dccp ccid-2: Implementation of circular Ack Vector buffer with overflow handling

This completes the implementation of a circular buffer for Ack Vectors, by
extending the current (linear array-based) implementation.  The changes are:

 (a) An `overflow' flag to deal with the case of overflow. As before, dynamic
     growth of the buffer will not be supported; but code will be added to deal
     robustly with overflowing Ack Vector buffers.

 (b) A `tail_seqno' field. When naively implementing the algorithm of Appendix A
     in RFC 4340, problems arise whenever subsequent Ack Vector records overlap,
     which can bring the entire run length calculation completely out of synch.
     (This is documented on http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/\
                                             ack_vectors/tracking_tail_ackno/ .)
 (c) The buffer length is now computed dynamically (i.e. current fill level),
     as the span between head to tail.

As a result, dccp_ackvec_pending() is now simpler - the #ifdef is no longer
necessary since buf_empty is always true when IP_DCCP_ACKVEC is not configured.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

1 files changed, 7 insertions, 4 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index a8ed459508b2..19fafd597465 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -457,12 +457,15 @@ static inline void dccp_update_gss(struct sock *sk, u64 seq)
 	dp->dccps_awh = dp->dccps_gss;
 }
 
+static inline int dccp_ackvec_pending(const struct sock *sk)
+{
+	return dccp_sk(sk)->dccps_hc_rx_ackvec != NULL &&
+	       !dccp_ackvec_is_empty(dccp_sk(sk)->dccps_hc_rx_ackvec);
+}
+
 static inline int dccp_ack_pending(const struct sock *sk)
 {
-	const struct dccp_sock *dp = dccp_sk(sk);
-	return (dp->dccps_hc_rx_ackvec != NULL &&
-		dccp_ackvec_pending(dp->dccps_hc_rx_ackvec)) ||
-	       inet_csk_ack_scheduled(sk);
+	return dccp_ackvec_pending(sk) || inet_csk_ack_scheduled(sk);
 }
 
 extern int  dccp_feat_finalise_settings(struct dccp_sock *dp);