dhcp ipv6

Soapm · 06-22-2013, 09:33 AM

I am curious what's causing this one ipv6 entry on my laptop? As you can see in netstat -tunlp, I have ipv6 pretty much disabled with the exception of this one entry. I don't think it's causing a problem, I was just curious what's causing it to be there. I know I can't disable dhclient since that would also stop it working for ipv4.

Code:

root@Peace:/# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      1997/rpcbind    
tcp        0      0 0.0.0.0:10000           0.0.0.0:*               LISTEN      3492/perl       
tcp        0      0 0.0.0.0:52210           0.0.0.0:*               LISTEN      4054/apache2    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      3467/sshd       
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      3325/cupsd      
tcp        0      0 0.0.0.0:23              0.0.0.0:*               LISTEN      2785/inetd      
tcp        0      0 0.0.0.0:44903           0.0.0.0:*               LISTEN      2028/rpc.statd  
udp        0      0 0.0.0.0:48177           0.0.0.0:*                           2028/rpc.statd  
udp        0      0 0.0.0.0:44337           0.0.0.0:*                           3328/dhclient   
udp        0      0 0.0.0.0:68              0.0.0.0:*                           3328/dhclient   
udp        0      0 0.0.0.0:111             0.0.0.0:*                           1997/rpcbind    
udp        0      0 0.0.0.0:631             0.0.0.0:*                           3325/cupsd      
udp        0      0 0.0.0.0:900             0.0.0.0:*                           1997/rpcbind    
udp        0      0 127.0.0.1:932           0.0.0.0:*                           2028/rpc.statd  
udp        0      0 0.0.0.0:58371           0.0.0.0:*                           3225/avahi-daemon: 
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           3225/avahi-daemon: 
udp        0      0 0.0.0.0:10000           0.0.0.0:*                           3492/perl       
udp        0      0 0.0.0.0:1900            0.0.0.0:*                           3589/minissdpd  
udp6       0      0 :::62879                :::*                                3328/dhclient

Normally I would expect this to be controlled by /etc/network/interfaces but I don't think I'm using that file on my laptop since this is how it looks;

Code:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

So if I'm not using /etc/network/interfaces, what other application can be causing DHCP to work? I don't recall configuring DHCP except during install.

Code:

root@Peace:/# lsb_release -a
LSB Version:	core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch
Distributor ID:	Debian
Description:	Debian GNU/Linux 7.1 (wheezy)
Release:	7.1
Codename:	wheezy

ifconfig

Code:

root@Peace:/# ifconfig
eth0      Link encap:Ethernet  HWaddr 30:f9:ed:ce:db:f1  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:41 Base address:0xe000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:20 errors:0 dropped:0 overruns:0 frame:0
          TX packets:20 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1240 (1.2 KiB)  TX bytes:1240 (1.2 KiB)

wlan0     Link encap:Ethernet  HWaddr a4:17:31:dd:c3:e5  
          inet addr:192.168.0.xxx  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2819604 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2518715 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:805667816 (768.3 MiB)  TX bytes:370129592 (352.9 MiB)

Ser Olmy · 06-22-2013, 04:56 PM

The list shows dhclient as listening on IPv6 socket ::/UDP/62879. As long as the kernel has IPv6 support, it may not be possible to prevent applications (especially if they're running as root) from binding to an IPv6 socket. Since none of your interfaces have IPv6 addresses this shouldn't be a problem, but it does seem a little odd.

Does the port number stay the same if you restart dhclient? This bug report seems to indicate that there is an NSUPDATE-related issure with dhclient, causing it to listen on random high ports.

Soapm · 06-22-2013, 08:54 PM

Quote:

Originally Posted by Ser Olmy

The list shows dhclient as listening on IPv6 socket ::/UDP/62879. As long as the kernel has IPv6 support, it may not be possible to prevent applications (especially if they're running as root) from binding to an IPv6 socket. Since none of your interfaces have IPv6 addresses this shouldn't be a problem, but it does seem a little odd.

Does the port number stay the same if you restart dhclient? This bug report seems to indicate that there is an NSUPDATE-related issure with dhclient, causing it to listen on random high ports.

I didn't think it was causing a problem but was curious why it didn't turn off with the rest of the ipv6 stuff. Makes sense what you said and I haven't seen it causing any problem. Yes, the port number changes at each restart and it does always appear to be a high port number (above 1024).

I guess that's the side effect of using a stock kernel but I never have luck with custom compiles, I invariably end up with a quirk and never have any idea how to answer the myriad of config questions so I end up defaulting everything which pretty much leaves me with what I started with...

Also, any idea how my DHCP is working without using the interface file??? I guess it was working out the box so I never questioned how until now.