wifi: Add delimiter signature check to AmpduSubframeHeader

src/wifi/model/ampdu-subframe-header.cc

@@ -44,7 +44,8 @@ AmpduSubframeHeader::GetInstanceTypeId (void) const
 
 AmpduSubframeHeader::AmpduSubframeHeader ()
   : m_length (0),
-    m_eof (0)
+    m_eof (0),
+    m_signature (0x4E) // Per 802.11 standard, the unique pattern is set to the value 0x4E.
 {
 }
 
@@ -63,7 +64,7 @@ AmpduSubframeHeader::Serialize (Buffer::Iterator i) const
 {
   i.WriteHtolsbU16 ((m_eof << 15) | m_length);
   i.WriteU8 (1); //not used, CRC always set to 1
-  i.WriteU8 (0x4E); // Per 802.11 standard, the unique pattern is set to the value 0x4E.
+  i.WriteU8 (m_signature);
 }
 
 uint32_t
@@ -74,14 +75,15 @@ AmpduSubframeHeader::Deserialize (Buffer::Iterator start)
   m_eof = (field & 0x8000) >> 15;
   m_length = (field & 0x3fff);
   i.ReadU8 (); //CRC
-  i.ReadU8 (); //SIG
+  m_signature = i.ReadU8 (); //SIG
   return i.GetDistanceFrom (start);
 }
 
 void
 AmpduSubframeHeader::Print (std::ostream &os) const
 {
-  os << "EOF = " << m_eof << ", length = " << m_length;
+  os << "EOF = " << m_eof << ", length = " << m_length
+     << ", signature = 0x" << std::hex << m_signature;
 }
 
 void
@@ -108,4 +110,10 @@ AmpduSubframeHeader::GetEof (void) const
   return m_eof;
 }
 
+bool
+AmpduSubframeHeader::IsSignatureValid (void) const
+{
+  return m_signature == 0x4E;
+}
+
 } //namespace ns3

src/wifi/model/ampdu-subframe-header.h

@@ -70,10 +70,19 @@ public:
    * \return the EOF field
    */
   bool GetEof (void) const;
+  /**
+   * Return whether the pattern stored in the delimiter
+   * signature field is correct, i.e. corresponds to the
+   * unique pattern 0x4E.
+   *
+   * \return true if the signature is valid, false otherwise
+   */
+  bool IsSignatureValid (void) const;
 
 private:
-  uint16_t m_length; //!< length field
-  bool m_eof;        //!< EOF field
+  uint16_t m_length;   //!< length field
+  bool m_eof;          //!< EOF field
+  uint8_t m_signature; //!< delimiter signature (should correspond to pattern 0x4E in order to be assumed valid)
 };
 
 } //namespace ns3