Merge lp:~mpontillo/squid-deb-proxy/possible-ipv6-fix into lp:squid-deb-proxy

[Mike Pontillo]

Qualify IPv6 link-local addresses with interface scope.

This is a (possible) fix for the "link-local addresses unusable with apt" issue that was noted in the source code to apt-avahi-discover.

In most cases (even when only one interface exists on the system), IPv6 link-local addresses are not usable unless scoped with an interface name. See RFC 4007 section 11 for more details.[1]

Linux uses interface names as zone_id values, so all we need to do (in theory) is append "%<interface-name>" to the link-local address.

I have not tested this yet, but I am in the process of setting up an IPv6-only test environment due to a customer requirement, so I may get a chance to test it in the coming weeks/months.

[1]:
https://tools.ietf.org/html/rfc4007#section-11

Unmerged revisions

141. By Mike Pontillo on 2016-05-10

Qualify link-local addresses with interface scope.

=== modified file 'apt-avahi-discover'
--- apt-avahi-discover	2013-09-20 08:04:12 +0000
+++ apt-avahi-discover	2016-05-10 05:42:18 +0000
@@ -83,10 +83,12 @@
             addr = tokens[7]
             port = int(tokens[8])
             if is_ipv6(addr):
-                # We need to skip ipv6 link-local addresses since 
-                # APT can't use them
-                if not is_linklocal(addr):
-                    addr6.append((addr, port))
+                # Link-local IPv6 addresses must be scoped by interface,
+                # otherwise they are not usable.
+                if is_linklocal(addr):
+                    iface = tokens[1]
+                    addr = "{addr}%{iface}".format(addr=addr, iface=iface)
+                addr6.append((addr, port))
             else:
                 addr4.append((addr, port))