net_sched: better precise estimation on packet length for untrusted packets

net_sched: better precise estimation on packet length for untrusted packets

[ Upstream commit 15e5a030716468dce4032fa0f398d840fa2756f6 ]

gso_segs were reset to zero when kernel receive packets from untrusted
source. But we use this zero value to estimate precise packet len which is
wrong. So this patch tries to estimate the correct gso_segs value before using
it in qdisc_pkt_len_init().

Signed-off-by: Jason Wang <jasowang@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>