From e8bf5d10483e998be394d9a8c407849f672ef9b2 Mon Sep 17 00:00:00 2001
From: Bastien Teinturier <31281497+t-bast@users.noreply.github.com>
Date: Thu, 8 Oct 2020 11:07:27 +0200
Subject: [PATCH] [OpenChannel] Use TLV for channel version (#1534)

We were previously using an encoding that was incompatible with TLV.
We keep the old format, but also understand the channel version when provided
in a TLV field.

If the old format is provided, it will be preferred.
---
 .../fr/acinq/eclair/wire/ChannelTlv.scala     |  4 ++++
 .../fr/acinq/eclair/wire/OpenTlvSpec.scala    | 19 ++++++++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/wire/ChannelTlv.scala b/eclair-core/src/main/scala/fr/acinq/eclair/wire/ChannelTlv.scala
index 4c7b30041..982c06319 100644
--- a/eclair-core/src/main/scala/fr/acinq/eclair/wire/ChannelTlv.scala
+++ b/eclair-core/src/main/scala/fr/acinq/eclair/wire/ChannelTlv.scala
@@ -45,7 +45,11 @@ object OpenChannelTlv {
 
   val openTlvCodec: Codec[TlvStream[OpenChannelTlv]] = tlvStream(discriminated[OpenChannelTlv].by(varint)
     .typecase(UInt64(0), variableSizeBytesLong(varintoverflow, bytes).as[UpfrontShutdownScript])
+    // TODO: @t-bast: once enough active Phoenix users have upgraded to versions > 1.3.3, we should configure the ACINQ
+    // node to write with the new encoding (0x47000001).
+    // Once that's done, we can remove the old encoding below (0x47000000) for future Phoenix upgrades.
     .typecase(UInt64(0x47000000), bits(ChannelVersion.LENGTH_BITS).as[ChannelVersion].as[ChannelVersionTlv])
+    .typecase(UInt64(0x47000001), variableSizeBytesLong(varintoverflow, bits(ChannelVersion.LENGTH_BITS)).as[ChannelVersion].as[ChannelVersionTlv])
   )
 
 }
diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/wire/OpenTlvSpec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/wire/OpenTlvSpec.scala
index 372fe5f8e..0a5272388 100644
--- a/eclair-core/src/test/scala/fr/acinq/eclair/wire/OpenTlvSpec.scala
+++ b/eclair-core/src/test/scala/fr/acinq/eclair/wire/OpenTlvSpec.scala
@@ -19,19 +19,24 @@ package fr.acinq.eclair.wire
 import fr.acinq.eclair.channel.ChannelVersion
 import fr.acinq.eclair.wire.OpenChannelTlv.ChannelVersionTlv
 import org.scalatest.funsuite.AnyFunSuite
-import scodec.{Attempt, DecodeResult}
 import scodec.bits._
+import scodec.{Attempt, DecodeResult}
 
 class OpenTlvSpec extends AnyFunSuite {
 
   test("channel version tlv") {
-
-    val refs = Map(
-      ChannelVersion.STANDARD -> hex"fe47000000 00000001".bits,
-      (ChannelVersion.STANDARD | ChannelVersion.ZERO_RESERVE) -> hex"fe47000000 00000009".bits
+    case class TestCase(expected: ChannelVersion, encoded: BitVector, reEncoded: BitVector)
+    val testCases = Seq(
+      TestCase(ChannelVersion.STANDARD, hex"fe47000000 00000001".bits, hex"fe47000000 00000001".bits),
+      TestCase(ChannelVersion.STANDARD, hex"fe47000001 04 00000001".bits, hex"fe47000000 00000001".bits),
+      TestCase(ChannelVersion.STANDARD | ChannelVersion.ZERO_RESERVE, hex"fe47000000 00000009".bits, hex"fe47000000 00000009".bits),
+      TestCase(ChannelVersion.STANDARD | ChannelVersion.ZERO_RESERVE, hex"fe47000001 04 00000009".bits, hex"fe47000000 00000009".bits)
     )
 
-    refs.foreach { case (cv, bits) => assert(OpenChannelTlv.openTlvCodec.encode(TlvStream(ChannelVersionTlv(cv))) === Attempt.Successful(bits)) }
-    refs.foreach { case (cv, bits) => assert(OpenChannelTlv.openTlvCodec.decode(bits) === Attempt.successful(DecodeResult(TlvStream(ChannelVersionTlv(cv)), BitVector.empty))) }
+    for (testCase <- testCases) {
+      assert(OpenChannelTlv.openTlvCodec.decode(testCase.encoded) === Attempt.successful(DecodeResult(TlvStream(ChannelVersionTlv(testCase.expected)), BitVector.empty)))
+      assert(OpenChannelTlv.openTlvCodec.encode(TlvStream(ChannelVersionTlv(testCase.expected))) === Attempt.Successful(testCase.reEncoded))
+    }
   }
+
 }
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