This introduces new client and server halves to the Introducer (renaming the
old one with a _V1 suffix). Both have fallbacks to accomodate talking to a
different version: the publishing client switches on whether the server's
.get_version() advertises V2 support, the server switches on which
subscription method was invoked by the subscribing client.
The V2 protocol sends a three-tuple of (serialized announcement dictionary,
signature, pubkey) for each announcement. The V2 server dispatches messages
to subscribers according to the service-name, and throws errors for invalid
signatures, but does not otherwise examine the messages. The V2 receiver's
subscription callback will receive a (serverid, ann_dict) pair. The
'serverid' will be equal to the pubkey if all of the following are true:
the originating client is V2, and was told a privkey to use
the announcement went through a V2 server
the signature is valid
If not, 'serverid' will be equal to the tubid portion of the announced FURL,
as was the case for V1 receivers.
Servers will create a keypair if one does not exist yet, stored in
private/server.privkey .
The signed announcement dictionary puts the server FURL in a key named
"anonymous-storage-FURL", which anticipates upcoming Accounting-related
changes in the server advertisements. It also provides a key named
"permutation-seed-base32" to tell clients what permutation seed to use. This
is computed at startup, using tubid if there are existing shares, otherwise
the pubkey, to retain share-order compatibility for existing servers.
It is currently hardcoded in setup.py to be 'allmydata-tahoe'. Ticket #556 is to make it configurable by a runtime command-line argument to setup.py: "--appname=foo", but I suddenly wondered if we really wanted that and at the same time realized that we don't need that for tahoe-1.3.0 release, so this patch just hardcodes it in setup.py.
setup.py inspects a file named 'src/allmydata/_appname.py' and assert that it contains the string "__appname__ = 'allmydata-tahoe'", and creates it if it isn't already present. src/allmydata/__init__.py import _appname and reads __appname__ from it. The rest of the Python code imports allmydata and inspects "allmydata.__appname__", although actually every use it uses "allmydata.__full_version__" instead, where "allmydata.__full_version__" is created in src/allmydata/__init__.py to be:
__full_version__ = __appname + '-' + str(__version__).
All the code that emits an "application version string" when describing what version of a protocol it supports (introducer server, storage server, upload helper), or when describing itself in general (introducer client), usese allmydata.__full_version__.
This fixes ticket #556 at least well enough for tahoe-1.3.0 release.
