On 2 December 2016 at 20:39, Hannes Frederic Sowa <han...@stressinduktion.org> wrote:
Hey, > E.g. you can use IP addresses bound to other interfaces to send replys > on another interface. This can be useful if you have a limited amount of > IP addresses on the system but much more interfaces. Especially if they > are limited in scope, like in IPv6. > > Basically Cisco's feature of "unnumbered interface" is always provided > in Linux. And there are certainly cases where you would want to use it, > e.g. emulate private-vlan feature for network separation. Got it, thanks, the explanation makes sense. And indeed it's valid case, but also it is the exception, not the rule. I think it would be entirely change the default and people who want 'unnumbered' style behaviour (like some BRAS scenarios), will know how to and why to configure it. > Also in the BGP setup, you might have it easier to establish loopback > neighbor contact by just using static on-link routes, without caring > about more complex numbering there (otherwise you pretty soon introduce > OSPF or some other routing protocol to do the recursive forward resolution). The BGP is running on-link, it's just that the BGP is advertising loop of Linux. Why the loop ends up in ND cache, I don't know. >> Grand, not that I feel comfortable writing it. I'd rather see the >> whole suppression functionality moved to neighbour.c from being AFI >> specific. > > Yes sure, please provide a patch. A separate sysctl is necessary anyway > because the current one is within the ipv4 procfs directory hierarchy. Sorry, not a comfortable C programmer, I'm pretty confident I could get it working, but I'm more confident that patch would be entirely rejected and rewritten by someone who knows what they are doing. I see no reason not to have AFI specific toggle, just logic and code should be AFI agnostic, like GC (ARP/ND cache time) stuff in neighbour.c is nicely done. Frankly whole ARP/ND code could do with refactoring to make arp.c and ndisc.c more wire-format stuff and behavioural code more in neighbour.c. -- ++ytti
