Re: tcp: disallow bind() to reuse addr/port regression in 2.6.38

[Eric Dumazet <eric.dumazet@gmail.com>]

Le samedi 02 avril 2011 à 20:01 +0200, Cyril Bonté a écrit :
> Hi All,
> 
> (2nd try to fix the mailing list address)
> 
> It has been reported that kernel 2.6.38 prevented the load balancer haproxy to 
> reload. After reading the kernel Changelog, it looks like the following commit 
> has a negative side effect on the the way haproxy "pauses" its listening 
> sockets to start a new process :
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c191a836a908d1dd6b40c503741f91b914de3348
> 
> Disabling the TCPF_CLOSE flag condition reallows to work as before. I guess 
> this was done for good reasons (Sorry, I haven't found the thread about that 
> commit in the archives yet) but other applications may also be impacted by 
> this change.
> 
> I add Willy Tarreau to the CC to open the discussion.
> 

> 		if (shutdown(listenfd, SHUT_WR) == 0 &&
> 		    listen(listenfd, 1024) == 0 &&
> 		    shutdown(listenfd, SHUT_RD) == 0) {
> 			printf("shutdown OK\n");
> 		}
> 	}
> 	exit(0);
> }
> 

Wow, not clear what this is doing.... 

for sure the listen() call is not needed ?

And the shutdown(listenfd, SHUT_WR) is clearly useless too.

I feel you only needed the shutdown(listenfd, SHUT_RD) call.

Why haproxy needs to setup a second listening socket on same port ?