The main purpose of this is to set an upper bound on the rate at which
an attacker might execute a brute force attack on the weave password.
No need to get clever or precise here.
Closes#837.
Topology gossip can be received on a connection before that connection
has been marked as 'established'. If we do not include unestablished
connections in topology gossip, then parts of the topology can be
removed by gc, since they are deemed unreachable, which can cause
subsequent incremental topology gossips to be rejected due to them
containing references to peers that have been removed by the gc.
Including unestablished connections in topology gossip requires:
- removing the check for 'established' connections in the encoding of
peers for topology gossip,
- adding the 'established' flag to the internal representation of
remote connections,
- adding the 'established' flag to to encoding of connections in
topology gossip,
- treating the *addition* of a connection as an update to the local
peer.
The latter entails
- bumping the peer version on connection addition (as well as on
marking 'established' as previously),
- bumping the peer version *unconditionally* on connection deletion
(rather than only when the connection was 'established', as
previously),
- moving the initial sending of complete topology on the connection,
and the broadcasting of a topology update containing the two peers
at the ends of the connection, from the connection 'established'
logic to the connection addition logic,
- broadcasting just an topology update for the local peer when a
connection gets marked as 'established',
- broadcasting a topology update for the local peer *unconditionally*
when a connection is removed (rather than only doing this when the
connection was 'established', as previously).
When an update contains an older version of a peer we know about,
there is no point in including our better version in the "improved"
update, since we will have told our neighbours about that already and
any race conditions are taken care off by the periodic sending of the
complete topology.
The latter is the most secure route since it keeps the password
completely out of any command lines, and the permissions on the file
can be very restrictive, e.g. 0400.
It would be somewhat nicer if the password file contained just
<password>
rather than
WEAVE_PASSWORD=<password>
but then we'd have to transit the password via a temporary file with
0600 permissions.
Adam Harrison