scionproto-contrib/jpan

ScmpEchoDemo fails with some "minimal" destinations

Closed this issue · 2 comments

tzaeschke commented

When running the ScmpEchoDemo with the minimal topology, the default AS 211 can be reached, but AS 111 times out and AS 1111 causes an Exception.

Initial analysis

  • AS 111 appears to be broken because 111 is an on-path AS. The current path creation algorithm does not recognize that and create an UP+DOWN path. This appears to irritate the BR in 111 and the packet is dropped. This should be resolved with the implementation of on-path path creation.
  • AS 1111 appears to be broken because the echo process listens on 0.0.0.0. This somehow confuses the border router and the packet cannot be returned (port unreachable). Temporary resolution: provide a better error message (implemented in #97). Long term solution: fix problem, e.g. by binding to a proper IP address. Side note: 0.0.0.0 is not an IPv4 address but an IPv6 mapped address (check netstat). Also: it seems this problem is limited to topologies running locally on the machine, echo in the production network is not affected.
tzaeschke commented

Shortcut + on-path was fixed in #104

tzaeschke commented

Part one is fixed. Path 2 is unclear. Won't fix, works in production, fails only in local minimal setup.