dccp: fix error in updating the GAR

This fixes a bug in updating the Greatest Acknowledgment number Received (GAR):
the current implementation does not track the greatest received value -
lower values in the range AWL..AWH (RFC 4340, 7.5.1) erase higher ones.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/dccp/input.c b/net/dccp/input.c
index 265985370fa1..e424a09e83f6 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -239,7 +239,8 @@ static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
                 dccp_update_gsr(sk, seqno);
 
                 if (dh->dccph_type != DCCP_PKT_SYNC &&
-                    (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
+                    ackno != DCCP_PKT_WITHOUT_ACK_SEQ &&
+                    after48(ackno, dp->dccps_gar))
                         dp->dccps_gar = ackno;
         } else {
                 unsigned long now = jiffies;