dhcpcd-discuss

Hi Roy,

I have upgraded dhcp client to dhcpcd-7.0.0-rc1. I am using default dhcpcd.conf file
According to my current network configuration M bit is disabled and O bit is set.

Please check below the Router advertisement packet:
--------------------------------------------------------------------------XX-----------------------------------------------------------------------
Internet Control Message Protocol v6
    Type: Router Advertisement (134)
    Code: 0
    Checksum: 0x93b0 [correct]
    [Checksum Status: Good]
    Cur hop limit: 64
    Flags: 0x40
        0... .... = Managed address configuration: Not set
        .1.. .... = Other configuration: Set
        ..0. .... = Home Agent: Not set
        ...0 0... = Prf (Default Router Preference): Medium (0)
        .... .0.. = Proxy: Not set
        .... ..0. = Reserved: 0
    Router lifetime (s): 1800
    Reachable time (ms): 0
    Retrans timer (ms): 0
    ICMPv6 Option (Source link-layer address : 30:8d:99:33:70:00)
    ICMPv6 Option (Prefix information : 2017::/64)
--------------------------------------------------------------------XX------------------------------------------------------------
Dhcpcd replies with following solicit message:
-----------------------------------------------------------XX------------------------------------------------------------------------
DHCPv6
    Message type: Solicit (1)
    Transaction ID: 0x83a3ef
    Client Identifier
    Elapsed time
    Vendor Class
    Identity Association for Non-temporary Address
        Option: Identity Association for Non-temporary Address (3)
        Length: 12
        Value: b9a707ff0000000000000000
        IAID: b9a707ff
        T1: 0
        T2: 0
    Identity Association for Prefix Delegation
    Fully Qualified Domain Name
    Reconfigure Accept
    Option Request
------------------------------------------------------XX----------------------------------------------------------------------
This implies dhcpcd client do not omits " IANA" field and hence I am getting IPv6 address from dhcpv6 server.
Do you think this could be due to older linux kernel version. Could you suggest if any linux patch might resolve this issue.

Can you suggest some configuration or sample dhcpcd.conf file which can support stateless dhcp configuration.

Regards
Renu

-----Original Message-----
From: Roy Marples [mailto:roy@xxxxxxxxxxxx] 
Sent: Thursday, June 22, 2017 2:04 PM
To: Renu Bansal; dhcpcd-discuss@xxxxxxxxxxxx
Cc: Swarnpal Singh; Saurabh Pandey
Subject: Re: [dhcpcd-discuss] dhcpcd6.11.0 Stateless dhcp support

Hi Renu

On 19/06/2017 11:27, Renu Bansal wrote:
> I am getting an issue while configuring  my device with stateless 
> DHCPv6 server. I need to receive SLAAC address from RA and other 
> configuration from DHCPv6 Server
> 
> Following is my setup's configuration:
> 
> Server:
> 
> *         Windows Server 2012 R2
> 
> Client:
> 
> *         dhcpcd v6.11.0, and
> 
> *         linux kernel: v2.6.32
> 
>  
> 
> Currently  Network Router is configured to send RA packets with 
> following bit configurations:
> 
> M-bit: 0
> 
> O-bit: 1
> 
>  
> 
> Currently we are getting both IPv6 address assigned by DHCPv6 server 
> as well as one from SLAAC. but i think as per M Bit Configuration, 
> DHCPv6 address should have been ignored.

O and M are just hints about what the default DHCPv6 client should do.
You can override this in dhcpcd.conf

> Could you please suggest parameters to be added in conf file for 
> configuring dhcpcd6.11.0 to use SLAAC. Also, please tell me if this 
> behaviour could be due to some missing configuration of older linux 
> kernel version.

The stock dhcpcd.conf should work fine
Saying that, 6.11.0 is old and you should upgrade to 6.11.5, or ideally try dhcpcd-7.0.0-rc1 if here are still problems for you.
Your kernel is still quite old, 2.6 is positively ancient!
dhcpcd should still set SLAAC correctly though.
Be warned that dhcpcd does try to support newer IPv6 setups in Linux and I've not tested with an old kernel for a very long time.

> To avoid IPv6 configuration from DHCPv6, there can be two possible ways:
> 
> 1. DHCP request omits 'IANA' field, so as not to get back the address.

Yes.
dhcpcd will do this on stock config if the O bit is set.

> 2. Address is received from DHCPv6 but is ignored by the dhcpd client.
> 
> (Could you let me know which of the above would be the case for 
> Stateless DHCP)

I'm not sure dhcpcd supports this.
If there is an address in the reply, dhcpcd will try to use it.
But the server won't make up an IAID ... so if dhcpcd didn't request an address the server shouldn't set one.

Roy