[Dnsmasq-discuss] No DHCP leases handed on bridge interface

Simon Kelley simon at thekelleys.org.uk
Sat Jul 16 23:08:44 BST 2016


On 16/07/16 12:16, Albert ARIBAUD wrote:

> Alright... I'm out of ideas, sorry -- apart from recompiling dnsmasq
> with ad hoc debug code. :/
> 

I can't see anything obvious from what's been posted so far, but it
might be worth pointing out that this arrangement is used in millions of
openWRT routers and has been for years. Ie my openWRT router looks like


root at melaleuca:~# brctl show
bridge name	bridge id		STP enabled	interfaces
br-lan		7fff.e4956e4061cc	no		eth1
							wlan0

root at melaleuca:~# ifconfig
br-lan    Link encap:Ethernet  HWaddr E4:95:6E:40:61:CC
          inet addr:192.168.150.1  Bcast:192.168.150.255  Mask:255.255.255.0
          inet6 addr: fd66:67b7:4126::1/60 Scope:Global
          inet6 addr: fe80::e695:6eff:fe40:61cc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3009106 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3571295 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:390966486 (372.8 MiB)  TX bytes:3069836286 (2.8 GiB)

.
.
eth1      Link encap:Ethernet  HWaddr E4:95:6E:40:61:CC
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:5

.
.
wlan0     Link encap:Ethernet  HWaddr E4:95:6E:40:61:CC
          inet6 addr: fe80::e695:6eff:fe40:61cc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3029316 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3576669 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:436550756 (416.3 MiB)  TX bytes:3129854122 (2.9 GiB)


And has a dhcp-range line in the config

dhcp-range=lan,192.168.150.100,192.168.150.249,255.255.255.0,12h


and it just works.


Note that ISC dhcpd uses a very low level code to access packets,
bypassing the whole of the kernel network stack and iptables. It
essentially does the same as tcpdump or wireshark. Dnsmasq doesn't, it
uses the kernel network stack. That may be a clue as to why ISC works
but dnsmasq doesn't, especially the iptables bit. The usual problem is
dumping packets with destination 255.255.255.255 or packets with source
0.0.0.0


Cheers,

Simon.




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