This is a note to let you know that I've just added the patch titled hdlc_ppp: carrier detect ok, don't turn off negotiation to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: hdlc_ppp-carrier-detect-ok-don-t-turn-off-negotiation.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Mar 8 10:22:29 PST 2018 From: Denis Du <dudenis2000@xxxxxxxx> Date: Sat, 24 Feb 2018 16:51:42 -0500 Subject: hdlc_ppp: carrier detect ok, don't turn off negotiation 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; Patches currently in stable-queue which might be from dudenis2000@xxxxxxxx are queue-4.4/hdlc_ppp-carrier-detect-ok-don-t-turn-off-negotiation.patch