Dropping reply received on <downstream interface> when using -iu/-id

[Brian J. Murrell]

On Wed, 2018-01-03 at 00:47 +0100, Patrick Cervicek wrote:
> 
> To me it looks like DHCP Offer did come in via br-guest (and not br-
> lan)

Which is not right.

> Are this interfaces seperated or somehow bridged together?

They are separate.  No bridging between them.  They themselves are
bridges but not together:

# brctl show
bridge name	bridge id		STP enabled	interfaces
br-guest	7fff.f250d105d430	no		eth0.15
							wlan1-1
							wlan0-1
br-lan		7fff.6cb0cef51e4a	no		eth0.1
							wlan1
							wlan0

> Locally or on the same switch/vlan

I think I know where you are going and I would tend to hold bridge
and/or vlan leaks among the lowest of probabilities of causes here.  I
seem to recall tcpdump showing me that DHCP packets were moving in the
correct directions also.

> The server should be reachable only via br-lan

Right.  It is.

> Could you provide:
> brctl show br-guest
> brctl show br-lan

As above.

> ip addr 

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether f2:50:d1:05:d4:30 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::f050:d1ff:fe05:d430/64 scope link 
       valid_lft forever preferred_lft forever
6: br-guest: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether f2:50:d1:05:d4:30 brd ff:ff:ff:ff:ff:ff
    inet 192.168.101.252/24 brd 192.168.101.255 scope global br-guest
       valid_lft forever preferred_lft forever
    inet 192.168.101.254/24 brd 192.168.101.255 scope global secondary br-guest
       valid_lft forever preferred_lft forever
    inet6 fe80::f050:d1ff:fe05:d430/64 scope link 
       valid_lft forever preferred_lft forever
7: eth0.15 at eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-guest state UP group default qlen 1000
    link/ether f2:50:d1:05:d4:30 brd ff:ff:ff:ff:ff:ff
8: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 6c:b0:ce:f5:1e:4a brd ff:ff:ff:ff:ff:ff
    inet 10.75.22.252/24 brd 10.75.22.255 scope global br-lan
       valid_lft forever preferred_lft forever
    inet 10.75.22.254/24 scope global secondary br-lan
       valid_lft forever preferred_lft forever
    inet6 fe80::6eb0:ceff:fef5:1e4a/64 scope link 
       valid_lft forever preferred_lft forever
9: eth0.1 at eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP group default qlen 1000
    link/ether 6c:b0:ce:f5:1e:4a brd ff:ff:ff:ff:ff:ff
12: wlan1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP group default qlen 1000
    link/ether 6c:b0:ce:f5:1e:4c brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6eb0:ceff:fef5:1e4c/64 scope link 
       valid_lft forever preferred_lft forever
14: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-lan state UP group default qlen 1000
    link/ether 6c:b0:ce:f5:1e:4a brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6eb0:ceff:fef5:1e4a/64 scope link 
       valid_lft forever preferred_lft forever
16: wlan1-1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-guest state UP group default qlen 1000
    link/ether 6e:b0:ce:f5:1e:4c brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6cb0:ceff:fef5:1e4c/64 scope link 
       valid_lft forever preferred_lft forever
17: wlan0-1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-guest state UP group default qlen 1000
    link/ether 6e:b0:ce:f5:1e:4a brd ff:ff:ff:ff:ff:ff
    inet6 fe80::6cb0:ceff:fef5:1e4a/64 scope link 
       valid_lft forever preferred_lft forever

Cheers,
b.
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