From 92d64c261e77cb2a6117887617e2a629fea6b67c Mon Sep 17 00:00:00 2001 From: Schoch Christian Date: Wed, 28 Nov 2012 05:18:29 +0000 Subject: [PATCH] sctp: Error in calculation of RTTvar The calculation of RTTVAR involves the subtraction of two unsigned numbers which may causes rollover and results in very high values of RTTVAR when RTT > SRTT. With this patch it is possible to set RTOmin = 1 to get the minimum of RTO at 4 times the clock granularity. Change Notes: v2) *Replaced abs() by abs64() and long by __s64, changed patch description. Signed-off-by: Christian Schoch CC: Vlad Yasevich CC: Sridhar Samudrala CC: Neil Horman CC: linux-sctp@vger.kernel.org Acked-by: Vlad Yasevich Acked-by: Neil Horman Signed-off-by: David S. Miller --- net/sctp/transport.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sctp/transport.c b/net/sctp/transport.c index 953c21e..206cf52 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -331,7 +331,7 @@ void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt) * 1/8, rto_alpha would be expressed as 3. */ tp->rttvar = tp->rttvar - (tp->rttvar >> net->sctp.rto_beta) - + ((abs(tp->srtt - rtt)) >> net->sctp.rto_beta); + + (((__u32)abs64((__s64)tp->srtt - (__s64)rtt)) >> net->sctp.rto_beta); tp->srtt = tp->srtt - (tp->srtt >> net->sctp.rto_alpha) + (rtt >> net->sctp.rto_alpha); } else { -- 2.7.4