What causes "http proxy host can't parsed. %s %s" in XX-net/XX-Net?

Fix the client to send a valid 'Host: host[:port]' header on every proxied HTTP/1.1 request.

http proxy host can't parsed. %s %s

Error message

http proxy host can't parsed. %s %s

What it means

While handling an absolute-form or proxy-style HTTP request, x_tunnel's http_handler could not find a Host header (or could not parse one into host/port via netloc_to_host_port). The proxy needs the destination host before it can create an outbound connection, so it logs the request line and header block and returns 'HTTP/1.1 500 Fail' to the client.

Source

Thrown at code/default/x_tunnel/local/proxy_handler.py:369

            p = url[7:].find(b"/")
            if p >= 0:
                path = url[7+p:]
            else:
                path = b"/"
        else:
            header_block = self.read_headers()
            lines = header_block.split(b"\r\n")
            path = url
            host = None
            headers = {}
            for line in lines:
                key, _, value = line.partition(b":")
                headers[key] = value
                if key.lower() == b"host":
                    host, port = netloc_to_host_port(value)
            if host is None:
                xlog.warn("http proxy host can't parsed. %s %s", req_line, header_block)
                self.connection.send(b'HTTP/1.1 500 Fail\r\n\r\n')
                return

            if url.startswith(b"/openai/"):
                content_length = int(headers.get(b"Content-Length", 0))
                req_body = self.read_bytes(content_length)
                return openai_handler.handle_openai(method, url, headers, req_body, self.connection)

        sock = self.connection
        conn_id = proxy_session.create_conn(sock, host, port)
        if not conn_id:
            xlog.warn("http create conn to %s:%d fail", host, port)
            sock.send(b'HTTP/1.1 500 Fail\r\n\r\n')
            return

        xlog.info("http %r connect to %s:%d conn:%d", self.client_address, host, port, conn_id)

        new_req_line = b"%s %s %s" % (method, path, http_version)

View on GitHub (pinned to cfa5bc17b6)

Solutions

Fix the client to send a valid 'Host: host[:port]' header on every proxied HTTP/1.1 request.
Check the logged req_line/header_block in the warning to see exactly what the client sent and which header is missing or malformed.
If you control the client, prefer origin-form requests with an explicit proxy (absolute URI) so the target can be taken from the request line.
As a defensive improvement, fall back to parsing the host out of an absolute-form URL when the Host header is absent.

Example fix

# before
request = b'GET / HTTP/1.1\r\n\r\n'  # no Host header

# after
request = b'GET / HTTP/1.1\r\nHost: example.com\r\n\r\n'

Defensive patterns

Strategy: validation

Validate before calling

# before proxying, validate the request has a parseable Host
host_header = headers.get(b'Host') or headers.get(b'host')
if not host_header:
    conn.send(b'HTTP/1.1 400 Bad Request\r\n\r\n')
else:
    proxy.http_handler(req)

Prevention

Always send a Host header in HTTP/1.1 requests through the proxy.
Validate outgoing request headers in client code before writing to the socket.

When it happens

Trigger: A client sends an HTTP/1.1 request through the local proxy without a Host header (HTTP/1.0-style client), or with a malformed Host value (e.g. 'Host: :8080', empty value, or non-ASCII bytes) that netloc_to_host_port cannot split into host and port.

Common situations: Legacy HTTP/1.0 tools or custom sockets that omit Host; health-check probes (e.g. 'GET / HTTP/1.0') from load balancers; malformed hand-written raw requests in tests; clients sending Host with a value that has no port and breaks the parser.

Related errors

AI-assisted analysis of XX-net/XX-Net@cfa5bc17b6 (2026-08-27). Data as JSON: /api/errors/96c003348cad0376. Report an issue: GitHub.