Not thread safe on Linux?

[bryanlarsen]

We're having problems with sporadically failing unit tests on Linux; it appears to happen because unit tests in Rust happen in parallel. Each unit test create's their own NetRoute handle to manipulate and query routes, and occasionally we experience strange failures.

The errors vary between runs, but this one seems particularly indicative:

called `Result::unwrap()` on an `Err` value: IO(Custom { kind: Other, error: "Received an unexpected message NetlinkMessage { header: NetlinkHeader { length: 116, message_type: 25, flags: 0, sequence_number: 5, port_number: 27472 }, payload: InnerMessage(DelRoute(RouteMessage { header: RouteHeader { address_family: Inet6, destination_prefix_length: 120, source_prefix_length: 0, tos: 0, table: 254, protocol: Static, scope: Universe, kind: Unicast, flags: [] }, attributes: [Table(254), Destination(Inet6(::8000)), Priority(1024), Oif(1), CacheInfo(RouteCacheInfo { clntref: 0, last_use: 0, expires: 0, error: 0, used: 0, id: 0, ts: 0, ts_age: 0 }), Preference(Medium)] })) }" }, "NetRoute::get")

The error happened on a .list() call in an IPV4 unit test. Running in parallel is an IPV6 unit test that add's and removes a ::8000/120 route.