The following commit has been merged in the master branch: commit 22a2cfb51783bb3cf50a877dbc9d6445954c3df2 Author: Sven Eckelmann sven@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 the access to the pool has to reserve two sequence numbers in a single access. The latter one can easily be done by increasing the value of the last used sequence number by 2 in a single access. The generated window of two currently unused sequence numbers can now be scattered across the two fragments.

Reported-by: Linus Lüssing linus.luessing@web.de Signed-off-by: Sven Eckelmann sven@narfation.org

diff --git a/unicast.c b/unicast.c index ddd6852..0e7c4df 100644 --- a/unicast.c +++ b/unicast.c @@ -237,6 +237,7 @@ 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; @@ -272,10 +273,9 @@ 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);