dhcpcd-discuss

On 2016-01-31 15:03, Nick Williams wrote:
> > On Jan 31, 2016, at 7:48 AM, Roy Marples <roy@xxxxxxxxxxxx> wrote:
> >
> > Or you can look at the file dhcpcd-definitions.conf in the dhcpcd 
> > source tree to find the full definitions and decoding for every RFC 
> > DHCP option I know of, along with a short description and RFC number.
>
> Excellent! That file was VERY helpful. Using that, I was able to
> figure the following out (if I’m screwing something up, let me know):
>
> We currently send the following options (some of them all the time,
> some of them just sometimes) with DHCLIENT with DHCPv4:
>
> request subnet-mask
> request broadcast-address
> requset routers
> request domain-name-servers
> request domain-name
> request interface-mtu
>
> And I BELIEVE those are equivalent to the following DHCPCD options:
>
> option subnet_mask
> option broadcast_address
> option routers
> option domain_name_servers
> option domain_search
> option interface_mtu

Wrong
domain_search is a different option from domain_name.
Normally best to request both options.

> Also, we currently send the following DHCPv6 options with DHCLIENT:
>
> request domain-name-servers
> request domain-name
>
> And I BELIEVE those are equivalent to the following DHCPCD options:
>
> dhcp6_option name_servers
> dhcp6_option domain_search

Correct.
However, if you specify ANY dhcp6_ option then you need to specify ALL 
dhcp6_ options you want, otherwise dhcpcd will request matching dhcp6_ 
option from the dhcp4 counterparts.

> I didn’t find dhcp6_options for subnet mask, broadcast address, or
> routers, but I’m guessing that’s because those aren’t DHCPv6 options,
> and it’s all automatic, because I don’t see those in
> dhclient/WIDE/Google, and we aren’t sending them currently with
> dhclient.

:)
In IPv6, there is no subnet mask. There is a prefix length. In IPv4 this 
is called CIDR and ranges from 0-32 to match the subnet mask.
Also a generic broadcast address doesn't exist in IPv6 - broadcast 
addresses are normally special network addresses such as ALL DHCP 
Servers

> The dhcpcd.conf man page says that the DHCPv6 equivalent of “option”
> is “dhcp6_option,” but it doesn’t say what the DHCPv6 equivalent of
> “nooption” is. Is that also just “dhcp6_nooption?”

Yes

> Finally, we support IPv6 information-only/parameters-only
> configuration (where only stateless configuration parameters are
> requested). This is dhclient command-line option “-S” and WIDE client
> configuration option “information-only.” By name, I couldn’t find any
> equivalent option in the man pages or in dhcpcd-definitions.conf, and
> Googling around for about an hour didn’t turn up which DHCPv6 option
> dhclient/WIDE send when information-only mode is enabled. Does DHCPCD
> have an equivalent for this? Does specifying the stateless
> configuration option “ipv6ra_autoconf" do the equivalent?

from dhcpcd(8)
     --inform6
             Performs a DHCPv6 Information Request.  No address is 
requested
             or specified, but all other DHCPv6 options are allowed.  
This is
             normally performed automatically when the IPv6 Router 
Advertises
             that the client should perform this operation.  This option 
is
             only needed when dhcpcd is not processing IPv6RA messages 
and the
             need for DHCPv6 Information Request exists.

Roy