MdeModulePkg: Update IP4 stack to support point-to-point link with 31-bit mask.

V2 update: Directly use NetIp4IsUnicast() to check station address in IP driver.

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

3 files changed, 18 insertions, 27 deletions

diff --git a/MdeModulePkg/Include/Library/NetLib.h b/MdeModulePkg/Include/Library/NetLib.h
index 4cd42270f6..b9df46c50f 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 1ee77fe036..b8544b89ab 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 7c7d182073..b582ccf13f 100644
--- a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
+++ b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Common.c
@@ -287,10 +287,6 @@ Ip4StationAddressValid (
   IN IP4_ADDR               Netmask

   )

 {

-  IP4_ADDR                  NetBrdcastMask;

-  INTN                      Len;

-  INTN                      Type;

-

   //

   // Only support the station address with 0.0.0.0/0 to enable DHCP client.

   //

@@ -301,29 +297,16 @@ Ip4StationAddressValid (
   //

   // Only support the continuous net masks

   //

-  if ((Len = NetGetMaskLength (Netmask)) == (IP4_MASK_MAX + 1)) {

+  if (NetGetMaskLength (Netmask) == (IP4_MASK_MAX + 1)) {

     return FALSE;

   }

 

   //

   // Station address can't be class D or class E address

   //

-  if ((Type = NetGetIpClass (Ip)) > IP4_ADDR_CLASSC) {

-    return FALSE;

-  }

-

-  //

-  // Station address can't be subnet broadcast/net broadcast address

-  //

-  if ((Ip == (Ip & Netmask)) || (Ip == (Ip | ~Netmask))) {

+  if (NetGetIpClass (Ip) > IP4_ADDR_CLASSC) {

     return FALSE;

   }

 

-  NetBrdcastMask = gIp4AllMasks[MIN (Len, Type << 3)];

-

-  if (Ip == (Ip | ~NetBrdcastMask)) {

-    return FALSE;

-  }

-

-  return TRUE;

-}
\ No newline at end of file
+  return NetIp4IsUnicast (Ip, Netmask);

+}