Listen and IPV6 behaviour ?

[Igor Sysoev]

On Mon, Nov 09, 2009 at 07:17:24PM +0100, Jérôme Loyet wrote:

> Hi all,
> 
> How to use the nginx listen diective to listen on all interface (ipv4
> and ipv6) and on port 80 ?
> 
> I thought "listen [::]:80;" would be enought but it seems that I have
> to use both "listen 80;" and "listen [::]:80;"
> 
> Is it the normal behaviour or a bug ?
> 
> ++ Jerome
> 
> OS: OpenBSD 4.5 and linux 2.6.28
> Im' using nginx 0.8.22
> I've enable ipv6 support at compile time with --with-ipv6
> I use the default nginx conf file (just the port has been changed to 81)
> My server is fully ipv6 compliant.
> 
> If I start nginx, it listens on ipv4 only :
> listen 81;
> 
> root at wild:~/nginx-0.8.22# lsof -i :81
> COMMAND   PID   USER   FD   TYPE   DEVICE SIZE NODE NAME
> nginx   18224   root    6u  IPv6 26577575       TCP *:81 (LISTEN)
> nginx   18225 nobody    6u  IPv6 26577575       TCP *:81 (LISTEN)
> 
> If I changed the listen directive to:
> listen [::]:81;
> 
> root at wild:~/nginx-0.8.22# lsof -i :81
> COMMAND   PID   USER   FD   TYPE   DEVICE SIZE NODE NAME
> nginx   18224   root    6u  IPv6 26577575       TCP *:81 (LISTEN)
> nginx   18361 nobody    6u  IPv6 26577575       TCP *:81 (LISTEN)
> 
> If I use both:
> listen [::]:81;
> listen 81;
> 
> root at raptor> lsof -i :80
> COMMAND   PID   USER   FD   TYPE     DEVICE SIZE/OFF NODE NAME
> nginx   23184 nobody   10u  IPv6 0xd639be40    TCP *:81 (LISTEN)
> nginx   23184 nobody   11u  IPv4 0xd639b990    TCP *:81 (LISTEN)
> nginx   23235   root   10u  IPv6 0xd639be40       TCP *:81 (LISTEN)
> nginx   23235   root   11u  IPv4 0xd639b990       TCP *:81 (LISTEN)

This depends on kernel default ipv6only setting.
For example, in FreeBSD its default value is "net.inet6.ip6.v6only: 1"
In Linux it's off.

You may try to use
 listen [::]:81 ipv6only=on;
 listen 81;
to get consistent behaviour.

However, note that ipv6only value can be set only on nginx's start
before bind().


-- 
Igor Sysoev
http://sysoev.ru/en/