dhcpcd-discuss

On 3 December 2017 22:22:58 Roy Marples <roy@xxxxxxxxxxxx> wrote:

> Hi Roger
>
> On 03/12/2017 17:52, roger wrote:
> > I am struggling to configure a monitoring only interface using dhcpcd. I
> > need to the interface not to have any addresses configured on it. ipv4
> > is easy but I cannot find a way to stop ipv6 addresses being configured.
> >
> > This is what I have tried so far.
> >
> > interface enx00e04c68a9f3
> > noipv4
> > noipv6
> > noipv6rs
> > ipv6ra_noautoconf
>
> noipv4 and noipv6 by themselves are sufficient
>
> > This results in.
> >
> > enx00e04c68a9f3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
> >          inet6 2001:8b0:1418:4c2f:2e0:4cff:fe68:a9f3  prefixlen 64
> > scopeid 0x0<global>
> >          inet6 fe80::2e0:4cff:fe68:a9f3  prefixlen 64  scopeid 0x20<link>
> >          inet6 fda0:4d7f:afbb:0:2e0:4cff:fe68:a9f3  prefixlen 64 scopeid
> > 0x0<global>
> >          ether 00:e0:4c:68:a9:f3  txqueuelen 1000  (Ethernet)
> >          RX packets 2228  bytes 238745 (233.1 KiB)
> >          RX errors 0  dropped 4  overruns 0  frame 0
> >          TX packets 32  bytes 4942 (4.8 KiB)
> >          TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
> >
> > Has anyone got any suggestions on how I can get rid of those ipv6
> > addresses.
>
> What makes you think dhcpcd is assigning them?
> Did you disable the kernel handling RA as well?
>
> Roy

Hi Roy,

Thank you for the quick response. I was hoping the noipv6 option would do 
the kernel parameters stuff for me. It would seem reasonable that telling 
dhcpcd that I do not want ipv6 on an interface should be interpreted that 
all the necessary actions to fully disable it should be taken, including 
setting kernel parameters.

I had not read the man page closely enough.

" noipv6  Don't attmept to configure an IPv6 address." sic.

I was interpreting noipv6 as "disable ipv6 on this interface completely". I 
still think it is confusing that if you tell dhcpcd that you do not want 
ipv6 addresses, that you still end up with ones configured by the kernel.

Because this interface is a monitor I still want the link level to be 
active, I have had problems in the past with pcap not working when ipv6 was 
disabled at the kernel level. I think I will try it first with just 
accept_ra turned off.

Ah well. sysctl here I come.

Roger