WebResource.getBridgeRequestAnswer() is unhappy about IPv6 addresses
Logs on ponticum fill up with warnings about badly formed X-Forwarded-For headers. Most (all?) of them appear to be IPv6 addresses.
Bridges.is_valid_ip() recognizes IPv4 addresses only.
I don't know if extending is_valid_ip() is the right thing to do but it might. I haven't looked into other usage of it.