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HttpProxyHandler incorrectly formats IPv6 host and port in CONNECT request

See original GitHub issue

Expected behavior

The HttpProxyHandler is expected to be capable of issuing a valid CONNECT request for a tunneled connection to an IPv6 host. In this case we are passing an IPv6 address (eg fd00:c0de:42::c:293a:5736) rather than a host name.

Actual behavior

The HttpProxyHandler does not properly concatenate the IPv6 address and port. The resulting error after we fail to connect will show you the problem:

io.netty.handler.proxy.ProxyConnectException: http, none, /fd00:c0de:42:0:5:562d:d54:1:3128 => /fd00:c0de:42:0:50:5694:2fda:1:4287, status: 503 Service Unavailable

In both cases you can see the IPv6 address is formatted without brackets: fd00:c0de:42:0:50:5694:2fda:1:4287 should be [fd00:c0de:42:0:50:5694:2fda:1]:4287. This is just an exception message so it doesn’t prove it’s formatting incorrectly. However, if you look at the request on the wire you can see it is certainly wrong:

    CONNECT fd00:c0de:42:0:50:5694:2fda:1:4287 HTTP/1.1\r\n
    host: fd00:c0de:42:0:50:5694:2fda:1:4287\r\n
    \r\n

Here is the problem method from HttpProxyHandler:

    @Override
    protected Object newInitialMessage(ChannelHandlerContext ctx) throws Exception {
        InetSocketAddress raddr = destinationAddress();
        String rhost;
        if (raddr.isUnresolved()) {
            rhost = raddr.getHostString();
        } else {
            rhost = raddr.getAddress().getHostAddress();
        }

        final String host = rhost + ':' + raddr.getPort();
        FullHttpRequest req = new DefaultFullHttpRequest(
                HttpVersion.HTTP_1_1, HttpMethod.CONNECT,
                host,
                Unpooled.EMPTY_BUFFER, false);

        req.headers().set(HttpHeaderNames.HOST, host);

        if (authorization != null) {
            req.headers().set(HttpHeaderNames.PROXY_AUTHORIZATION, authorization);
        }

        return req;
    }

Specifically: final String host = rhost + ':' + raddr.getPort();

Steps to reproduce

Setup an HTTP Proxy with IPv6.
Setup a target server with an IPv6 address.
Attempt to establish a connection to the target server through the proxy, giving the HttpProxyHandler an IPv6 IP address for the target. ** We can successfully connect to the proxy server with IPv6. The problem seems to be specific to the target of the tunneled connection using an IPv6 address.