[CCID2]: Sequence number wraparound issues

This replaces several uses of standard arithmetic with the DCCP
sequence number arithmetic functions. The problem here is that the
sequence number wrap-around was not taken into consideration.

 * Condition "seqp->ccid2s_seq <= prev->ccid2s_seq" has been replaced
   by

   	dccp_delta_seqno(seqp->ccid2s_seq, prev->ccid2s_seq) >= 0

   since if seqp is `before' prev, then the delta_seqno() is positive.

 * The test whether sequence numbers `a' and `b' are consecutive has
   the form

   	dccp_delta_seqno(a, b) == 1

 * Increment of ccid2hctx_rpseq could be done using dccp_inc_seqno(),
   but since here the incremented ccid2hctx_rpseq == seqno, used
   assignment instead.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 1dff4188f3f5..426008e3b7e3 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -59,7 +59,8 @@ static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
                                 pipe++;
 
                         /* packets are sent sequentially */
-                        BUG_ON(seqp->ccid2s_seq <= prev->ccid2s_seq);
+                        BUG_ON(dccp_delta_seqno(seqp->ccid2s_seq,
+                                                prev->ccid2s_seq ) >= 0);
                         BUG_ON(time_before(seqp->ccid2s_sent,
                                            prev->ccid2s_sent));
 
@@ -562,8 +563,8 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 hctx->ccid2hctx_rpseq = seqno;
         } else {
                 /* check if packet is consecutive */
-                if ((hctx->ccid2hctx_rpseq + 1) == seqno)
-                        hctx->ccid2hctx_rpseq++;
+                if (dccp_delta_seqno(hctx->ccid2hctx_rpseq, seqno) == 1)
+                        hctx->ccid2hctx_rpseq = seqno;
                 /* it's a later packet */
                 else if (after48(seqno, hctx->ccid2hctx_rpseq)) {
                         hctx->ccid2hctx_rpdupack++;