dhcp: Add RFC 2131 - DHCP Inform

This addresses the issue: #14

Ref: http://www.freesoft.org/CIE/RFC/2131/27.htm

Signed-off-by: Simarpreet Singh <[email protected]>

Author: simar7

Diff for: dhcp.go

@@ -103,6 +103,10 @@ func (h *dhcpServerHandler) ServeDHCP(p dhcp.Packet, msgType dhcp.MessageType, o
 				break
 			}
 		}
+
+	case dhcp.Inform:
+		//nic := p.CHAddr().String()
+		return dhcp.ReplyPacket(p, dhcp.ACK, h.ip, nil, 0, nil)
 	}
 	return nil
 }

Diff for: dhcp_test.go

@@ -91,3 +91,15 @@ func TestServeDHCPRelease_OK(t *testing.T) {
 
 	assert.Equal(t, expected, actual)
 }
+
+func TestServeDHCPInform_OK(t *testing.T) {
+	dhcpServer := newDHCPServer()
+	p := dhcp.NewPacket(dhcp.BootReply)
+	// Request the IP from the DHCP Server
+	p.SetCIAddr(net.ParseIP("172.10.0.2"))
+
+	expected := dhcp.ReplyPacket(p, dhcp.ACK, dhcpServer.ip, nil, 0, nil)
+	actual := dhcpServer.ServeDHCP(p, dhcp.Inform, nil)
+
+	assert.Equal(t, expected, actual)
+}