Re: Subtleties of the 0.0.0.0 netmask (inet_ifa_match)

[Allen Lau]

Alexey,

>> The inet_ifa_match function seems to be wrong with 0.0.0.0 netmask.
>...
>> The 0.0.0.0 netmask matches everything!
>
>Of course. Zero mask matches everything.

I agree that 0.0.0.0 netmask in a route entry (dest 0.0.0.0 mask 0.0.0.0)
matches everything.
However, it is intuitively different with an interface address.
Can an IP address be on every subnet (i.e. is 10.1.1.1 prefix 0 on every
subnet)?

I believe it is not right for inet_ifa_match to answer "yes" in the context of :
     is 9.9.9.9 on the same subnet as interface address 10.1.1.1 prefix 0?

>> Will there be any routing problems if we use the 0.0.0.0 netmask?
>
>No problems provided you wanted this.
>F.e. default route is route with netmask zero, it matches all,
>so that all the addresses are routed there.
>It is exactly which happens in your setup, but all the addresses
>fall to loopback.

>Looking at your original purpose, you wanted mask 255.255.255.255.

>Alexey

Allen Lau