Hello 2All,

Recently I had written to the list about KPs I've been experiencing with
OpenWRT-based firmwares built from trunk on DIR-615 E4. That time system hadn't
been able to sustain uptime longer than ~2 hours. It had been fixed in r28213
thx to Frédéric Moulins report and trac ticket #10071. Using firmware build from
r28222 I've got around 5 days uptime without any obvious trouble.

Yesterday I had finally managed to find some time to start configuring the box
to do the real work - I was going to use it as a simple AP for a couple of days.
Unfortunately things hadn't come out as expected.

After disabling dnsmasq dhcp server functionality, setting up fixed fixed IP for
"lan" iface, connecting LAN1 port of the box to the existing LAN infrastructure
and configuring wifi (it is ath9k for this board) things seemed to work pretty
well for several hours and then I had lost connectivity to the box from the LAN
side. It was possible to associate with the box from WiFi side but there were no
connectivity between WiFi and LAN (i.e. br-lan bridge hadn't been working as it
should).

My first "solution" was to simply power cycle the box. It rebooted and
connectivity restored. As I had too power cycle it the contents of
/sys/kernel/debug/crashlog were emply and I had no clue about what had gone
wrong. It didn't took long for connectivity to be lost again - this time box had
worked normally for only about 6 hours.

Quick investigations showed the following:

a) WiFi was functioning OK and I was able to SSH into the box from my laptop
after manually setting IP/subnet;

b) Re-connecting ethernet wire from LAN1 port into WAN worked as expected: box
requested IP for itself from local dhcp server and (after minor changes to the
routing table as br-lan and wan subnets resulted to be the same differing only
by IP) I was able to ssh into the box from "outside";

c) Inspecting dmesg showed that the actual problem was with eth0 port
flip-flopping beetween up/down state on its own as soon as I connect wire with
active link to any LAN port of the box. It looks like this:

......
Jan  1 23:52:44 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:44 OpenWrt kern.info kernel: eth0: link up (1000Mbps/Full duplex)
Jan  1 23:52:44 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:44 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:44 OpenWrt kern.info kernel: eth0: link down
Jan  1 23:52:45 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:45 OpenWrt kern.info kernel: eth0: link up (1000Mbps/Full duplex)
Jan  1 23:52:45 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:45 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:45 OpenWrt kern.info kernel: eth0: link down
Jan  1 23:52:45 OpenWrt kern.info kernel: eth0: link up (1000Mbps/Full duplex)
Jan  1 23:52:46 OpenWrt kern.info kernel: eth0: link down
Jan  1 23:52:47 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:47 OpenWrt kern.info kernel: eth0: link up (1000Mbps/Full duplex)
Jan  1 23:52:47 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
Jan  1 23:52:47 OpenWrt kern.info kernel: br-lan: port 1(eth0) entering
forwarding state
......

d) It was sufficient to do simple /etc/init.d/network restart to bring the eth0
port back into working state.

e) While the port was flip-flopping I had tried to play a bit with
swconfig/mii-tool/ethtool over eth0 without any success. mii-tool had been
unable to read/change anything for this interface, the only info ethtool had
been able to read was the flip-flopping link state. Any changes to switch
configuration through swconfig resulted in no effect: enabling/disabling vlan,
defining/removing separate vlans, e.t.c.

Would try to play a bit more with swconfig/brctl/vconfig as soon as I would hit
this bug again. Any suggestions about how to hunt this nasty down? Anybody else
having similar problems on DIR-600/601 or DIR-615 E3/E4 boards?

-- 
Best regards,
Alexey Loukianov                          mailto:[email protected]
System Engineer,                            Mob.:+7(926)218-1320
*nix Specialist


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