patch - ping select interface.

[Ralf Friedl]

Bob Keyes wrote:
> I originally made this for my own needs, contributed it to openwrt but 
> think it should go upstream to busybox. I am new here, not sure of the 
> regular way I am supposed to make contributions, but whoever is in charge 
> of accepting patches please take a look at 
> https://dev.openwrt.org/ticket/2522 which will explain the rational for 
> the feature and includes the patch for it.
>
> Regards,
> Bob Keyes
Can you explain how this is different from option -I ? From the man page 
of the linux ping:
-I interface address
Set source address to specified interface address. Argument may be 
numeric IP address  or  name  of  device.
When pinging IPv6 link-local address this option is required.

It seems the -I is supposed to accept either an IP address or a device 
name. I suggest to keep it compatible.

Regards
Ralf Friedl