Re: [Patch] MdeModulePkg: Fix potential failure if UseDefaultAddress configured

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

Tested-by: Eugene Cohen <eugene@hp.com>

with the provision that Configure() retries are maintained for TCP cases

> -----Original Message-----
> From: Jiaxin Wu [mailto:jiaxin.wu@intel.com]
> Sent: Sunday, August 14, 2016 8:47 PM
> To: edk2-devel@lists.01.org
> Cc: Cohen, Eugene <eugene@hp.com>; Ye Ting <ting.ye@intel.com>;
> Fu Siyuan <siyuan.fu@intel.com>
> Subject: [Patch] MdeModulePkg: Fix potential failure if
> UseDefaultAddress configured
> 
> IpSb->Reconfig should not be set to TRUE to focal the reconfiguration
> during the policy changes from Static to DHCP. It's redundancy because
> the default router table and default addresses have been freed ahead
> (
> Detailed see Ip4Config2OnPolicyChanged() function). Otherwise, the
> potential failure will appear if UseDefaultAddress configured.
> Reproduce
> steps see below:
> 
> #1. Set policy to DHCP.
> #2. If DHCP process is not complete yet, then run one APP to invoke
> UDP4
> Configure with "UseDefaultAddress = TRUE" (loop to call UDP4
> Configure
> until Ip4Mode.IsConfigured changes to TRUE).
> #3. Even DHCP succeed but Ip4Mode.IsConfigured flag never set to
> TRUE
> 
> Concrete analysis is as follows:
> In #1, the policy will be set to DHCP, and then
> Ip4Config2OnPolicyChanged()
> will be called. In this function, if "IpSb->Reconfig" flag is set to TRUE,
> the original "IpSb->DefaultInterface" will be abandoned/freed once
> the
> DHCP process finished.
> 
> In #2, UDP4 Configure with "UseDefaultAddress = TRUE" is called, that
> means
> the default interface (IpSb->DefaultInterface) will be selected as
> current
> instance's interface.
> 
> In #3, when DHCP process finished, the original DefaultInterface will be
> abandoned/freed because "IpSb->Reconfig" flag is true. Meanwhile,
> one new
> interface is assigned to "IpSb->DefaultInterface". This new interface is
> different to the original one assigned to the UDP4 Configured instance.
> So,
> even DHCP process succeed, the up caller will never have the chance
> to get
> it's truly status.
> 
> Cc: Cohen Eugene <eugene@hp.com>
> Cc: Ye Ting <ting.ye@intel.com>
> Cc: Fu Siyuan <siyuan.fu@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
> ---
>  MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git
> a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
> b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
> index f91a935..75ad301 100644
> --- a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
> +++ b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
> @@ -148,11 +148,10 @@ Ip4Config2OnPolicyChanged (
> 
>    //
>    // Start the dhcp configuration.
>    //
>    if (NewPolicy == Ip4Config2PolicyDhcp) {
> -    IpSb->Reconfig = TRUE;
>      Ip4StartAutoConfig (&IpSb->Ip4Config2Instance);
>    }
> 
>  }
> 
> --
> 1.9.5.msysgit.1