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>
diff --git a/net/dccp/options.c b/net/dccp/options.c
index f4ff0a3..5adeeed 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -429,9 +429,10 @@
{
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 @@
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 @@
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;
}
