Shared Conn

Passing a net.Conn between processes.

Intro

Toy program meant to address this go forum issue.

This program creates a listener by binding to the supplied address, accesses the underlying FD, and passes it to a child process.

The child process recreates the listener using the shared FD, then attempts to rebind the same address as the parent.

It exposes two issues via command line flags.

Setup

go get github.com/jdhenke/shared-conn

Usage

$ shared-conn -h
Usage of shared-conn:
  -addr string
    	address on which to listen (default ":1234")
  -ignoreFiles
    	ignore closing FDs
  -triggerRace
    	trigger race condition

Example

Running with default settings should pass, although a race exists.

$ shared-conn
parent | 17:36:02.190679 Using address=`:1234`
parent | 17:36:02.193514 Closed listener.
parent | 17:36:02.193528 Closed file.
child  | 17:36:02.196729 Using address=`:1234`
child  | 17:36:02.196920 Closed listener.
child  | 17:36:02.196929 Closed file.
child  | 17:36:02.196931 Rebinding...
child  | 17:36:02.196983 PASS
parent | 17:36:02.197860 PASS

Running with trigger race should fail, although a race exists.

$ shared-conn -triggerRace
parent | 17:36:08.220841 Using address=`:1234`
child  | 17:36:08.226717 Using address=`:1234`
child  | 17:36:08.226917 Closed listener.
child  | 17:36:08.226921 Closed file.
child  | 17:36:08.226922 Rebinding...
child  | 17:36:08.226972 Child could not recreate listener: listen tcp :1234: bind: address already in use
parent | 17:36:10.226090 Closed listener.
parent | 17:36:10.226135 Closed file.
parent | 17:36:10.226188 Child process error: exit status 1

Leaving the files open then attempting to rebind should always fail.

$ shared-conn -ignoreFiles
parent | 17:36:14.632811 Using address=`:1234`
parent | 17:36:14.635907 Closed listener.
child  | 17:36:14.638920 Using address=`:1234`
child  | 17:36:14.639092 Closed listener.
child  | 17:36:14.639095 Rebinding...
child  | 17:36:14.639142 Child could not recreate listener: listen tcp :1234: bind: address already in use
parent | 17:36:14.639982 Child process error: exit status 1