wormhole pairing appid flag day 2021-12-31

Wormhole pairing will start to provide an appid to wormhole on 2021-12-31.
An appid can't be provided now because Debian stable is going to ship a
older version of git-annex that does not provide an appid. Assumption is
that by 2021-12-31, this version of git-annex will be shipped in a Debian
stable release. If that turns out to not be the case, this change will need
to be cherry-picked into the git-annex in Debian stable, or its wormhole
pairing will break.

This commit was sponsored by Thomas Hochstein on Patreon.

4 files changed, 39 insertions, 3 deletions

diff --git a/CHANGELOG b/CHANGELOG
index dde964d84..1237a2d61 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -20,6 +20,13 @@ git-annex (6.20170102) UNRELEASED; urgency=medium
     their contents in memory.
   * unused: Improved memory use significantly when there are a lot
     of differences between branches.
+  * Wormhole pairing will start to provide an appid to wormhole on
+    2021-12-31. An appid can't be provided now because Debian stable is going
+    to ship a older version of git-annex that does not provide an appid.
+    Assumption is that by 2021-12-31, this version of git-annex will be
+    shipped in a Debian stable release. If that turns out to not be the
+    case, this change will need to be cherry-picked into the git-annex in
+    Debian stable, or its wormhole pairing will break.
 
  -- Joey Hess <id@joeyh.name>  Fri, 06 Jan 2017 15:22:06 -0400
 
diff --git a/Command/P2P.hs b/Command/P2P.hs
index b70e3e2b7..505286a3d 100644
--- a/Command/P2P.hs
+++ b/Command/P2P.hs
@@ -26,6 +26,7 @@ import qualified Utility.MagicWormhole as Wormhole
 
 import Control.Concurrent.Async
 import qualified Data.Text as T
+import Data.Time.Clock.POSIX
 
 cmd :: Command
 cmd = command "p2p" SectionSetup
@@ -224,10 +225,32 @@ wormholePairing remotename ouraddrs ui = do
 		observer <- liftIO Wormhole.mkCodeObserver
 		producer <- liftIO Wormhole.mkCodeProducer
 		void $ liftIO $ async $ ui observer producer
+		-- Provide an appid to magic wormhole, to avoid using
+		-- the same channels that other wormhole users use.
+		--
+		-- Since a version of git-annex that did not provide an
+		-- appid is shipping in Debian 9, and having one side
+		-- provide an appid while the other does not will make
+		-- wormhole fail, this is deferred until 2021-12-31.
+		-- After that point, all git-annex's should have been
+		-- upgraded to include this code, and they will start
+		-- providing an appid.
+		--
+		-- This assumes reasonably good client clocks. If the clock
+		-- is completely wrong, it won't use the appid at that
+		-- point, and pairing will fail. On 2021-12-31, minor clock
+		-- skew may also cause transient problems.
+		--
+		-- After 2021-12-31, this can be changed to simply
+		-- always provide the appid.
+		now <- liftIO getPOSIXTime
+		let wormholeparams = if now < 1640950000
+			then []
+			else Wormhole.appId "git-annex.branchable.com/p2p-setup"
 		(sendres, recvres) <- liftIO $
-			Wormhole.sendFile sendf observer []
+			Wormhole.sendFile sendf observer wormholeparams
 				`concurrently`
-			Wormhole.receiveFile recvf producer []
+			Wormhole.receiveFile recvf producer wormholeparams
 		liftIO $ nukeFile sendf
 		if sendres /= True
 			then return SendFailed
diff --git a/Utility/MagicWormhole.hs b/Utility/MagicWormhole.hs
index 6d2df81e2..f9e694e28 100644
--- a/Utility/MagicWormhole.hs
+++ b/Utility/MagicWormhole.hs
@@ -18,6 +18,7 @@ module Utility.MagicWormhole (
 	waitCode,
 	sendCode,
 	WormHoleParams,
+	appId,
 	sendFile,
 	receiveFile,
 	isInstalled,
@@ -87,6 +88,11 @@ sendCode (CodeProducer p) = putMVar p
 
 type WormHoleParams = [CommandParam]
 
+-- | An appid should be provided when using wormhole in an app, to avoid
+-- using the same channel space as ad-hoc wormhole users.
+appId :: String -> WormHoleParams
+appId s = [Param "--appid", Param s]
+
 -- | Sends a file. Once the send is underway, and the Code has been
 -- generated, it will be sent to the CodeObserver. (This may not happen,
 -- eg if there's a network problem).
diff --git a/doc/bugs/tor_setup_needs_a_unique_magic-wormhole_appid.mdwn b/doc/bugs/tor_setup_needs_a_unique_magic-wormhole_appid.mdwn
index 054447ead..962466392 100644
--- a/doc/bugs/tor_setup_needs_a_unique_magic-wormhole_appid.mdwn
+++ b/doc/bugs/tor_setup_needs_a_unique_magic-wormhole_appid.mdwn
@@ -21,4 +21,4 @@ I haven't run git-annex's onion setup feature directly, but I'm reading through
 
 It looks pretty amazing! Looking forward to using it in a Dropbox-like synchronization context soon.
 
-
+> I've gone with the 2021-12-31 flag day approach. [[done]] --[[Joey]]