commit 0e5bb338bf471ec46924f744c4301751bab8793a
Author: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date:   Wed May 25 14:42:07 2022 +0200

    Linux 5.15.43
    
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit d12cd0bf5d262887eeaa407744618255bde76565
Author: Mat Martineau <mathew.j.martineau@linux.intel.com>
Date:   Tue May 17 11:02:12 2022 -0700

    mptcp: Do TCP fallback on early DSS checksum failure
    
    commit ae66fb2ba6c3dcaf8b9612b65aa949a1a4bed150 upstream.
    
    RFC 8684 section 3.7 describes several opportunities for a MPTCP
    connection to "fall back" to regular TCP early in the connection
    process, before it has been confirmed that MPTCP options can be
    successfully propagated on all SYN, SYN/ACK, and data packets. If a peer
    acknowledges the first received data packet with a regular TCP header
    (no MPTCP options), fallback is allowed.
    
    If the recipient of that first data packet finds a MPTCP DSS checksum
    error, this provides an opportunity to fail gracefully with a TCP
    fallback rather than resetting the connection (as might happen if a
    checksum failure were detected later).
    
    This commit modifies the checksum failure code to attempt fallback on
    the initial subflow of a MPTCP connection, only if it's a failure in the
    first data mapping. In cases where the peer initiates the connection,
    requests checksums, is the first to send data, and the peer is sending
    incorrect checksums (see
    https://github.com/multipath-tcp/mptcp_net-next/issues/275), this allows
    the connection to proceed as TCP rather than reset.
    
    Fixes: dd8bcd1768ff ("mptcp: validate the data checksum")
    Acked-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [mathew.j.martineau: backport: Resolved bitfield conflict in protocol.h]
    Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>