net: recognize CJDNS addresses as such

In some cases addresses come from an external source as a string or as a
`struct sockaddr_in6`, without a tag to tell whether it is a private
IPv6 or a CJDNS address. In those cases interpret the address as a CJDNS
address instead of an IPv6 address if `-cjdnsreachable` is set and the
seemingly-IPv6-address belongs to `fc00::/8`. Those external sources are:

* `-externalip=`
* `-bind=`
* UPnP
* `getifaddrs(3)` (called through `-discover`)
* `addnode`
* `connect`
* incoming connections (returned by `accept(2)`)

1 files changed, 1 insertions, 0 deletions

diff --git a/src/netaddress.h b/src/netaddress.h
index 57eb8bc72f..f074c1d3ec 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -550,6 +550,7 @@ public:
     }
 
     friend class CServiceHash;
+    friend CService MaybeFlipIPv6toCJDNS(const CService& service);
 };
 
 class CServiceHash