From 09c25d1f6cea196a0c6c4128e839a3402f60308c Mon Sep 17 00:00:00 2001 From: Fu Siyuan Date: Fri, 8 Jul 2016 11:59:13 +0800 Subject: [PATCH] NetworkPkg: Fix bug in TCP which not sending out ACK in certain circumstance. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Consider the situation as shown in below chart. The last ACK message has acknowledged the Tcb->RcvWl2, and all the segments until Tcb->RcvNxt have been received by TCP driver. The Tcb->RcvNxt is not acknowledged due to the delayed ACK. In this case an incoming segment (Seg->Seq, Seg->End) should not be accepted by TCP driver, and an immediate ACK is required. Current TcpSeqAcceptable() thought it’s an acceptable segment incorrectly, it continues the TcpInput() process instead of sending out an ACK and droping the segment immediately. Tcb->RcvWl2 Tcb->RcvNxt Tcb->RcvWl2 + Tcb->RcvWnd Seg->Seq Seg->End | | | | | | | ---+-----+---------------+-------------+--------------------------+----------- <----Acceptable Range--- --> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Fu Siyuan Reviewed-By: Eugene Cohen Reviewed-By: Wu Jiaxin Reviewed-By: Ye Ting --- NetworkPkg/TcpDxe/TcpInput.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/NetworkPkg/TcpDxe/TcpInput.c b/NetworkPkg/TcpDxe/TcpInput.c index 745ee4cc6e..28bb021d7e 100644 --- a/NetworkPkg/TcpDxe/TcpInput.c +++ b/NetworkPkg/TcpDxe/TcpInput.c @@ -31,7 +31,7 @@ TcpSeqAcceptable ( IN TCP_SEG *Seg ) { - return (TCP_SEQ_LEQ (Tcb->RcvWl2, Seg->End) && + return (TCP_SEQ_LEQ (Tcb->RcvNxt, Seg->End) && TCP_SEQ_LT (Seg->Seq, Tcb->RcvWl2 + Tcb->RcvWnd)); } -- 2.39.2