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在 Mac OS X 上我的 TIME_WAIT 在哪里？

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在 Mac OS X 上我的 TIME_WAIT 在哪里？

TIME_WAITMac OS X 上没有

正常情况下，当一个TCP连接关闭时，最先被调用一侧的socketclose()会保持该TIME_WAIT状态。

当其中一个对等点是 Mac OS X (Lion) 计算机时TIME_WAIT，netstat -an如果close()if在 Mac 端首先调用。然而，似乎套接字是实际上处于TIME_WAIT状态，因为尝试再次调用listen()（不使用套接字选项SO_REUSEADDR）导致listen()失败。

等待 2*MSL（最大段生命周期，在 Mac OS X Lion 上为 15 秒，报告sysctl net.inet.tcp.msl）清除TIME_WAIT状态，并且listen()可以再次调用而不会出现错误。

为何我看不到插座TIME_WAIT？

测试

以下是两个简单的 Python 测试程序。

服务器

#!/usr/bin/env python

import socket

HOST = ''
PORT = 50007
l = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
l.bind((HOST, PORT))
l.listen(1)
print("Listening on %d" % PORT)
(s, _) = l.accept()
print("Connected")
raw_input("Press <enter> to close...")
l.close()
s.close()
print("Closed")

客户

#!/usr/bin/env python

import socket
import sys

HOST = sys.argv[1]
PORT = 50007

print("Opening connection to server")
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
raw_input("Press <enter> to close...")
s.close()
print("Closed")

当在两台不同的 Linux 机器上同时运行服务器和客户端时，首先按下<enter>呼叫的一方会获得预期的结果：close()TIME_WAIT

$ ./server-timewait.py 
Listening on 50007
Connected
Press <enter> to close...
Closed
$ netstat -an | grep 50007
tcp        0      0 172.16.185.219:50007    172.16.185.42:49818     TIME_WAIT  
$

当其中一个对等体是 Mac（运行 OS X Lion）时，我从未在 Mac 上看到过在先关闭后TIME_WAIT运行时的情况。netstat -an | grep 50007

答案1

这错误报告声称问题出在 netstat执行。错误报告附带的代码正确显示了处于 TIME_WAIT 状态的套接字。您需要删除以下几行

if (lip == INADDR_LOCALHOST ||
  lip == INADDR_ANY
  ) { continue; }

使其显示绑定到本地主机的套接字。

答案2

这不是一个答案，但有人也许能够从中挖掘出更多信息。

tcpdump -i lo0 -vv port 50007

## Press Enter at the server window

# Server send a FIN (note the flag)
23:33:04.283768 IP (tos 0x0, ttl 64, id 4134, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->2c9c)!)
    localhost.50007 > localhost.56030: Flags [F.], cksum 0xfe28 (incorrect -> 0xeff9), seq 1, ack 1, win 9186, options [nop,nop,TS val 432165676 ecr 432157913], length 0

# Client send back ACK
23:33:04.283803 IP (tos 0x0, ttl 64, id 44906, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->8d57)!)
    localhost.56030 > localhost.50007: Flags [.], cksum 0xfe28 (incorrect -> 0xd1a6), seq 1, ack 2, win 9186, options [nop,nop,TS val 432165676 ecr 432165676], length 0

# Server confirm the ACK is received
23:33:04.283812 IP (tos 0x0, ttl 64, id 18284, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->f555)!)
    localhost.50007 > localhost.56030: Flags [.], cksum 0xfe28 (incorrect -> 0xd1a6), seq 2, ack 1, win 9186, options [nop,nop,TS val 432165676 ecr 432165676], length 0

## After this point, the server process is actually exit but client still running.
## It's strange that re-run server script gives "OSError: [Errno 48] Address already in use"
## and netstat shows this connection is in CLOSE_WAIT status

## Press Enter at the client window

# Client send a FIN to server
23:33:09.731728 IP (tos 0x0, ttl 64, id 51478, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->73ab)!)
    localhost.56030 > localhost.50007: Flags [F.], cksum 0xfe28 (incorrect -> 0xbcb6), seq 1, ack 2, win 9186, options [nop,nop,TS val 432171035 ecr 432165676], length 0

# WTH!? Who send back this packet? The server process is closed!
23:33:09.731764 IP (tos 0x0, ttl 64, id 18754, offset 0, flags [DF], proto TCP (6), length 52, bad cksum 0 (->f37f)!)
    localhost.50007 > localhost.56030: Flags [.], cksum 0xfe28 (incorrect -> 0xa7c7), seq 2, ack 2, win 9186, options [nop,nop,TS val 432171035 ecr 432171035], length 0

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