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r13801@catbus: nickm | 2007-07-17 13:49:12 -0400

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More tweaks to dir-spec.txt; not complete, but closing in.


svn:r10856
This commit is contained in:
Nick Mathewson 2007-07-17 17:49:16 +00:00
parent a1ab2c8087
commit 670db47e1b
3 changed files with 84 additions and 23 deletions
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104
doc/spec/dir-spec.txt
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@ -297,6 +297,29 @@ $Id$
The "Digest" of a document, unless stated otherwise, is its digest *as
signed by this signature scheme*.
1.4. Voting timeline
Every consensus document has a "valid-after" (VA) time, a "fresh-until"
(FU) time and a "valid-until" (VU) time. VA MUST precede FU, which MUST
in turn precede VU. Times are chosen so that every consensus will be
"fresh" until the next consensus becomes valid, and "valid" for a while
after. At least 2 or 3 consensuses should be valid at any given time.
The timeline for a given consensus is as follows:
VA-DistSeconds-VoteSeconds: The authorities exchange votes.
VA-DistSeconds: The authorities calculate the consensus and exchange
signatures.
VA: All authorities have a multiply signed consensus.
VA ... FU: Caches download the consensus.
FU: The consensus is no long the freshest consensus.
VU: The consensus is no longer valid.
2. Router operation and formats
ORs SHOULD generate a new router descriptor and a new extra-info
@ -696,6 +719,14 @@ $Id$
The status MUST be "vote" or "consensus", depending on the type of
the document.
"consensus-methods" SP IntegerList NL
[Exactly once for votes; does not occur in consensuses.]
A space-separated list of supported methods for generating
consensuses from votes. See section 3.4.1 for details. Method "1"
MUST be included.
"published" SP YYYY-MM-DD SP HH:MM:SS NL
[Exactly once for votes; does not occur in consensuses.]
@ -706,25 +737,34 @@ $Id$
[Exactly once.]
The start of the Interval for this vote. XXXX
The start of the Interval for this vote. Before this time, the
consensus document produced from this vote should not be used.
See 1.4 for voting timeline information.
"fresh-until" SP YYYY-MM-DD SP HH:MM:SS NL
[Exactly once.]
XXXX
The time at which the next consensus should be produced; before this
time, there is no point in downloading another consensus, since there
won't be a new one. See 1.4 for voting timeline information.
"valid-until" SP YYYY-MM-DD SP HH:MM:SS NL
[Exactly once.]
The end of the Interval for this vote. XXXX
The end of the Interval for this vote. After this time, the
consensus produced by this vote should not be used. See 1.4 for
voting timeline information.
"voting-delay" SP VoteSeconds SP DistSeconds NL
[Exactly once.]
XXXX
VoteSeconds is the number of seconds that we will allow to collect
votes from all authorities; DistSeconds is the number of seconds
we'll allow to collect signatures from all authorities. See 1.4 for
voting timeline information.
"client-versions" SP VersionList NL
@ -980,6 +1020,22 @@ $Id$
The signatures at the end of a consensus document are sorted in
ascending order by identity digest.
3.4.1. Forward compatibility
Future versions of Tor will need to include new information in the
consensus documents, but it is important that all authorities (or at least
half) generate and sign the same signed consensus.
To achieve this, authorities list in their votes their supported methods
for generating consensuses from votes. The method described above and
implemented in Tor 0.2.0.x is "1". Later methods will be assigned higher
numbers.
Before generating a consensus, an authority must decide which consensus
method to use. To do this, it looks for the highest version number
supported by more than 2/3 of the authorities. If it supports this
method, then it uses it. Otherwise, it falls back to method 1.
3.5. Detached signatures
Assuming full connectivity, every authority should compute and sign the
@ -1061,17 +1117,15 @@ $Id$
merged with the second-to-last period.
An authority SHOULD publish its vote immediately at the start of each voting
period. It does this by making it available at
period (minus VoteSeconds+DistSeconds). It does this by making it
available at
http://<hostname>/tor/status-vote/current/authority.z
and sending it in an HTTP POST request to each other authority at the URL
http://<hostname>/tor/post/vote
(Note that this requires the authority to settle upon and finalize its
vote slightly before the start of the voting period.)
If, VOTING_DELAY minutes after the voting period has begun, an authority
If, at the start of the voting period, minus DistSeconds, an authority
does not have a current statement from another authority, the first
authority retrieves the other's statement.
authority downloads the other's statement.
Once an authority has a vote from another authority, it makes it available
at
@ -1080,9 +1134,15 @@ $Id$
The consensus status, along with as many signatures as the server
currently knows, should be available at
http://<hostname>/tor/status-vote/current/consensus.z
http://<hostname>/tor/status-vote/next/consensus.z
All of the detached signatures it knows for consensus status should be
available at:
http://<hostname>/tor/status-vote/next/consensus-signatures.z
Once there are enough signatures, or once the voting period starts,
these documents are available at
http://<hostname>/tor/status-vote/current/consensus.z
and
http://<hostname>/tor/status-vote/current/consensus-signatures.z
Once an authority has computed and signed a consensus network status, it
@ -1095,17 +1155,17 @@ $Id$
[XXX possible future features include support for downloading old
consensuses.]
[XXX Constants: VOTING_DELAY, CONSENSUS_DELAY]
4.3. Downloading consensus status documents (caches only)
All directory servers (authorities and caches) try to keep a fresh
set of network-status consensus documents to serve to clients. Every
15 minutes, or whenever the valid-until field on its most current
consensus is about to expire
[XXXX finish this section]
All directory servers (authorities and caches) try to keep a recent
network-status consensus document to serve to clients. A cache ALWAYS
downloads a network-status consensus if any of the following are true:
- The cache has no consensus document.
- The cache's consensus document is no longer valid.
Otherwise, the cache downloads a new consensus document at a randomly
chosen time after its current consensus stops being fresh. (This time is
chosen at random to avoid swarming the authorities at the start of each
period.)
4.4. Downloading and storing router descriptors (authorities and caches)
@ -1251,14 +1311,12 @@ $Id$
until it has a live network-status consensus document, and it has
descriptors for more than 1/4 of the routers that it believes are running.
[XXXX handling clock skew at client side?]
[XXXX fall-back to most recent?]
(Note: clients can and should pick caches based on the network-status
information they have: once they have first fetched network-status info
from an authority, they should not need to go to the authority directly
again.)
5.2. Downloading and storing router descriptors
Clients try to have the best descriptor for each router. A descriptor is

1
src/or/dirserv.c
View File

@ -1948,6 +1948,7 @@ format_networkstatus_vote(crypto_pk_env_t *private_signing_key,
tor_snprintf(status, len,
"network-status-version 3\n"
"vote-status vote\n"
"consensus-methods 1\n"
"published %s\n"
"valid-after %s\n"
"fresh-until %s\n"

2
src/or/routerparse.c
View File

@ -75,6 +75,7 @@ typedef enum {
K_KNOWN_FLAGS,
K_VOTE_DIGEST,
K_CONSENSUS_DIGEST,
K_CONSENSUS_METHODS,
_UNRECOGNIZED,
_ERR,
@ -307,6 +308,7 @@ static token_rule_t networkstatus_vote_token_table[] = {
T1( "known-flags", K_KNOWN_FLAGS, CONCAT_ARGS, NO_OBJ ),
T01("client-versions", K_CLIENT_VERSIONS, CONCAT_ARGS, NO_OBJ ),
T01("server-versions", K_SERVER_VERSIONS, CONCAT_ARGS, NO_OBJ ),
T1( "consensus-methods", K_CONSENSUS_METHODS, GE(1), NO_OBJ ),
END_OF_TABLE
};