Re: [Patch] MdeModulePkg: Update IP4 stack to support point-to-point link with 31-bit mask.

["Wu, Jiaxin" <jiaxin.wu@intel.com>]

Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>



> -----Original Message-----
> From: Fu, Siyuan
> Sent: Wednesday, October 18, 2017 1:17 PM
> To: edk2-devel@lists.01.org
> Cc: Wu, Jiaxin <jiaxin.wu@intel.com>; Ye, Ting <ting.ye@intel.com>
> Subject: [Patch] MdeModulePkg: Update IP4 stack to support point-to-point
> link with 31-bit mask.
> 
> This patch is to follow RFC3021 which allows to use 31-bit mask
> in point-to-point link.
> If a 31-bit subnet mask is assigned to a point-to-point link, it
> leaves the <Host-number> with only 1 bit.  Consequently, only two
> possible addresses may result:
>   {<Network-number>, 0} and {<Network-number>, -1}
> These addresses have historically been associated with network and
> broadcast addresses (see Section 2.2).  In a point-to-point link with
> a 31-bit subnet mask, the two addresses above MUST be interpreted as
> host addresses.
> 
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
> Cc: Wu Jiaxin <jiaxin.wu@intel.com>
> Cc: Ye Ting <ting.ye@intel.com>
> ---
>  MdeModulePkg/Include/Library/NetLib.h             |  6 ++++--
>  MdeModulePkg/Library/DxeNetLib/DxeNetLib.c        | 14 ++++++++++----
>  MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c | 20
> +++++++++++++-------
>  3 files changed, 27 insertions(+), 13 deletions(-)
> 
> diff --git a/MdeModulePkg/Include/Library/NetLib.h
> b/MdeModulePkg/Include/Library/NetLib.h
> index 4cd4227..b9df46c 100644
> --- a/MdeModulePkg/Include/Library/NetLib.h
> +++ b/MdeModulePkg/Include/Library/NetLib.h
> @@ -414,8 +414,10 @@ NetGetIpClass (
> 
>    ASSERT if NetMask is zero.
> 
> -  If all bits of the host address of IP are 0 or 1, IP is also not a valid unicast
> address.
> -
> +  If all bits of the host address of IP are 0 or 1, IP is also not a valid unicast
> address,
> +  except when the originator is one of the endpoints of a point-to-point link
> with a 31-bit
> +  mask (RFC3021).
> +
>    @param[in]  Ip                    The IP to check against.
>    @param[in]  NetMask               The mask of the IP.
> 
> diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> index 1ee77fe..b8544b8 100644
> --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
> @@ -637,7 +637,9 @@ NetGetIpClass (
> 
>    ASSERT if NetMask is zero.
> 
> -  If all bits of the host address of IP are 0 or 1, IP is also not a valid unicast
> address.
> +  If all bits of the host address of IP are 0 or 1, IP is also not a valid unicast
> address,
> +  except when the originator is one of the endpoints of a point-to-point link
> with a 31-bit
> +  mask (RFC3021).
> 
>    @param[in]  Ip                    The IP to check against.
>    @param[in]  NetMask               The mask of the IP.
> @@ -657,9 +659,13 @@ NetIp4IsUnicast (
>    if (Ip == 0 || IP4_IS_LOCAL_BROADCAST (Ip)) {
>      return FALSE;
>    }
> -
> -  if (((Ip &~NetMask) == ~NetMask) || ((Ip &~NetMask) == 0)) {
> -    return FALSE;
> +
> +  if (NetGetMaskLength (NetMask) != 31) {
> +    if (((Ip &~NetMask) == ~NetMask) || ((Ip &~NetMask) == 0)) {
> +      return FALSE;
> +    }
> +  } else {
> +    return TRUE;
>    }
> 
>    return TRUE;
> diff --git a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
> b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
> index 7c7d182..b8160c1 100644
> --- a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
> +++ b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
> @@ -314,16 +314,22 @@ Ip4StationAddressValid (
> 
>    //
>    // Station address can't be subnet broadcast/net broadcast address
> +  // RFC3021: In a point-to-point network with 31-bit mask, the <Host-
> number> only has
> +  // 1 bit, only two possible addresses may result:
> +  //   {<Network-number>, 0} and {<Network-number>, -1}
> +  // The two address above must be interpreted as host addresses.
>    //
> -  if ((Ip == (Ip & Netmask)) || (Ip == (Ip | ~Netmask))) {
> -    return FALSE;
> -  }
> +  if (Len != 31) {
> +    if ((Ip == (Ip & Netmask)) || (Ip == (Ip | ~Netmask))) {
> +      return FALSE;
> +    }
> 
> -  NetBrdcastMask = gIp4AllMasks[MIN (Len, Type << 3)];
> +    NetBrdcastMask = gIp4AllMasks[MIN (Len, Type << 3)];
> 
> -  if (Ip == (Ip | ~NetBrdcastMask)) {
> -    return FALSE;
> +    if (Ip == (Ip | ~NetBrdcastMask)) {
> +      return FALSE;
> +    }
>    }
> 
>    return TRUE;
> -}
> \ No newline at end of file
> +}
> --
> 1.9.5.msysgit.1