IPv4: Implement bind() for TCP and UDP sockets.

We can't accept connections just yet, but this patch makes it possible to
bind() to a given source address/port.

Kernel/Net/IPv4Socket.cpp

@@ -11,6 +11,7 @@
 #include <Kernel/Net/ARP.h>
 #include <Kernel/Net/Routing.h>
 #include <LibC/errno_numbers.h>
+#include <Kernel/FileSystem/FileDescriptor.h>
 
 #define IPV4_SOCKET_DEBUG
 
@@ -63,7 +64,13 @@ KResult IPv4Socket::bind(const sockaddr* address, socklen_t address_size)
     if (address->sa_family != AF_INET)
         return KResult(-EINVAL);
 
-    ASSERT_NOT_REACHED();
+    auto& ia = *(const sockaddr_in*)address;
+    m_source_address = IPv4Address((const byte*)&ia.sin_addr.s_addr);
+    m_source_port = ntohs(ia.sin_port);
+
+    dbgprintf("IPv4Socket::bind %s{%p} to port %u\n", class_name(), this, m_source_port);
+
+    return protocol_bind();
 }
 
 KResult IPv4Socket::connect(FileDescriptor& descriptor, const sockaddr* address, socklen_t address_size, ShouldBlock should_block)
@@ -91,8 +98,10 @@ void IPv4Socket::detach(FileDescriptor&)
     --m_attached_fds;
 }
 
-bool IPv4Socket::can_read(FileDescriptor&) const
+bool IPv4Socket::can_read(FileDescriptor& descriptor) const
 {
+    if (descriptor.socket_role() == SocketRole::Listener)
+        return can_accept();
     if (protocol_is_disconnected())
         return true;
     return m_can_read;

Kernel/Net/IPv4Socket.h

@@ -48,6 +48,7 @@ protected:
 
     int allocate_source_port_if_needed();
 
+    virtual KResult protocol_bind() { return KSuccess; }
     virtual int protocol_receive(const ByteBuffer&, void*, size_t, int, sockaddr*, socklen_t*) { return -ENOTIMPL; }
     virtual int protocol_send(const void*, int) { return -ENOTIMPL; }
     virtual KResult protocol_connect(FileDescriptor&, ShouldBlock) { return KSuccess; }
@@ -59,6 +60,8 @@ private:
 
     bool m_bound { false };
     int m_attached_fds { 0 };
+
+    IPv4Address m_source_address;
     IPv4Address m_destination_address;
 
     DoubleBuffer m_for_client;

Kernel/Net/TCPSocket.cpp

@@ -203,3 +203,12 @@ bool TCPSocket::protocol_is_disconnected() const
 {
     return m_state == State::Disconnecting || m_state == State::Disconnected;
 }
+
+KResult TCPSocket::protocol_bind()
+{
+    LOCKER(sockets_by_port().lock());
+    if (sockets_by_port().resource().contains(source_port()))
+        return KResult(-EADDRINUSE);
+    sockets_by_port().resource().set(source_port(), this);
+    return KSuccess;
+}

Kernel/Net/TCPSocket.h

@@ -38,6 +38,7 @@ private:
     virtual KResult protocol_connect(FileDescriptor&, ShouldBlock) override;
     virtual int protocol_allocate_source_port() override;
     virtual bool protocol_is_disconnected() const override;
+    virtual KResult protocol_bind() override;
 
     dword m_sequence_number { 0 };
     dword m_ack_number { 0 };

Kernel/Net/UDPSocket.cpp

@@ -104,3 +104,12 @@ int UDPSocket::protocol_allocate_source_port()
     }
     return -EADDRINUSE;
 }
+
+KResult UDPSocket::protocol_bind()
+{
+    LOCKER(sockets_by_port().lock());
+    if (sockets_by_port().resource().contains(source_port()))
+        return KResult(-EADDRINUSE);
+    sockets_by_port().resource().set(source_port(), this);
+    return KSuccess;
+}

Kernel/Net/UDPSocket.h

@@ -20,6 +20,7 @@ private:
     virtual int protocol_send(const void*, int) override;
     virtual KResult protocol_connect(FileDescriptor&, ShouldBlock) override { return KSuccess; }
     virtual int protocol_allocate_source_port() override;
+    virtual KResult protocol_bind() override;
 };
 
 class UDPSocketHandle : public SocketHandle {