4 files changed, 31 insertions, 3 deletions

diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h
index 2284e8129cb2..03ce0d314c9e 100644
--- a/net/batman-adv/packet.h
+++ b/net/batman-adv/packet.h
@@ -50,6 +50,7 @@
 
 /* fragmentation defines */
 #define UNI_FRAG_HEAD 0x01
+#define UNI_FRAG_LARGETAIL 0x02
 
 struct batman_packet {
 	uint8_t  packet_type;
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 8828eddd3f72..a8cd3897b7d0 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -1193,7 +1193,7 @@ int route_unicast_packet(struct sk_buff *skb, struct batman_if *recv_if,
 				     dstaddr);
 
 	if (unicast_packet->packet_type == BAT_UNICAST_FRAG &&
-	    2 * skb->len - hdr_size <= batman_if->net_dev->mtu) {
+	    frag_can_reassemble(skb, batman_if->net_dev->mtu)) {
 
 		ret = frag_reassemble_skb(skb, bat_priv, &new_skb);
 
diff --git a/net/batman-adv/unicast.c b/net/batman-adv/unicast.c
index 811f7fc7932d..fc77079b18bb 100644
--- a/net/batman-adv/unicast.c
+++ b/net/batman-adv/unicast.c
@@ -225,6 +225,7 @@ int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
 	int uc_hdr_len = sizeof(struct unicast_packet);
 	int ucf_hdr_len = sizeof(struct unicast_frag_packet);
 	int data_len = skb->len - uc_hdr_len;
+	int large_tail = 0;
 
 	if (!bat_priv->primary_if)
 		goto dropped;
@@ -254,8 +255,11 @@ int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
 	memcpy(frag1->orig, bat_priv->primary_if->net_dev->dev_addr, ETH_ALEN);
 	memcpy(frag2, frag1, sizeof(struct unicast_frag_packet));
 
-	frag1->flags |= UNI_FRAG_HEAD;
-	frag2->flags &= ~UNI_FRAG_HEAD;
+	if (data_len & 1)
+		large_tail = UNI_FRAG_LARGETAIL;
+
+	frag1->flags = UNI_FRAG_HEAD | large_tail;
+	frag2->flags = large_tail;
 
 	frag1->seqno = htons((uint16_t)atomic_inc_return(
 			     &batman_if->frag_seqno));
diff --git a/net/batman-adv/unicast.h b/net/batman-adv/unicast.h
index e32b7867a9a4..e7211c279201 100644
--- a/net/batman-adv/unicast.h
+++ b/net/batman-adv/unicast.h
@@ -22,6 +22,8 @@
 #ifndef _NET_BATMAN_ADV_UNICAST_H_
 #define _NET_BATMAN_ADV_UNICAST_H_
 
+#include "packet.h"
+
 #define FRAG_TIMEOUT 10000	/* purge frag list entrys after time in ms */
 #define FRAG_BUFFER_SIZE 6	/* number of list elements in buffer */
 
@@ -32,4 +34,25 @@ int unicast_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv);
 int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
 		  struct batman_if *batman_if, uint8_t dstaddr[]);
 
+static inline int frag_can_reassemble(struct sk_buff *skb, int mtu)
+{
+	struct unicast_frag_packet *unicast_packet;
+	int uneven_correction = 0;
+	unsigned int merged_size;
+
+	unicast_packet = (struct unicast_frag_packet *)skb->data;
+
+	if (unicast_packet->flags & UNI_FRAG_LARGETAIL) {
+		if (unicast_packet->flags & UNI_FRAG_HEAD)
+			uneven_correction = 1;
+		else
+			uneven_correction = -1;
+	}
+
+	merged_size = (skb->len - sizeof(struct unicast_frag_packet)) * 2;
+	merged_size += sizeof(struct unicast_packet) + uneven_correction;
+
+	return merged_size <= mtu;
+}
+
 #endif /* _NET_BATMAN_ADV_UNICAST_H_ */