What Is an Interface Identifier

What is an interface identifier

First of all, you need to understand that there may be physical network cards(OR/AND logical network adapters) present in the computer to identify connection/manage connection.

Next, you have an incorrect notion about interface identifier.
What you talked about(eth,virbr,lo) are interfaces. In IPv4 addressing scheme, we don't have interface ID. We have interface ID's in IPv6 addresses.

As mentioned in The Payoff of IPv6’s Very Large Address Size

In IPv4, IP addresses have no relationship to the addresses used for underlying data link layer network technologies. A host that connects to a TCP/IP network using an Ethernet network interface card (NIC) has an Ethernet MAC address and an IP address, but the two numbers are distinct and unrelated in any way.

With the overhaul of addressing in IPv6, an opportunity presented itself to create a better way of mapping IP unicast addresses and physical network addresses. Implementing this superior mapping technique was one of the reasons why IPv6 addresses were made so large. With 128 total bits, even with a full 48 bits reserved for network prefix and 16 bits for site subnet, we are still left with 64 bits to use for the interface identifier, which is analogous to the host ID under IPv4.

Having so many bits at our disposal gives us great flexibility. Instead of using arbitrary “made-up” identifiers for hosts, we can base the interface ID on the underlying data link layer hardware address, as long as that address is no greater than 64 bits in length. Since virtually all devices use layer two addresses of 64 bits or fewer, there is no problem in using those addresses for the interface identifier in IP addresses. This provides an immediate benefit: it makes networks easier to administer, since we don't have to record two arbitrary numbers for each host. The IP address can be derived from the MAC address and the network identifier. It also means we can in the future tell the IP address from the MAC address and vice-versa.

Visit this link for more clear understanding about interface ID.

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Now,returning to clear your confusion,

all of the connections(interfaces) such as Ethernet-0,Ethernet-1,WiFi-1,etc. have their own interface identifier.You can think of them as a kind of special identification number which identifies the kind of interfaces available at that moment!

When you type ifconfig in Linux, it displays the status of the currently active interfaces.

Now,coming on the example part, let's say you have two Ethernet connections on your system, say, eth0 and eth1(these are interface names) ---so ifconfig will print these two as a result of it's output!

So,to identify these two separate interfaces,there must be an
interface identifier.The interface identifier(generally 64-bit) is
either automatically generated from the interface's MAC address using
the modified EUI-64 format, obtained from a DHCPv6 server,
automatically established randomly, or assigned manually.

Also,the interfaces which you have mentioned are some of the most-commonly used interfaces :-

'lo0', 'gif0', 'stf0', 'en0', 'en1', 'en2', 'bridge0', 'p2p0'

1. lo0---local network connection(0 for 1st connection of lan)
2. en0---ethernet connection(0,1,2 for 1st,2nd and 3rd connection on Ethernet)
3. bridge0---a bridged connection to this machine
4. p2p0---a peer-to-peer connection

don't know about gif,stf.Please note that there are logical connections/virtual connections,instead of limitation of physical connections(using NIC cards) too!

what is the difference and relationship of Interface ID, Implementations ID and DLL ID(UID3)?

All Symbian OS binaries have three UIDs: UID1, UID2, UID3.

• UID1 specifies the target category (e.g. exe, dll) and is automatically inferred from the MMP file TARGETTYPE keyword.

• UID2 specifies the target subcategory (e.g. generic dll or plug-in dll). For ECOM plug-in dlls it should be 0x10009d8d.

• UID3 identifies the object itself and you must supply an unique value (picked from unprotected range or allocated from protected range). UID2 and UID3 are specified using the MMP file UID keyword.

ECOM plug-in resource files contain three kinds of UIDs:

• dll_uid is a mechanism to map the interfaces/implementations contained in a plug-in resource file to a plug-in binary DLL. It's the same as the UID3.

• interface_uid is a UID that identifies the interface the plug-in implements. A plug-in interface may have more than one implementation so a mechanism to identify their commonality is needed.

• implementation_uid is an identifier for the interface implementation. Often it's the same as dll_uid but it doesn't need to be. It can be different to allow multiple interface implementations in a single binary.

So, UID3 is enough but the ECOM framework loding the resource files needs to know the binary dll_uid too to be able to load the implementation when requested.

How to get the Interface ID (IID, i.e. the GUID) of an interface when importing a WinRT winmd?

Short Version

The custom attribute blob is the C# serialized format of a Guid class:

3.2.2 DefineCustomAttribute

The format of pBlob for defining a custom attribute is defined in later in this spec. (broadly speaking, the blob records the argument values to the class constructor, together with zero or more values for named fields/properites – in other words, the information needed to instantiate the object specified at the time the metadata was emitted). If the constructor requires no arguments, then there is no need to provide a blob argument.

4.3.6 GetCustomAttributeProps

A custom attribute is stored as a blob whose format is understood by the metadata engine, and by Reflection; essentially a list of argument values to a constructor method which will create an instance of the custom attribute.

In order to get the GuidAttriute guid value, you have to emulate C#'s deserializing a Guid object from a stream.

Long Version

Starting with your IMetadataImport you call IMetaDataImport.GetCustomAttributeByName.

The first tricky part is figuring out the name of the attribute I'm after. I know it's Guid when viewed in IDL or C#:

[Guid("CA30221D-86D9-40FB-A26B-D44EB7CF08EA")]
interface ICalendar
{
    //...
}

And that underneath it would actually be called "GuidAttribute". But neither of those actually work:

• "Guid": Fails with S_FALSE
• "GuidAttribute": Fails with S_FALSE

You might try the full name of the attribute class:

• "System.Runtime.InteropServices.GuidAttribute"

But that also fails because that's the name of the GuidAttribute class in the .NET framework. In the WinRT library you have to use "Windows.Foundation.Metadata.GuidAttribute":

• "Guid": Fails with S_FALSE
• "GuidAttribute": Fails with S_FALSE
• "System.Runtime.InteropServices.GuidAttribute": Fails with S_FALSE (CLR only)
• "Windows.Foundation.Metadata.GuidAttribute": Works

Now that we figured out the name of the attribute to find, we can query for it:

mdToken calendarTokenID = 0x02000022; //Windows.Globalization.ICalendar
String  attributeName   = "Windows.Foundation.Metadata.GuidAttribute";

Pointer blob;
UInt32 blobLen;
reader.GetCustomAttributeByName(calendarTokenID, attributeName, out blob, out blobLen);

The next tricky part is is decoding the blob.

Decoding the blob

Custom attributes each have a different serialization formats. The blob is essentially passed to the Attribute's constructor. The serialization format is the same as the C# serialization format.

For GuidAttribute attributes, the binary serialization format is 20-bytes:

01 00                                            Prolog (2-bytes)       0x0001 ==> version 1
1D 22 30 CA D9 86 FB 40 A2 6B D4 4E B7 CF 08 EA  Guid (16-bytes)        "CA30221D-86D9-40FB-A26B-D44EB7CF08EA"
00 00                                            Trailing null (2-bytes)

The easiest way for me to extract the Guid is to declare a matching structure, cast the returned pointer to a type of that structure, and access the Guid member:

struct SerializedGuidAttribute
{
   UInt16 prolog; //2-bytes. 0x0001 
   Guid   guid;   //16-byte guid
   UInt16 footer; //2-byte footer
}
typedef SerializedGuidAttribute* PSerializedGuidAttribute;

Guid guidAttriute = PSerializedGuidAttribute(blob).guid;

And you have it

Guid GetGuidAttribute(IMetadataReader reader, mdToken intf)
{
   Pointer blob;
   UInt32 blobLen;
   reader.GetCustomAttributeByName(intf, "Windows.Foundation.Metadata.GuidAttribute", 
         out blob, out blobLen);

   //if (blobLen != 20) { throw new Exception("Something") };

   return PSerializedGuidAttribute(blob).guid;
}

Bonus

• Microsoft Metadata API documentation
  
  
  • 9/8/2000: .docx
  • 8/2/2001: .pdf

Typescript Interface SyntaxError: Unexpected identifier at interface name

There is no Typescript syntax error in your code. You can see that it has no errors at all in the Typescript playground.

But from the stacktrace it appears that you are trying to execute the Typescript directly as a Javascript CommonJS module? That would explain the error because Javascript does not support interfaces; that's a Typescript thing.

I can't help you more without you providing more info about your setup, the command you executed that produced that error, etc.

illegal interface identifier

There's no need to use that statement here. Remove this statement from your .m(implementation) file and that will do it.

@synthesize theservices;

Remove this. Only properties that are declared in the .h files have to be synthesised. And that too is optional. You need to remove this and just directly use theservices variable in your .m file

Unique identifier for every interface-implementation

If you know there's ever going to be at most one instance per implementing class, then using the Class object as the key is a pretty natural solution.

If you don't, then clearly the IDs would have to be instance-specific and not class-specific.

How can I find the typelib identifier of the DirectShow interfaces for use with COM4j

Loathe as I am to provide a link that might be dead tomorrow, the only help I found was this site which contains a link to a tlb file for the DirectShow interfaces. The COM4j library can interact with this file to generate its interfaces.

Curiously, it didn't create a ClassFactory method for creating the interface I needed, possibly because the ClassFactory naming convention is to name a method 'createXXX' where XXX is the name of the interface, and the interface in question is createDevEnum. However a little manual tweaking to the ClassFactory class fixed this.

ArrayList return type in generic interface - identifier expected

You are just specifying the return-type and the arguments that this method take. public ArrayList<T> (int page, int count) throws SQLException;. But where are you specifying the name of the method?

As you are missing the name of the method, you are getting this compile-time error.

Just few more note points:

• You should return java.util.List instead of a specific type (java.util.ArrayList)
• You don't need to prefix your interface name with I. That is a convention followed in C#
• Method names in Java must preferably be starting with a lower-case character (and follow camel-case notation).

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