This removes two ambiguities in employing the new definition of before48,
following the analysis on
http://www.mail-archive.com/dccp@vger.kernel.org/msg01295.html
(1) Updating GSR when P.seqno >= S.SWL
With the old definition we did not update when P.seqno and S.SWL are 2^47
apart. To
ensure the same behaviour as with the old definition, this is replaced
with the
equivalent condition dccp_delta_seqno(S.SWL, P.seqno) >= 0
(2) Sending SYNC when P.seqno >= S.OSR
Here it is debatable whether the new definition causes an ambiguity: the
case is
similar to (1); and to have consistency with the case (1), we use the
equivalent
condition dccp_delta_seqno(S.OSR, P.seqno) >= 0
Detailed Justification
----------------------
dccp_delta_seqno(a, b) returns a value >= 0 if either a is `before' b or a ==
b,
using the new definition: a `before' b <=> 1 <= (b - a) mod 2^48 <= 2^47 -
1.
The old and new definition of `before' are identical as long as the modulo-2^48
difference between a and b is not equal to 2^47. In both cases, a test of the
form !before(x, y) has been replaced by dccp_delta_seqno(y, x) >= 0.
For all values excluding y = (x + 2^47) % 2^48, the equivalence is clear to
see.
When y = (x + 2^47) % 2^48 then !before(x, y) returned false in the new
definition.
However, 'dccp_delta_seqno(x, (x+2^47) % 2^48) >= 0' also returns false; hence
we
have full equivalence.
Signed-off-by: Gerrit Renker <[EMAIL PROTECTED]>
Acked-by: Ian McDonald <[EMAIL PROTECTED]>
Signed-off-by: Arnaldo Carvalho de Melo <[EMAIL PROTECTED]>
---
net/dccp/input.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 78b043c..a190015 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -86,7 +86,8 @@ static int dccp_check_seqno(struct sock *sk, struct sk_buff
*skb)
dh->dccph_type == DCCP_PKT_SYNCACK) {
if (between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
dp->dccps_awl, dp->dccps_awh) &&
- !before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_swl))
+ dccp_delta_seqno(dp->dccps_swl,
+ DCCP_SKB_CB(skb)->dccpd_seq) >= 0)
dccp_update_gsr(sk, DCCP_SKB_CB(skb)->dccpd_seq);
else
return -1;
@@ -203,7 +204,8 @@ static int __dccp_rcv_established(struct sock *sk, struct
sk_buff *skb,
if (dp->dccps_role != DCCP_ROLE_CLIENT)
goto send_sync;
check_seq:
- if (!before48(DCCP_SKB_CB(skb)->dccpd_seq, dp->dccps_osr)) {
+ if (dccp_delta_seqno(dp->dccps_osr,
+ DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
send_sync:
dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
DCCP_PKT_SYNC);
--
1.5.0.3
-
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