Function send_early_hints

gunicorn/http/wsgi.py:140–183

Send 103 Early Hints response. Args: headers: List of (name, value) header tuples, typically Link headers Example: [('Link', '</style.css>; rel=preload; as=style')] Raises: InvalidHeaderName: If a header name is not a valid HTTP token.

(headers)

        - Calls after response has started are silently ignored
    """
    def send_early_hints(headers):
        """Send 103 Early Hints response.

        Args:
            headers: List of (name, value) header tuples, typically Link headers
                     Example: [('Link', '</style.css>; rel=preload; as=style')]

        Raises:
            InvalidHeaderName: If a header name is not a valid HTTP token.
            InvalidHeader: If a header value contains invalid characters.
        """
        # Don't send after response has started - would break framing
        if resp.headers_sent:
            return

        # Don't send to HTTP/1.0 clients - they don't support 1xx responses
        if req.version < (1, 1):
            return

        # Build 103 response
        response = b"HTTP/1.1 103 Early Hints\r\n"
        for name, value in headers:
            if isinstance(name, bytes):
                name = name.decode('latin-1')
            if isinstance(value, bytes):
                value = value.decode('latin-1')

            # Validate header name and value using the same checks as
            # Response.process_headers — defense-in-depth against
            # HTTP response splitting via CRLF injection.
            if not TOKEN_RE.fullmatch(name):
                raise InvalidHeaderName('%r' % name)
            if not HEADER_VALUE_RE.fullmatch(value):
                # Pass only the name — the invalid value may contain
                # sensitive data that shouldn't cross security boundaries
                # via exception propagation (browsers/proxies may forward
                # it to untrusted parties).
                raise InvalidHeader('%r' % name)

            value = value.strip(" \t")
            response += f"{name}: {value}\r\n".encode('latin-1')
        response += b"\r\n"

        util.write(sock, response)

    return send_early_hints