7. 错误码

Error codes are 32-bit fields that are used in RST_STREAM and GOAWAY frames to convey the reasons for the stream or connection error.

错误码是32位字段，用在RST_STREAM和超时帧中去标识流或者连接错误的原因。

Error codes share a common code space. Some error codes apply only to either streams or the entire connection and have no defined semantics in the other context.

错误码共享一个代码空间。 一些错误码仅仅适用于其中的一些流或者整个连接，在其他的情况下并没有明确的意义。

The following error codes are defined:

错误码有如下定义：

• NO_ERROR (0x0): The associated condition is not a result of an error. For example, a GOAWAY might include this code to indicate graceful shutdown of a connection.
• PROTOCOL_ERROR (0x1): The endpoint detected an unspecific protocol error. This error is for use when a more specific error code is not available.
• INTERNAL_ERROR (0x2): The endpoint encountered an unexpected internal error.
• FLOW_CONTROL_ERROR (0x3): The endpoint detected that its peer violated the flow-control protocol.
• SETTINGS_TIMEOUT (0x4): The endpoint sent a SETTINGS frame but did not receive a response in a timely manner. See Section 6.5.3 ("Settings Synchronization").
• STREAM_CLOSED (0x5): The endpoint received a frame after a stream was half-closed.
• FRAME_SIZE_ERROR (0x6): The endpoint received a frame with an invalid size.
• REFUSED_STREAM (0x7): The endpoint refused the stream prior to performing any application processing (see Section 8.1.4 for details).
• CANCEL (0x8): Used by the endpoint to indicate that the stream is no longer needed.
• COMPRESSION_ERROR (0x9): The endpoint is unable to maintain the header compression context for the connection.
• CONNECT_ERROR (0xa): The connection established in response to a CONNECT request (Section 8.3) was reset or abnormally closed.
• ENHANCE_YOUR_CALM (0xb): The endpoint detected that its peer is exhibiting a behavior that might be generating excessive load.
• INADEQUATE_SECURITY (0xc): The underlying transport has properties that do not meet minimum security requirements (see Section 9.2).
• HTTP_1_1_REQUIRED (0xd): The endpoint requires that HTTP/1.1 be used instead of HTTP/2.

• NO_ERROR(0x0): 相关环境不作为错误处理。 例如： 超时帧可能包含该错误码来表明连接的正常关闭。
• PROTOCOL_ERROR (0x1)： 终端检测到一个不确定性质的协议错误。 这个错误码用在一个更加确切的错误码不可用的情况下。
• INTERNAL_ERROR (0x2)： 终端遇到了一个意外的内部错误。
• FLOW_CONTROL_ERROR (0x3)： 终端检测到对等端违背了流量控制协议。
• SETTINGS_TIMEOUT (0x4)： 终端发送了一个设置帧，但是没有在指定时间内得到响应。 参见Section 6.5.3 ("Settings Synchronization")。
• STREAM_CLOSED (0x5)： 终端在流的半封闭状态接收到了帧。
• FRAME_SIZE_ERROR (0x6)： 终端接收到一个超出最大尺寸的帧。
• REFUSED_STREAM (0x7)： 终端拒绝流之前执行了程序处理。 参见Section 8.1.4。
• CANCEL (0x8): 标识这个流不再是需要的。
• COMPRESSION_ERROR (0x9)： 终端无法维护报头压缩上下文的连接。
• CONNECT_ERROR (0xa)： 为响应一个连接请求的而建立的连接参见：Section 8.3被重置或者异常关闭。
• ENHANCE_YOUR_CALM (0xb)： 终端检测到其对等端的某行为可能负荷超载。
• INADEQUATE_SECURITY (0xc)： 底层传输特性不符合最低安全要求。 参见 Section 9.2。
• HTTP_1_1_REQUIRED (0xd)： 终端应该使用HTTP/1.1, 而不是HTTP/2。

Unknown or unsupported error codes MUST NOT trigger any special behavior. These MAY be treated by an implementation as being equivalent to INTERNAL_ERROR.

未知或者不支持的错误码绝不会触发任何特殊的行为。 它们可能会被当做内部错误（INTERNAL_ERROR）来处理。