Subject: [P2PSIP] Multicast Bootstrap Issue

From: jc <[email-masked]>
Date: Fri, 23 Jul 2010 19:37:19 -0400

Hi All,
Using multicast bootstrap as loosely defined I have uncovered two problems.

1. If the RELOAD port is used for multicast group subscription then an implemented stack will give undesirable results at the message handler level. This is due to multiple sockets bound to the same port using socket option SO_REUSEADDR. The results are dropped, duplicate or unwanted messages arriving at incorrect handlers.

2. If the multicast group subscription port is not the RELOAD port the recipient of the multicast, unicast or anycast request has no way to tell which port it must contact to send a response.

10.4.  Searching for a Bootstrap Node

   ...

   The responder node that receives the Ping request SHOULD check that
   the overlay name is correct and that the requester peer sending the
   request has appropriate credentials for the overlay before responding
   to the Ping request even if the response is only an error.

If a node uses a non-reload port number for multicast group subscription the responder doesn't know which port to contact in order to send a response. It should be considered "unsafe" to assume the RELOAD port because implementors may use random port allocation or the RELOAD port may be unavailable.

Regards,
Julian Cain