4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Denis Du <dudenis2000@xxxxxxxx> [ Upstream commit b6c3bad1ba83af1062a7ff6986d9edc4f3d7fc8e ] Sometimes when physical lines have a just good noise to make the protocol handshaking fail, but the carrier detect still good. Then after remove of the noise, nobody will trigger this protocol to be start again to cause the link to never come back. The fix is when the carrier is still on, not terminate the protocol handshaking. Signed-off-by: Denis Du <dudenis2000@xxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/wan/hdlc_ppp.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/drivers/net/wan/hdlc_ppp.c +++ b/drivers/net/wan/hdlc_ppp.c @@ -574,7 +574,10 @@ static void ppp_timer(unsigned long arg) ppp_cp_event(proto->dev, proto->pid, TO_GOOD, 0, 0, 0, NULL); proto->restart_counter--; - } else + } else if (netif_carrier_ok(proto->dev)) + ppp_cp_event(proto->dev, proto->pid, TO_GOOD, 0, 0, + 0, NULL); + else ppp_cp_event(proto->dev, proto->pid, TO_BAD, 0, 0, 0, NULL); break;