[linux-next] LinuxNextTracking branch, master, updated. next-20110624

batman at open-mesh.org batman at open-mesh.org
Fri Jun 24 16:08:58 CEST 2011

The following commit has been merged in the master branch:
commit c2f7f0e7b3ce55eee32892d6aa5cd88a7512ea25
Author: Sven Eckelmann <sven at narfation.org>
Date:   Thu Feb 10 14:33:56 2011 +0000

    batman-adv: Use successive sequence numbers for fragments
    The two fragments of an unicast packet must have successive sequence numbers to
    allow the receiver side to detect matching fragments and merge them again. The
    current implementation doesn't provide that property because a sequence of two
    atomic_inc_return may be interleaved with another sequence which also changes
    the variable.
    The access to the fragment sequence number pool has either to be protected by
    correct locking or it has to reserve two sequence numbers in a single fetch.
    The latter one can easily be done by increasing the value of the last used
    sequence number by 2 in a single step. The generated window of two currently
    unused sequence numbers can now be scattered across the two fragments.
    Reported-by: Linus Lüssing <linus.luessing at web.de>
    Signed-off-by: Sven Eckelmann <sven at narfation.org>

diff --git a/net/batman-adv/unicast.c b/net/batman-adv/unicast.c
index cbf022c..9b2a222 100644
--- a/net/batman-adv/unicast.c
+++ b/net/batman-adv/unicast.c
@@ -226,6 +226,7 @@ int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
 	int ucf_hdr_len = sizeof(struct unicast_frag_packet);
 	int data_len = skb->len - uc_hdr_len;
 	int large_tail = 0;
+	uint16_t seqno;
 	if (!bat_priv->primary_if)
 		goto dropped;
@@ -261,10 +262,9 @@ int frag_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv,
 	frag1->flags = UNI_FRAG_HEAD | large_tail;
 	frag2->flags = large_tail;
-	frag1->seqno = htons((uint16_t)atomic_inc_return(
-			     &batman_if->frag_seqno));
-	frag2->seqno = htons((uint16_t)atomic_inc_return(
-			     &batman_if->frag_seqno));
+	seqno = atomic_add_return(2, &batman_if->frag_seqno);
+	frag1->seqno = htons(seqno - 1);
+	frag2->seqno = htons(seqno);
 	send_skb_packet(skb, batman_if, dstaddr);
 	send_skb_packet(frag_skb, batman_if, dstaddr);


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