[LEDE-DEV] IPv6 link locals, vlans and bridging

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Fri Aug 25 06:16:22 PDT 2017 

Here's a 'fun' one that I'm trying to work who is doing what incorrectly.

For 'reasons' I have a number of tagged vlan ethernet interfaces.  I 
also have a similar number of wifi interfaces.  These vlan ethernet 
interfaces and wifi interfaces are bridged together in pairs.

The wifi interfaces have non-unique link local addresses that appear 
auto assigned:

wlan0     Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:4E
           inet6 addr: fe80::62e3:27ff:feaf:9e4e/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:43577 errors:0 dropped:0 overruns:0 frame:0
           TX packets:82723 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:15588069 (14.8 MiB)  TX bytes:97978594 (93.4 MiB)

wlan0-1   Link encap:Ethernet  HWaddr 62:E3:27:AF:9E:4E
           inet6 addr: fe80::60e3:27ff:feaf:9e4e/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15106 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:0 (0.0 B)  TX bytes:7953093 (7.5 MiB)

wlan1     Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:4F
           inet6 addr: fe80::62e3:27ff:feaf:9e4f/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:90 errors:0 dropped:0 overruns:0 frame:0
           TX packets:16399 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:12498 (12.2 KiB)  TX bytes:8373520 (7.9 MiB)

wlan1-1   Link encap:Ethernet  HWaddr 62:E3:27:AF:9E:4F
           inet6 addr: fe80::60e3:27ff:feaf:9e4f/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15748 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:0 (0.0 B)  TX bytes:8266015 (7.8 MiB)

The ethernet vlans mostly do not have link local addresses except eth1.3 
which is the main untagged and hence main interface (this also has a 
global address)

eth1.10   Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:39845 errors:0 dropped:0 overruns:0 frame:0
           TX packets:69474 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:5739889 (5.4 MiB)  TX bytes:65964032 (62.9 MiB)

eth1.15   Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:3 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15786 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:319 (319.0 B)  TX bytes:7995298 (7.6 MiB)

eth1.20   Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:29258 errors:0 dropped:0 overruns:0 frame:0
           TX packets:50498 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:2799288 (2.6 MiB)  TX bytes:36024938 (34.3 MiB)

eth1.25   Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:3 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15782 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:319 (319.0 B)  TX bytes:7994866 (7.6 MiB)

eth1.3    Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           inet addr:192.250.219.1  Bcast:192.168.250.255 
Mask:255.255.255.0
           inet6 addr: fe80::62e3:27ff:feaf:9e50/64 Scope:Link
           inet6 addr: 2a02:c7f:1250:1250::da2b:da2b/64 Scope:Global
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:8254319 errors:0 dropped:0 overruns:0 frame:0
           TX packets:5455240 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:12101826609 (11.2 GiB)  TX bytes:325616404 (310.5 MiB)

So far, possibly so good.  The 'fun' starts with the bridge interfaces:

br-wifi5_guest Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           inet addr:192.168.25.1  Bcast:192.168.25.255  Mask:255.255.255.0
           inet6 addr: 2a02:c7f:1234:bf25::da2b:da2b/64 Scope:Global
           inet6 addr: fe80::62e3:27ff:feaf:9e50/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:3 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15782 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:319 (319.0 B)  TX bytes:7994866 (7.6 MiB)

br-wifi5_priv Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           inet addr:192.168.20.1  Bcast:192.168.20.255  Mask:255.255.255.0
           inet6 addr: 2a02:c7f:1234:bf20::da2b:da2b/64 Scope:Global
           inet6 addr: fe80::62e3:27ff:feaf:9e50/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:72837 errors:0 dropped:0 overruns:0 frame:0
           TX packets:113739 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:17777291 (16.9 MiB)  TX bytes:123549133 (117.8 MiB)

br-wifi_guest Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           inet addr:192.168.15.1  Bcast:192.168.15.255  Mask:255.255.255.0
           inet6 addr: fe80::62e3:27ff:feaf:9e50/64 Scope:Link
           inet6 addr: 2a02:c7f:1234:bf15::da2b:da2b/64 Scope:Global
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:3 errors:0 dropped:0 overruns:0 frame:0
           TX packets:15786 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:319 (319.0 B)  TX bytes:7995298 (7.6 MiB)

br-wifi_priv Link encap:Ethernet  HWaddr 60:E3:27:AF:9E:50
           inet addr:192.168.10.1  Bcast:192.168.10.255  Mask:255.255.255.0
           inet6 addr: fe80::62e3:27ff:feaf:9e50/64 Scope:Link
           inet6 addr: 2a02:c7f:1234:bf10::da2b:da2b/64 Scope:Global
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:39937 errors:0 dropped:0 overruns:0 frame:0
           TX packets:69501 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:5751139 (5.4 MiB)  TX bytes:65973138 (62.9 MiB)

You will note that they all have the same link local address.  I 
honestly don't know if that's legal or not, but let's move on to the 
problem.

I have dnsmasq listening on the bridge interfaces - it's happy doing so 
and says it's listening on the link local address (effectively the same 
address many times) all ok.  It also listens on the global address.  If 
I configure dns clients to use the link local address for DNS service I 
get no responses.  If I configure dns clients to use the global address 
relevant for each bridge then dns responses are fine.

I suspect that dnsmasq is receiving the requests but is unable to 
reply....goes to enable some logging to test that a bit later...

Who is doing what incorrectly here?

Cheers,

Kevin

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