net/interfaces: ensure we return valid 'self' IP in LikelyHomeRouterIP

Before this fix, LikelyHomeRouterIP could return a 'self' IP that
doesn't correspond to the gateway address, since it picks the first
private address when iterating over the set interfaces as the 'self' IP,
without checking that the address corresponds with the
previously-detected gateway.

This behaviour was introduced by accident in aaf2df7, where we deleted
the following code:

    for _, prefix := range privatev4s {
        if prefix.Contains(gateway) && prefix.Contains(ip) {
            myIP = ip
            ok = true
            return
        }
    }

Other than checking that 'gateway' and 'ip' were private IP addresses
(which were correctly replaced with a call to the netip.Addr.IsPrivate
method), it also implicitly checked that both 'gateway' and 'ip' were a
part of the *same* prefix, and thus likely to be the same interface.

Restore that behaviour by explicitly checking pfx.Contains(gateway),
which, given that the 'ip' variable is derived from our prefix 'pfx',
ensures that the 'self' IP will correspond to the returned 'gateway'.

Fixes #10466

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Iddd2ee70cefb9fb40071986fefeace9ca2441ee6

0 files changed, 0 insertions, 0 deletions