(batman_packet->seqno),
+			batman_packet->orig, ntohl(batman_packet->seqno),
 			batman_packet->tq, batman_packet->ttl,
 			(batman_packet->flags & DIRECTLINK ?
 			 "on" : "off"),
@@ -196,7 +196,7 @@
 		bat_dbg(DBG_BATMAN,
 			"%s packet (originator %pM, seqno %d, TTL %d) on interface %s [%s]\n",
 			(forw_packet->own ? "Sending own" : "Forwarding"),
-			batman_packet->orig, ntohs(batman_packet->seqno),
+			batman_packet->orig, ntohl(batman_packet->seqno),
 			batman_packet->ttl, forw_packet->if_incoming->dev,
 			forw_packet->if_incoming->addr_str);
 
@@ -275,7 +275,8 @@
 	batman_packet = (struct batman_packet *)batman_if->packet_buff;
 
 	/* change sequence number to network order */
-	batman_packet->seqno = htons((uint16_t)atomic_read(&batman_if->seqno));
+	batman_packet->seqno =
+		htonl((uint32_t)atomic64_read(&batman_if->seqno));
 
 	if (vis_server == VIS_TYPE_SERVER_SYNC)
 		batman_packet->flags |= VIS_SERVER;
@@ -288,8 +289,7 @@
 	else
 		batman_packet->gw_flags = 0;
 
-	/* could be read by receive_bat_packet() */
-	atomic_inc(&batman_if->seqno);
+	atomic64_inc(&batman_if->seqno);
 
 	slide_own_bcast_window(batman_if);
 	send_time = own_send_time(bat_priv);
@@ -343,7 +343,7 @@
 		in_tq, tq_avg, batman_packet->tq, in_ttl - 1,
 		batman_packet->ttl);
 
-	batman_packet->seqno = htons(batman_packet->seqno);
+	batman_packet->seqno = htonl(batman_packet->seqno);
 
 	/* switch of primaries first hop flag when forwarding */
 	batman_packet->flags &= ~PRIMARIES_FIRST_HOP;
@@ -397,6 +397,7 @@
 int add_bcast_packet_to_list(struct sk_buff *skb)
 {
 	struct forw_packet *forw_packet;
+	struct bcast_packet *bcast_packet;
 	/* FIXME: each batman_if will be attached to a softif */
 	struct bat_priv *bat_priv = netdev_priv(soft_device);
 
@@ -414,6 +415,10 @@
 	if (!skb)
 		goto packet_free;
 
+	/* as we have a copy now, it is safe to decrease the TTL */
+	bcast_packet = (struct bcast_packet *)skb->data;
+	bcast_packet->ttl--;
+
 	skb_reset_mac_header(skb);
 
 	forw_packet->skb = skb;
Index: a/batman-adv-kernelland/soft-interface.c
===================================================================
--- a/batman-adv-kernelland/soft-interface.c	(revision 1639)
+++ a/batman-adv-kernelland/soft-interface.c	(working copy)
@@ -32,7 +32,7 @@
 #include <linux/etherdevice.h>
 #include "compat.h"
 
-static uint16_t bcast_seqno = 1; /* give own bcast messages seq numbers to avoid
+static uint32_t bcast_seqno = 1; /* give own bcast messages seq numbers to avoid
 				  * broadcast storms */
 static int32_t skb_packets;
 static int32_t skb_bad_packets;
@@ -214,6 +214,7 @@
 
 		bcast_packet = (struct bcast_packet *)skb->data;
 		bcast_packet->version = COMPAT_VERSION;
+		bcast_packet->ttl = TTL;
 
 		/* batman packet type: broadcast */
 		bcast_packet->packet_type = BAT_BCAST;
@@ -223,7 +224,7 @@
 		memcpy(bcast_packet->orig, mainIfAddr, ETH_ALEN);
 
 		/* set broadcast sequence number */
-		bcast_packet->seqno = htons(bcast_seqno);
+		bcast_packet->seqno = htonl(bcast_seqno);
 
 		/* broadcast packet. on success, increase seqno. */
 		if (add_bcast_packet_to_list(skb) == NETDEV_TX_OK)
Index: a/batman-adv-kernelland/hard-interface.c
===================================================================
--- a/batman-adv-kernelland/hard-interface.c	(revision 1639)
+++ a/batman-adv-kernelland/hard-interface.c	(working copy)
@@ -261,7 +261,7 @@
 	batman_if->if_status = IF_INACTIVE;
 	orig_hash_add_if(batman_if, bat_priv->num_ifaces);
 
-	atomic_set(&batman_if->seqno, 1);
+	atomic64_set(&batman_if->seqno, 1);
 	printk(KERN_INFO "batman-adv:Adding interface: %s\n", batman_if->dev);
 
 	if (hardif_is_iface_up(batman_if))
Index: a/batman-adv-kernelland/routing.c
===================================================================
--- a/batman-adv-kernelland/routing.c	(revision 1639)
+++ a/batman-adv-kernelland/routing.c	(working copy)
@@ -323,7 +323,7 @@
  *  0 if the packet is to be accepted
  *  1 if the packet is to be ignored.
  */
-static int window_protected(int16_t seq_num_diff,
+static int window_protected(int32_t seq_num_diff,
 				unsigned long *last_reset)
 {
 	if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE)
@@ -357,7 +357,7 @@
 	struct orig_node *orig_node;
 	struct neigh_node *tmp_neigh_node;
 	char is_duplicate = 0;
-	int16_t seq_diff;
+	int32_t seq_diff;
 	int need_update = 0;
 	int set_mark;
 
@@ -526,7 +526,7 @@
 	char is_my_addr = 0, is_my_orig = 0, is_my_oldorig = 0;
 	char is_broadcast = 0, is_bidirectional, is_single_hop_neigh;
 	char is_duplicate;
-	unsigned short if_incoming_seqno;
+	uint32_t if_incoming_seqno;
 
 	/* Silently drop when the batman packet is actually not a
 	 * correct packet.
@@ -544,7 +544,7 @@
 		return;
 
 	/* could be changed by schedule_own_packet() */
-	if_incoming_seqno = atomic_read(&if_incoming->seqno);
+	if_incoming_seqno = atomic64_read(&if_incoming->seqno);
 
 	has_directlink_flag = (batman_packet->flags & DIRECTLINK ? 1 : 0);
 
@@ -1124,7 +1124,7 @@
 	struct bcast_packet *bcast_packet;
 	struct ethhdr *ethhdr;
 	int hdr_size = sizeof(struct bcast_packet);
-	int16_t seq_diff;
+	int32_t seq_diff;
 	unsigned long flags;
 
 	/* drop packet if it has not necessary minimum size */
@@ -1151,6 +1151,9 @@
 	if (is_my_mac(bcast_packet->orig))
 		return NET_RX_DROP;
 
+	if (bcast_packet->ttl < 2)
+		return NET_RX_DROP;
+
 	spin_lock_irqsave(&orig_hash_lock, flags);
 	orig_node = ((struct orig_node *)
 		     hash_find(orig_hash, bcast_packet->orig));
@@ -1163,12 +1166,12 @@
 	/* check whether the packet is a duplicate */
 	if (get_bit_status(orig_node->bcast_bits,
 			   orig_node->last_bcast_seqno,
-			   ntohs(bcast_packet->seqno))) {
+			   ntohl(bcast_packet->seqno))) {
 		spin_unlock_irqrestore(&orig_hash_lock, flags);
 		return NET_RX_DROP;
 	}
 
-	seq_diff = ntohs(bcast_packet->seqno) - orig_node->last_bcast_seqno;
+	seq_diff = ntohl(bcast_packet->seqno) - orig_node->last_bcast_seqno;
 
 	/* check whether the packet is old and the host just restarted. */
 	if (window_protected(seq_diff, &orig_node->bcast_seqno_reset)) {
@@ -1179,7 +1182,7 @@
 	/* mark broadcast in flood history, update window position
 	 * if required. */
 	if (bit_get_packet(orig_node->bcast_bits, seq_diff, 1))
-		orig_node->last_bcast_seqno = ntohs(bcast_packet->seqno);
+		orig_node->last_bcast_seqno = ntohl(bcast_packet->seqno);
 
 	spin_unlock_irqrestore(&orig_hash_lock, flags);
 	/* rebroadcast packet */
Index: a/batman-adv-kernelland/aggregation.c
===================================================================
--- a/batman-adv-kernelland/aggregation.c	(revision 1639)
+++ a/batman-adv-kernelland/aggregation.c	(working copy)
@@ -254,9 +254,9 @@
 	while (aggregated_packet(buff_pos, packet_len,
 				 batman_packet->num_hna)) {
 
-		/* network to host order for our 16bit seqno, and the
+		/* network to host order for our 32bit seqno, and the
 		   orig_interval. */
-		batman_packet->seqno = ntohs(batman_packet->seqno);
+		batman_packet->seqno = ntohl(batman_packet->seqno);
 
 		hna_buff = packet_buff + buff_pos + BAT_PACKET_LEN;
 		receive_bat_packet(ethhdr, batman_packet,
Index: a/batman-adv-kernelland/main.h
===================================================================
--- a/batman-adv-kernelland/main.h	(revision 1639)
+++ a/batman-adv-kernelland/main.h	(working copy)
@@ -69,7 +69,7 @@
 #define MAX_AGGREGATION_MS 100
 
 #define RESET_PROTECTION_MS 30000
-#define EXPECTED_SEQNO_RANGE	4096
+#define EXPECTED_SEQNO_RANGE	65536
 /* don't reset again within 30 seconds */
 
 #define MODULE_INACTIVE 0