[Dnsmasq-discuss] DHCP packet received on <interface> which has no address

Simon Kelley simon at thekelleys.org.uk
Sun Aug 28 18:17:23 BST 2016


On 25/08/16 11:32, Andrew Shadura wrote:
> On 25/08/16 13:26, Andrew Shadura wrote:
>> Okay, let me give you a more specific example, with just one of the
>> interfaces.
>>
>> Let's say we've got eth0 with vlans:
>>   eth0.1, static config
>>   eth0.2, static config + dhcp server
>>   eth0.3, dhcp client
> 
> So, let's say we've configured eth0.1 and eth0.2, then started dnsmasq.
>  It complains eth3.4 (an interface expected on a different machine)
> doesn't exist, so it'll skip and ignore it, and then it starts listening
> on eth0.2.
> 
> Next, we bring eth0.3 up. DHCP client starts, and then dnsmasq starts
> complaining it's received a DHCP packet on eth0.3 it didn't expect.
> 
> As I can see in the code, the first thing dnsmasq does for a packet
> received on some interface is that it attempts to determine the
> interface address. If that fails, none of the checks, which are further
> down in the code, are performed.

This is definitely a real bug. This patch should fix it, and apply
easily to earlier versions, if you so wish.

http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=e94ad0fa01ccc8d0c39e069ab29b008f9c811600


Cheers,

Simon.





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