Link-local address handling for IPv4

Link-local address handling for IPv4

[Fischer, Anna]

Hi,

Does the Linux kernel network stack do any specific handling of link-local address configuration and handling according to RFC 3927? I know that there is user-level code like Zeroconf / Avahi and these tools create ARP sockets directly on the specified network interfaces in order to support link-local address handling. But if I do not run any of these tools, does the kernel's ARP code take care of this, too?

Thanks,
Anna

Re: Link-local address handling for IPv4

[Eric Dumazet]

Le mardi 22 juin 2010 à 13:17 +0000, Fischer, Anna a écrit :
> Hi,
> 
> Does the Linux kernel network stack do any specific handling of 

> link-local address configuration and handling according to RFC 3927?

>  I know that there is user-level code like Zeroconf / Avahi and these

>  tools create ARP sockets directly on the specified network interfaces 

> in order to support link-local address handling. But if I do not 

> run any of these tools, does the kernel's ARP code take care of this, too?
> 

There is no RFC 3927 support in kernel, you need user space support (or
switch to DHCP ;) )

Note that ARP replies MUST also be broadcasted for this particular
169.254/16 network (RFC 3927, 2.5), you need a kernel patch too, this
was discussed 4 years ago on netdev, and nothing was decided/changed.

http://marc.info/?l=linux-netdev&m=114427223811197&w=2


BTW I believe that our forwarding path doesnt test source/destination
address not being part of 169.254/16 network, I am not sure it
is a real problem or not. A netfilter rule can fix it eventually.

7.  Router Considerations

   A router MUST NOT forward a packet with an IPv4 Link-Local source or
   destination address, irrespective of the router's default route
   configuration or routes obtained from dynamic routing protocols.

   A router which receives a packet with an IPv4 Link-Local source or
   destination address MUST NOT forward the packet.  This prevents
   forwarding of packets back onto the network segment from which they
   originated, or to any other segment.