net/ipv4: convenience methods valid() and print()

Both methods are now available for Ipv4_address as well as for
Ipv4_address_prefix. An IPv4 address is invalid if it contains zeros only.
An IPv4 address prefix is invalid if its address is invalid and its
prefix is 32.

Ref #2139

repos/os/include/net/ipv4.h

@@ -22,10 +22,13 @@
 #include <util/endian.h>
 #include <net/netaddress.h>
 
+namespace Genode { class Output; }
+
 namespace Net
 {
 	enum { IPV4_ADDR_LEN = 4 };
-	typedef Network_address<IPV4_ADDR_LEN, '.', false> Ipv4_address;
+
+	class Ipv4_address;
 
 	class Ipv4_address_prefix;
 
@@ -33,6 +36,16 @@ namespace Net
 }
 
 
+struct Net::Ipv4_address : Network_address<IPV4_ADDR_LEN, '.', false>
+{
+	Ipv4_address(Genode::uint8_t value = 0) : Network_address(value) { }
+
+	Ipv4_address(void *src) : Network_address(src) { }
+
+	bool valid() const { return *this != Ipv4_address(); }
+};
+
+
 /**
  * Data layout of this class conforms to an IPv4 packet (RFC 791)
  *
@@ -200,7 +213,11 @@ class Net::Ipv4_packet
 struct Net::Ipv4_address_prefix
 {
 	Ipv4_address    address;
-	Genode::uint8_t prefix = 0;
+	Genode::uint8_t prefix = 32;
+
+	bool valid() const { return address.valid(); }
+
+	void print(Genode::Output &output) const;
 };
 
 

repos/os/src/lib/net/ipv4.cc

@@ -80,3 +80,9 @@ Genode::uint16_t Ipv4_packet::calculate_checksum(Ipv4_packet const &packet)
 
 const Ipv4_address Ipv4_packet::CURRENT((Genode::uint8_t)0x00);
 const Ipv4_address Ipv4_packet::BROADCAST((Genode::uint8_t)0xFF);
+
+
+void Ipv4_address_prefix::print(Genode::Output &output) const
+{
+	Genode::print(output, address, "/", prefix);
+}