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more protocol docs updates

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Brian Warner 2018-07-01 21:14:21 -07:00
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docs/dilation-protocol.md
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@ -11,14 +11,24 @@ connection has been lost, and then coordinate the construction of a
replacement. Within this connection, a series of queued-and-acked subchannel replacement. Within this connection, a series of queued-and-acked subchannel
messages are used to open/use/close the application-visible subchannels. messages are used to open/use/close the application-visible subchannels.
## Versions and can-dilate
The Wormhole protocol includes a `versions` message sent immediately after
the shared PAKE key is established. This also serves as a key-confirmation
message, allowing each side to confirm that the other side knows the right
key. The body of the `versions` message is a JSON-formatted string with keys
that are available for learning the abilities of the peer. Dilation is
signaled by a key named `can-dilate`, whose value is a list of strings. Any
version present in both side's lists is eligible for use.
## Leaders and Followers ## Leaders and Followers
Each side of a Wormhole has a randomly-generated dilation "side" string (this Each side of a Wormhole has a randomly-generated dilation `side` string (this
is independent of the Wormhole's mailbox "side"). When the wormhole is is included in the `please-dilate` message, and is independent of the
dilated, the side with the lexicographically-higher "side" value is named the Wormhole's mailbox "side"). When the wormhole is dilated, the side with the
"Leader", and the other side is named the "Follower". The general wormhole lexicographically-higher "side" value is named the "Leader", and the other
protocol treats both sides identically, but the distinction matters for the side is named the "Follower". The general wormhole protocol treats both sides
dilation protocol. identically, but the distinction matters for the dilation protocol.
Both sides send a `please-dilate` as soon as dilation is triggered. Each side Both sides send a `please-dilate` as soon as dilation is triggered. Each side
discovers whether it is the Leader or the Follower when the peer's discovers whether it is the Leader or the Follower when the peer's
@ -28,6 +38,15 @@ potential connections to use, the Leader decides which one to use, and the
Leader gets to decide when the connection is no longer viable (and triggers Leader gets to decide when the connection is no longer viable (and triggers
the establishment of a new one). the establishment of a new one).
The `please-dilate` includes a `use-version` key, computed as the "best"
version of the intersection of the two sides' abilities as reported in the
`versions` message. Both sides will use whichever `use-version` was specified
by the Leader (they learn which side is the Leader at the same moment they
learn the peer's `use-version` value). If the Follower cannot handle the
`use-version` value, dilation fails (this shouldn't happen, as the Leader
knew what the Follower was and was not capable of before sending that
message).
## Connection Layers ## Connection Layers
We describe the protocol as a series of layers. Messages sent on one layer We describe the protocol as a series of layers. Messages sent on one layer