tcp: fix SCM_TIMESTAMPING_OPT_STATS for normal skbs

__sock_recv_timestamp can be called for both normal skbs (for
receive timestamps) and for skbs on the error queue (for transmit
timestamps).

Commit 1c885808e456
(tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING)
assumes any skb passed to __sock_recv_timestamp are from
the error queue, containing OPT_STATS in the content of the skb.
This results in accessing invalid memory or generating junk
data.

To fix this, set skb->pkt_type to PACKET_OUTGOING for packets
on the error queue. This is safe because on the receive path
on local sockets skb->pkt_type is never set to PACKET_OUTGOING.
With that, copy OPT_STATS from a packet, only if its pkt_type
is PACKET_OUTGOING.

Fixes: 1c885808e456 ("tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING")
Reported-by: JongHwan Kim <zzoru007@gmail.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
int skb_checksum_setup(struct sk_buff *skb, bool recalculate)
{
	int err;

	switch (skb->protocol) {
	case htons(ETH_P_IP):
		err = skb_checksum_setup_ipv4(skb, recalculate);
		break;

	case htons(ETH_P_IPV6):
		err = skb_checksum_setup_ipv6(skb, recalculate);
		break;

	default:
		err = -EPROTO;
		break;
	}

	return err;
}

int skb_checksum_setup(struct sk_buff *skb, bool recalculate)
{
	int err;

	switch (skb->protocol) {
	case htons(ETH_P_IP):
		err = skb_checksum_setup_ipv4(skb, recalculate);
		break;

	case htons(ETH_P_IPV6):
		err = skb_checksum_setup_ipv6(skb, recalculate);
		break;

	default:
		err = -EPROTO;
		break;
	}

	return err;
}
