Previously, if LocalConnection run() failed before calling
AddConnection, it would not gossip anything. This was benign, because
the peer information we learn in the handshake is just a placeholder
until the full information arrived via gossip, and if a connection is
not formed, there is nothing else to gossip about.
With short ids, there's a corner case where this is no longer true: If
a new peer connects to us, and it has the same short id as we do, then
we might change our short id. If we do, then it is important that we
gossip that out, even if the attempt to establish the connection fails
further along.
These are needed to support vxlan encapsulation. In a vxlan packet,
the only place we can straightforwardly hold the source and
destination peers identifiers used by the weave router is in the
24-bit VNI (vxlan network identifier) field. This gives us 12 bits to
indicate a peer. The resulting limit of 4096 peers on a weave network
does not seem like a problem in the near future. But it does mean
that decentralized allocation makes collisions fairly likely even in
weave networks of sizes that are common today. Fortunately, the
problem is much more tractable than IPAM because we can detect when
collisions occur and take action to resolve them.
TODO: We already notify the InterHost when a short id -> peer mapping
changes, but we also need to flush any entries in the router MAC cache
that might be affected.
From the golang spec: 'A "break" statement terminates execution of the
innermost "for", "switch", or "select" statement within the same
function.' But the LocalConnection actorLoop seems to assume it
skips the "select" and terminates the enclosing "for".
As a result, if something did conn.Shutdown(nil), it would not actually
shutdown the connection. It turns out this is never a problem, because
Shutdown is always called with a non-nil error, even though there is code
in a few places to handle the nil case. By cleaning that up, the dubious
"break" is eliminated.
Using the Ring CRDT and Weave gossip, provides an interface
for the weave script to allocate IP addresses in `weave run`,
`weave start` and `weave expose`.
See docs/ipam.md for implementation details, and site/features.md
for user-visible changes.
- get rid of individual Peer locks
- hold Peers read (or write) lock and LocalPeer read lock while
performing route calculations
This eliminates the deadlock resulting from the inconsistent lock
acquisition order in route calculcation.
Fixes#643.
This makes for a more symmetric API - Peers.FetchWithDefault does the
increment and Peers.Dereference does the decrement, whereas previously
the latter was done by Peer.DecrementLocalRefCount.
This does increase lock granularity, i.e. modifying any ref count now
requires a write lock on Peers.
When we want a string representation of a Peer, we nearly always just
want the full name. So make String() return that and introduce Info()
to return expanded info.
David Wragg