Kernel: Implement is_zero for RoutingDecision

Author: https://github.com/deoxxa
Commit: https://github.com/SerenityOS/serenity/commit/b15a7c435ff
Pull-request: https://github.com/SerenityOS/serenity/pull/499
Reviewed-by: https://github.com/awesomekling

Kernel/Net/IPv4Socket.cpp

@@ -170,7 +170,7 @@ ssize_t IPv4Socket::sendto(FileDescription&, const void* data, size_t data_lengt
     }
 
     auto routing_decision = route_to(m_peer_address, m_local_address);
-    if (!routing_decision.adapter || routing_decision.next_hop.is_zero())
+    if (routing_decision.is_zero())
         return -EHOSTUNREACH;
 
     if (m_local_address.to_u32() == 0)

Kernel/Net/Routing.cpp

@@ -11,6 +11,11 @@ Lockable<HashMap<IPv4Address, MACAddress>>& arp_table()
     return *the;
 }
 
+bool RoutingDecision::is_zero() const
+{
+    return adapter.is_null() || next_hop.is_zero();
+}
+
 RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source)
 {
     auto target_addr = target.to_u32();

Kernel/Net/Routing.h

@@ -6,6 +6,8 @@ struct RoutingDecision
 {
     WeakPtr<NetworkAdapter> adapter;
     MACAddress next_hop;
+
+    bool is_zero() const;
 };
 
 RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source);

Kernel/Net/TCPSocket.cpp

@@ -126,7 +126,7 @@ int TCPSocket::protocol_send(const void* data, int data_length)
 void TCPSocket::send_tcp_packet(u16 flags, const void* payload, int payload_size)
 {
     auto routing_decision = route_to(peer_address(), local_address());
-    ASSERT(!!routing_decision.adapter);
+    ASSERT(!routing_decision.is_zero());
 
     auto buffer = ByteBuffer::create_zeroed(sizeof(TCPPacket) + payload_size);
     auto& tcp_packet = *(TCPPacket*)(buffer.pointer());
@@ -242,7 +242,7 @@ KResult TCPSocket::protocol_listen()
 KResult TCPSocket::protocol_connect(FileDescription& description, ShouldBlock should_block)
 {
     auto routing_decision = route_to(peer_address(), local_address());
-    if (!routing_decision.adapter || routing_decision.next_hop.is_zero())
+    if (routing_decision.is_zero())
         return KResult(-EHOSTUNREACH);
     if (!has_specific_local_address())
         set_local_address(routing_decision.adapter->ipv4_address());

Kernel/Net/UDPSocket.cpp

@@ -64,7 +64,7 @@ int UDPSocket::protocol_receive(const KBuffer& packet_buffer, void* buffer, size
 int UDPSocket::protocol_send(const void* data, int data_length)
 {
     auto routing_decision = route_to(peer_address(), local_address());
-    if (!routing_decision.adapter)
+    if (routing_decision.is_zero())
         return -EHOSTUNREACH;
     auto buffer = ByteBuffer::create_zeroed(sizeof(UDPPacket) + data_length);
     auto& udp_packet = *(UDPPacket*)(buffer.pointer());