IfaceMgr::getIface types

Hello, IfaceMgr::getIface may have some incorrect types. This may be related to issues #1825 (closed) and #2027.

I'm giving Kea a very quick check as part of the Ubuntu Main Inclusion Review process, and part of that is a Coverity scan. Coverity has identified this comparison as not depending upon the inputs:

(ifindex > std::numeric_limits<int32_t>::max())

IfacePtr
IfaceMgr::getIface(int ifindex) {
    if ((ifindex < 0) || (ifindex > std::numeric_limits<int32_t>::max())) {
        return (IfacePtr()); // out of range
    }
    return (ifaces_.getIface(ifindex));
}

https://gitlab.isc.org/isc-projects/kea/-/blob/master/src/lib/dhcp/iface_mgr.cc#L903

If the bounds really are "non-negative integers", then it's probably fine. But it seemed plausible to me that the types were intended to be different, so, this report.

Thanks