感谢大佬的帮助，不过还是没找到具体问题，还在努力探索中

@GYY_顽石: 建议看一下tcp stream

@dudu:    因为我做的是SIP通讯，看起来像是这个问题，不过这个ICMP报的错不一致啊，我在看看吧

@dudu: 附地址：https://tools.ietf.org/html/rfc3261#section-18.1.1

@GYY_顽石: 建议看一下8.1.3.1

8.1.3.1 Transaction Layer Errors
In some cases, the response returned by the transaction layer will
not be a SIP message, but rather a transaction layer error. When a
timeout error is received from the transaction layer, it MUST be
treated as if a 408 (Request Timeout) status code has been received.
If a fatal transport error is reported by the transport layer
(generally, due to fatal ICMP errors in UDP or connection failures in
TCP), the condition MUST be treated as a 503 (Service Unavailable)
status code.

@dudu:  好像是对端的实现有问题，看RFC解释是 sip 的 数据大小最大是限制在 1300 以内的 （MTU - 200) 。哎，看他们怎么解释吧。

The Session Initiation Protocol (SIP) mandates a maximum size for any request transmitted over UDP. This maximum is set to the lesser of 1300 bytes or the path maximum transmission unit (MTU) size minus 200 bytes. If the size of the request exceeds this maximum, SIP requires implementations to switch the downstream transport to be a congestion  controlled transport. However, when sending a response, a SIP implementation cannot choose the transport; it must use the transport specified by the Via. This document discusses the problems large responses can cause on UDP, and proposes an update to SIP to help diagnose and avoid those problems.