From 21a265c0d1ef93ed40e1990f33be0bc427e956f0 Mon Sep 17 00:00:00 2001
From: Sean Edmond <seanedmond@linux.microsoft.com>
Date: Wed, 4 Jan 2023 18:16:26 -0800
Subject: [PATCH] net: tftp: Fix for DATA ACK for block count out of order
In rfc7440, if an ACK is not received by the server or if the
last data block in a window is dropped, the server will timeout and
retransmit the window. In this case, the block count received will be
less than the internal block count. In this case, the client
should not ACK. ACK should only be sent if the received block
count is greater than the expected block count.
Signed-off-by: Sean Edmond <seanedmond@linux.microsoft.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
---
net/tftp.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/tftp.c b/net/tftp.c
index c780c33f37..51e062bddf 100644
--- a/net/tftp.c
+++ b/net/tftp.c
@@ -592,6 +592,14 @@ static void tftp_handler(uchar *pkt, unsigned dest, struct in_addr sip,
debug("Received unexpected block: %d, expected: %d\n",
ntohs(*(__be16 *)pkt),
(ushort)(tftp_cur_block + 1));
+ /*
+ * Only ACK if the block count received is greater than
+ * the expected block count, otherwise skip ACK.
+ * (required to properly handle the server retransmitting
+ * the window)
+ */
+ if ((ushort)(tftp_cur_block + 1) - (short)(ntohs(*(__be16 *)pkt)) > 0)
+ break;
/*
* If one packet is dropped most likely
* all other buffers in the window
--
2.39.5