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, 5 insertions, 5 deletions

diff --git a/net/dccp/options.c b/net/dccp/options.c
index f4ff0a308269..5adeeed5e0d2 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -429,9 +429,10 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 {
         struct dccp_sock *dp = dccp_sk(sk);
         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
+        const u16 buflen = dccp_ackvec_buflen(av);
         /* Figure out how many options do we need to represent the ackvec */
-        const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
-        u16 len = av->av_vec_len + 2 * nr_opts;
+        const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
+        u16 len = buflen + 2 * nr_opts;
         u8 i, nonce = 0;
         const unsigned char *tail, *from;
         unsigned char *to;
@@ -442,7 +443,7 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 
         to   = skb_push(skb, len);
-        len  = av->av_vec_len;
+        len  = buflen;
         from = av->av_buf + av->av_buf_head;
         tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
 
@@ -580,8 +581,7 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
                         if (dccp_insert_option_timestamp(skb))
                                 return -1;
 
-                } else if (dp->dccps_hc_rx_ackvec != NULL &&
-                           dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
+                } else if (dccp_ackvec_pending(sk) &&
                            dccp_insert_option_ackvec(sk, skb)) {
                                 return -1;
                 }