Introduce ipAvailable network function

include/tools.h

@@ -231,6 +231,15 @@ IpAddress getBestPublicIps(IpMode mode);
  */
 std::string getBestPublicIp();
 
+/** Checks if IP address is available
+ *
+ * Check if the given IP address is configured on any network interface of the system
+ *
+ * @param addr the IP address to check.
+ * @return true if the IP address is available on the system.
+ */
+bool ipAvailable(const IpAddress& addr);
+
 /** Converts file size to human readable format.
  *
  * This function will convert a number to its equivalent size using units.

src/server/internalServer.cpp

@@ -476,6 +476,11 @@ bool InternalServer::start() {
       std::cerr << "IP address " << address << " is not a valid IP address" << std::endl;
       return false;
     }
+
+    if (!ipAvailable(m_addr)) {
+      std::cerr << "IP address " << (m_addr.addr.empty() ? m_addr.addr6 : m_addr.addr) << " is not available on this system" << std::endl;
+      return false;
+    }
   }
 
   if (m_ipMode == IpMode::all) {

src/tools/networkTools.cpp

@@ -243,4 +243,16 @@ std::string getBestPublicIp()
   return getBestPublicIps(IpMode::ipv4).addr;
 }
 
+bool ipAvailable(const IpAddress& addr) 
+{
+  auto interfaces = kiwix::getNetworkInterfacesIPv4Or6();
+  for (const auto& interface : interfaces) {
+    IpAddress interfaceIps = interface.second;
+    if (!interfaceIps.empty4() && interfaceIps.addr == addr.addr) return true;
+    if (!interfaceIps.empty6() && interfaceIps.addr6 == addr.addr6) return true;
+  }
+
+  return false;
+}
+
 } // namespace kiwix