network: add a function to detect IPv4 APIPA addresses

Author: TommyPec

CHANGES.md

@@ -16,6 +16,8 @@ This file is a best-effort approach to solving this issue; we will do our best b
 
 ### New API
 
+* (network) Added a function to detect IPv4 APIPA addresses (169.254.0.0/16).
+
 ### Changes to existing API
 
 * (internet-apps) Added a parameter to the RADVD helper to announce a prefix without the autoconfiguration flag.

src/network/utils/ipv4-address.cc

@@ -281,6 +281,14 @@ Ipv4Address::IsLocalMulticast() const
     return (m_address & 0xffffff00) == 0xe0000000;
 }
 
+bool
+Ipv4Address::IsLinkLocal() const
+{
+    NS_LOG_FUNCTION(this);
+    // Link-Local address is 169.254.0.0/16
+    return (m_address & 0xffff0000) == 0xa9fe0000;
+}
+
 void
 Ipv4Address::Serialize(uint8_t buf[4]) const
 {

src/network/utils/ipv4-address.h

@@ -112,6 +112,14 @@ class Ipv4Address
      * @return true only if address is in local multicast address scope, 224.0.0.0/24
      */
     bool IsLocalMulticast() const;
+    /**
+     * @brief If the IPv4 address is an APIPA address (169.254/16).
+     *
+     * The Automatic Private IP Address is described in \RFC{3927}
+     *
+     * @return true if the address is link-local, false otherwise
+     */
+    bool IsLinkLocal() const;
     /**
      * @brief Combine this address with a network mask
      *