From c2f7f0e7b3ce55eee32892d6aa5cd88a7512ea25 Mon Sep 17 00:00:00 2001 From: Sven Eckelmann Date: Thu, 10 Feb 2011 14:33:56 +0000 Subject: batman-adv: Use successive sequence numbers for fragments MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Sven Eckelmann --- net/batman-adv/unicast.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'net') diff --git a/net/batman-adv/unicast.c b/net/batman-adv/unicast.c index cbf022cb312..9b2a222518f 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); -- cgit v1.2.3