[FS#388] odhcpd: A default route is present but there is no public prefix on br-lan thus we don't an

[LEDE Bugs]

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FS#388 - odhcpd: A default route is present but there is no public prefix on br-lan thus we don't an
User who did this - Dave Täht (dtaht)

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OK, I have narrowed it down still further - taking  the local pd attempt out of the loop. Down to just the one comcast modem - lede router - one linux client. As to *why* ipv6 was working at all, *all this time*, for anyone on comcast (or this particular modem) my linux box will see a retraction, and its expires timer will run to -30 seconds, then expire. And odhcp almost always gets a new one out there in roughly a minute. (except when getting flooded or other problems that I was triggering that made it more obvious!).

The "not announcing" thing we started with was a symptom... I think. Even with ra_default 1 I'm still watching my ra on the client appear and disappear. Attached are two tcpdumps the dhcpv6 one is what I'm seeing from comcast, the local-comcast one is what I'm sending internally.

tcpdump -i br-lan -w /tmp/local-comcast.cap icmp6 or udp port 546 or udp port 547

packet 17 makes things go bye-bye, packet 38 brings things back to life. 

Mon Jan 16 17:25:47 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:25:50 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:25:53 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:25:54 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:25:55 2017 daemon.debug odhcpd[1074]: Received 72 Bytes from kernel%netlink
Mon Jan 16 17:25:55 2017 daemon.debug odhcpd[1074]: Received 116 Bytes from kernel%netlink
Mon Jan 16 17:25:55 2017 daemon.debug odhcpd[1074]: Received 136 Bytes from kernel%netlink
Mon Jan 16 17:25:55 2017 daemon.debug odhcpd[1074]: Received 136 Bytes from kernel%netlink

# Something happened here. Also the route to the main ULA disappears

lorna-gw: # fdaf:dc63:6de9:8::/64 via fe80::822a:a8ff:fe86:3417 dev br-lan  proto static  metric 1024  pref medium vanishes
# and there is no fe80::822a:a8ff:fe86:3417? The switch?

Mon Jan 16 17:25:55 2017 daemon.info dnsmasq[4724]: read /etc/hosts - 4 addresses
Mon Jan 16 17:25:55 2017 daemon.info dnsmasq[4724]: read /tmp/hosts/odhcpd - 0 addresses
Mon Jan 16 17:25:55 2017 daemon.info dnsmasq[4724]: read /tmp/hosts/dhcp.cfg02411c - 4 addresses
Mon Jan 16 17:25:55 2017 daemon.info dnsmasq-dhcp[4724]: read /etc/ethers - 0 addresses
Mon Jan 16 17:25:55 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:25:56 2017 daemon.debug odhcpd[1074]: Sent 64 bytes to ff02::1%br-lan

# and this sends that short ra packet presumably retracting everything and my expires timer starts counting down 0, -1, -2 ...

Mon Jan 16 17:25:57 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:25:58 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:25:58 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:00 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:01 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:01 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:03 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:07 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:11 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:14 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:17 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:20 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:22 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:22 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:23 2017 daemon.debug odhcpd[1074]: Received 88 Bytes from kernel%netlink
Mon Jan 16 17:26:24 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:25 2017 daemon.debug odhcpd[1074]: Received 72 Bytes from kernel%netlink
Mon Jan 16 17:26:25 2017 daemon.debug odhcpd[1074]: Received 116 Bytes from kernel%netlink
Mon Jan 16 17:26:27 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:27 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:27 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:28 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:31 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:34 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:34 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:34 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:37 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:41 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:44 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:48 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:50 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:51 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:54 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0
Mon Jan 16 17:26:55 2017 daemon.debug odhcpd[1074]: Received 72 Bytes from kernel%netlink
Mon Jan 16 17:26:55 2017 daemon.debug odhcpd[1074]: Received 116 Bytes from kernel%netlink
Mon Jan 16 17:26:55 2017 daemon.debug odhcpd[1074]: Received 136 Bytes from kernel%netlink
Mon Jan 16 17:26:55 2017 daemon.debug odhcpd[1074]: Received 136 Bytes from kernel%netlink
Mon Jan 16 17:26:55 2017 daemon.info dnsmasq[4724]: read /etc/hosts - 4 addresses
Mon Jan 16 17:26:55 2017 daemon.info dnsmasq[4724]: read /tmp/hosts/odhcpd - 1 addresses
Mon Jan 16 17:26:55 2017 daemon.info dnsmasq[4724]: read /tmp/hosts/dhcp.cfg02411c - 4 addresses
Mon Jan 16 17:26:55 2017 daemon.info dnsmasq-dhcp[4724]: read /etc/ethers - 0 addresses
Mon Jan 16 17:26:56 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:56 2017 daemon.debug odhcpd[1074]: Received 76 Bytes from kernel%netlink
Mon Jan 16 17:26:56 2017 daemon.debug odhcpd[1074]: Sent 176 bytes to ff02::1%br-lan
Mon Jan 16 17:26:58 2017 daemon.debug odhcpd[1074]: Received 144 Bytes from fe80::201:5cff:fe63:e446%eth0

And then we're back!


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https://bugs.lede-project.org/index.php?do=details&task_id=388#comment1283