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

[Andrei Borzenkov]

21.11.2016 16:09, Daniel Kiper пишет:
> 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...
> 

Yes. Sorry, it was probably my fault to refer to DHCP in the first place.

>> +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.
> 

Well, net_default_server is not really tied to any BOOTP/DHCP at all,
although it may be initially set based on content of ACK packet. I was
confused by dhcp_server_name, but they it is unrelated to next server.

I'd rather used net_<interface>_next_server for clarity, both "server"
and "server_ip" are indeed too vague in this case.

> Otherwise LGTM.
> 
> Daniel
>