From: Eric Dumazet <edumazet@google.com>
Date: Sat, 20 Oct 2018 02:11:26 +0000 (-0700)
Subject: net: loopback: clear skb->tstamp before netif_rx()
X-Git-Tag: v4.19.2~313
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3fdf483bcf76ab19cf4412c6cac31135d7eda30e;p=platform%2Fkernel%2Flinux-rpi.git

net: loopback: clear skb->tstamp before netif_rx()

[ Upstream commit 4c16128b6271e70c8743178e90cccee147858503 ]

At least UDP / TCP stacks can now cook skbs with a tstamp using
MONOTONIC base (or arbitrary values with SCM_TXTIME)

Since loopback driver does not call (directly or indirectly)
skb_scrub_packet(), we need to clear skb->tstamp so that
net_timestamp_check() can eventually resample the time,
using ktime_get_real().

Fixes: 80b14dee2bea ("net: Add a new socket option for a future transmit time.")
Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 3061249..d192936 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -75,6 +75,10 @@ static netdev_tx_t loopback_xmit(struct sk_buff *skb,
 	int len;
 
 	skb_tx_timestamp(skb);
+
+	/* do not fool net_timestamp_check() with various clock bases */
+	skb->tstamp = 0;
+
 	skb_orphan(skb);
 
 	/* Before queueing this packet to netif_rx(),