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Added support for two new PIM message Types(rfc9465)

Ananya requested to merge agopal4/wireshark:add_rfc9465 into master

Problem: This is an enhancement to accommodate the new packet types defined in RFC9465. Component is PIM - Protocol Independent Multicast. So far, PIM has 12 Message Types defined. The Two new types are 13.0 and 13.1. Also IANA assigned a special bit in the existing Register-Stop message (Type 2) to advertise RFC9465 protocol support to other routers.

Note: Up until PIM message type 12, only 4 bits were used to identify a PIM message. This is the “Type” field. However this is proving to be insufficient for the increasing number of types, hence IANA is now assigning the Subtype (4 bits) field as well to identify new and future PIM messages.

The new message types are PIM Packed Null-Register message (Type 13.0) and PIM Packed Register-Stop message (Type 13.1). Each of these messages also have (G,S) information, in a batched format. Kindly check the “overview section”, added screenshots of how outputs look like.

Also, PIM_BIDIR_RSVD is not being used anywhere, made it A generic macro to extract subtype that can be used for all packet types in the future.

More about the protocol: RFC9465 provides support for PIM Null-Register Packing. Before this RFC, PIM message types 1 and 2 could only send information about a single multicast source and group. With this RFC, routers are capable of batching records into a single packet.

Message Type 1 indicates a Register packet for a single (S,G) Message Type 2 indicates a Register-Stop packet for a single (S,G)

With this Merge Request, Message Type 13.0 will be identified by Wireshark as Register packet for MULTIPLE (S,G)s and Message Type 13.1, as a Register-Stop packet for MULTIPLE (S,G)s.

Important to note that PIM will start using the 8 bits (Type:4, subtype:4) to identify the message type. This is because the original Type:4 is seemingly insufficient to identify new packet types.

Summary: Three major changes in this merge request:

  1. Routers have to to indicate RFC9465 capability using a IANA assigned bit in the existing PIM Message Type 2. (PIM_REGISTER_STOP)
  2. Packet Type 13, and subtype 0 = Packed Null-Register message.
  3. Packet Type 13, and subtype 1 = Packed Register-Stop message.

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