Re: Breaking change issue with NetworkPkg/Ip6Dxe/Ip6ConfigImlp.[c, h]

["Cohen, Eugene" <eugene@hp.com>]

We've been hit by this same kind of issue and it's really painful, especially as it affects shipping systems.

Long term I think we need an extensible/revisioned data format so we can get forwards and backwards compatibility between NVRAM data and FW.

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Larry Cleeton
> Sent: Friday, August 05, 2016 9:35 AM
> To: Ye, Ting <ting.ye@intel.com>; edk2-devel@lists.01.org
> Subject: Re: [edk2] Breaking change issue with
> NetworkPkg/Ip6Dxe/Ip6ConfigImlp.[c, h]
> 
> I agree with your assessment about leaving the data structure as it is.   I just
> wanted to highlight it as it may impact others.
> 
> The bottom line is my development group is entirely responsible for vetting
> any changes coming from the EDK2 into our product.  This one slipped by us.
> 
> --Larry
> 
> -----Original Message-----
> From: Ye, Ting [mailto:ting.ye@intel.com]
> Sent: Thursday, August 4, 2016 8:25 PM
> To: Larry Cleeton <Larry.Cleeton@microsoft.com>; edk2-devel@lists.01.org
> Subject: RE: Breaking change issue with
> NetworkPkg/Ip6Dxe/Ip6ConfigImlp.[c, h]
> 
> Hi Larry,
> 
> We are very sorry about the impact you suffered today. We made the
> change in early 2013 to support the existing NVRAM variable when firmware
> image was updated from IA32 to X64. Unfortunately we introduced an
> incompatibility issue as you raised. Now we prefer to keep the existing
> definition, since if we change it back that would introduce another similar
> incompatibility issue. What do you think about this?
> 
> Best Regards,
> Ye Ting
> 
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Larry Cleeton
> Sent: Wednesday, August 03, 2016 4:55 AM
> To: edk2-devel@lists.01.org
> Subject: [edk2] Breaking change issue with
> NetworkPkg/Ip6Dxe/Ip6ConfigImlp.[c, h]
> 
> This commit (fdc4b0b147b386e966e99893526181dfae9eaeef) changed a data
> structure that is stored in an NVRAM variable.
> See NetworkPkg/Ip6Dxe/Ip6ConfigImpl.[c,h]
> 
> This data structure:
> 
> typedef struct {
>   UINT16                    Offset;
>   UINTN                     DataSize;
>   EFI_IP6_CONFIG_DATA_TYPE  DataType;
> } IP6_CONFIG_DATA_RECORD;
> 
> Is now:
> 
> typedef struct {
>   UINT16                    Offset;
>   UINT32                     DataSize;    <---------------- changed size in 64bit
> environments
>   EFI_IP6_CONFIG_DATA_TYPE  DataType;
> } IP6_CONFIG_DATA_RECORD;
> 
> Unfortunately with a 64bit implementation this current structure is now
> *not* compatible with an existing NVRAM variable written with the previous
> version of the structure. It's causing me considerable grief so I'm just sharing
> the discovery.  It would only impact you if you update some 64bit machine's
> firmware with a new version containing this change.
> 
> --Larry
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