Re: [2.02][PATCH] bootp: export server IP as environment variable

[Daniel Kiper]

On Fri, Nov 18, 2016 at 09:11:47PM +0300, Andrei Borzenkov wrote:
> 17.11.2016 22:02, Daniel Kiper ??????????:
> > On Fri, Mar 18, 2016 at 08:42:00PM +0300, Andrei Borzenkov wrote:
> >> Network boot autoconfiguration sets default server to next server IP
> >> (siaddr) from BOOTP/DHCP reply, but manual configuration using net_bootp
> >> exports only server name. Unfortunately semantic of server name is not
> >> clearly defined. BOOTP RFC 951 defines it only for client request, and
> >> DHCP RFC 1541 only mentions it, without any implied usage. It looks like
> >> this field is mostly empty in server replies.
> >>
> >> Export next server IP as net_<interface>_server_ip variable. This allows
> >> grub configuration script to set $root/$prefix based on information 
> >> obtained
> >> by net_bootp.
> >>
> >> Reported and tested by: Nikunj A Dadhania <address@hidden>
> >> Cc: address@hidden
> >>
> >> ---
> >>
> >> @Nikunj: cosmetic changes comparing with version you tested - no need to
> >> allocate small buffer dynamically.
> >>
> >> @Vladimir: I think this is useful; I will update networking documentation
> >> in followup patch.
> >
> > Vladimir, Andrei, could you take care of it?
> >
> > Daniel
> >
>
> I added documentation (not worth separate patch); if there are no
> objections I commit.
>
>
> From: Andrei Borzenkov <address@hidden>
> Subject: [2.02][PATCH] bootp: export server IP as environment variable
>
> Network boot autoconfiguration sets default server to next server IP
> (siaddr) from BOOTP/DHCP reply, but manual configuration using net_bootp
> exports only server name. Unfortunately semantic of server name is not
> clearly defined. BOOTP RFC 951 defines it only for client request, and
> DHCP RFC 1541 only mentions it, without any implied usage. It looks like
> this field is mostly empty in server replies.
>
> Export next server IP as net_<interface>_server_ip variable. This allows
> grub configuration script to set $root/$prefix based on information obtained
> by net_bootp.
>
> Reported and tested by: Nikunj A Dadhania <address@hidden>
> Cc: address@hidden
>
> ---
>  docs/grub.texi        | 11 +++++++++++
>  grub-core/net/bootp.c | 24 ++++++++++++++----------
>  2 files changed, 25 insertions(+), 10 deletions(-)
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index 82f6fa4..bb03875 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -2446,6 +2446,10 @@ The boot file name provided by DHCP.  Read-only.
>  The name of the DHCP server responsible for these boot parameters.
>  Read-only.
>
> address@hidden address@hidden<interface>}_server_ip
> +The IP address of the next (usually, TFTP) server provided by DHCP.

BOOTP instead of DHCP? However, then we should change DHCP everywhere too...

> +Read-only.
> +
>  @item net_default_interface
>  Initially set to name of network interface that was used to load grub.
>  Read-write, although setting it affects only interpretation of
> @@ -3062,6 +3066,7 @@ These variables have special meaning to GRUB.
>  * address@hidden<interface>}_hostname::
>  * address@hidden<interface>}_ip::
>  * address@hidden<interface>}_mac::
> +* address@hidden<interface>}_server_ip::

There is something known as net_default_server which contains next IP address.
Should not we be more consistent and use "address@hidden<interface>}_server" 
instead
of "address@hidden<interface>}_server_ip" here and there.

Otherwise LGTM.

Daniel