I've installed OpenWrt SNAPSHOT r14572-4682d4d770 / LuCI Master git-20.267.56601-1da9df8 and i get this:
[ 790.720339] eth1: link down
[ 791.745505] eth1: link up (100Mbps/Full duplex)
[ 794.194461] pppoe-wan: renamed from ppp0
[ 971.968709] eth1: link down
[ 972.993213] eth1: link up (100Mbps/Full duplex)
[ 975.587036] pppoe-wan: renamed from ppp0
[ 1538.267864] eth1: link down
[ 1539.292891] eth1: link up (100Mbps/Full duplex)
[ 1548.508562] eth1: link down
[ 1549.532822] eth1: link up (100Mbps/Full duplex)
[ 1833.178748] eth1: link down
[ 1834.203839] eth1: link up (100Mbps/Full duplex)
[ 1848.538941] eth1: link down
[ 1849.563800] eth1: link up (100Mbps/Full duplex)
[ 2795.732121] eth1: link down
[ 2796.757379] eth1: link up (100Mbps/Full duplex)
[ 2906.323568] eth1: link down
[ 2907.348841] eth1: link up (100Mbps/Full duplex)
[ 3686.050181] ath10k_pci 0000:00:00.0: Invalid VHT mcs 15 peer stats
[ 3776.715198] eth1: link down
[ 3777.740258] eth1: link up (100Mbps/Full duplex)
[ 3922.121018] eth1: link down
[ 3923.146277] eth1: link up (100Mbps/Full duplex)
[ 4291.782759] eth1: link down
[ 4292.807879] eth1: link up (100Mbps/Full duplex)
[ 4507.845399] eth1: link down
[ 4508.870594] eth1: link up (100Mbps/Full duplex)
[ 4706.500323] eth1: link down
[ 4707.525571] eth1: link up (100Mbps/Full duplex)
[ 4856.003604] eth1: link down
[ 4857.028911] eth1: link up (100Mbps/Full duplex)
[ 6745.269469] eth1: link down
[ 6746.294617] eth1: link up (100Mbps/Full duplex)
[ 6850.740632] eth1: link down
[ 6851.765968] eth1: link up (100Mbps/Full duplex)
[ 6985.908048] eth1: link down
[ 6986.933215] eth1: link up (100Mbps/Full duplex)
[ 7097.523219] eth1: link down
[ 7098.548454] eth1: link up (100Mbps/Full duplex)
and so on...
Setting "force link" on lan interface i prevent the pppoe from disconnecting all the time but some problem in the connection is noticed anyway when the lan disconnects.
Does anyone know what caused it / if it's a bug / if there is a workaround?