[utils.inc] [is_linklocal()] Invalid LL recognition code

[eshield]

Hi,

While working on correct dynamic gateway creation algo I've noticed the subject function which is implemented as:

return (strtolower(substr($ipaddr, 0, 5)) == "fe80:");

I believe this code will fail to recognise LL address in some cases because LL scope has a /10 prefix … so even "fe81:" is a correct LL address will be counted as invalid.

After some research I've noticed that this code affects the following functions in case of [FE81..FEBF] LL addresses:
[interfaces.inc] interface_configure() - Will remove all valid LL addresses on all interfaces;
[interfaces.inc] find_interface_ipv6_ll() - Will never find first LL address on the interface;
[services.inc] services_dnsmasq_configure() - dnsmasq will be unable to bind on valid LL address;
[system.inc] system_routing_configure() - Routing will not be properly configured because scope won't be added if LL address is not FE80;
[gwlb.inc] setup_gateways_monitor() - Gateway monitors will not be properly configured if LL address is not FE80;

I will post a pull request soon with fix for the subject along with some fixes for dynamic gateways, but I think this fix should be merged to 2.1 branch too. Yeah, this bug is not that sensitive but you never know what can\could\will happen  :)