Re: [PATCH] gre6: Fix reception with IP6_TNL_F_RCV_DSCP_COPY

From: Mark Tomlinson <redacted>
Date: Wed, 19 Aug 2020 13:53:58 +1200

When receiving an IPv4 packet inside an IPv6 GRE packet, and the
IP6_TNL_F_RCV_DSCP_COPY flag is set on the tunnel, the IPv4 header would
get corrupted. This is due to the common ip6_tnl_rcv() function assuming
that the inner header is always IPv6. This patch checks the tunnel
protocol for IPv4 inner packets, but still defaults to IPv6.

Fixes: 308edfdf1563 ("gre6: Cleanup GREv6 receive path, call common GRE functions")
Signed-off-by: Mark Tomlinson <redacted>

Applied and queued up for -stable, thank you.