Retrieve Epoch from ChainID (#7280)

* add functions to parse epoch from height

* remove 0 epoch hardcoding

* fix tendermint tests

* fix tests

* start update docs

* progress

* better parsing of chainID

* fix update and misbehaviour logic and add tests

* update docs

* docfix

* Apply suggestions from code review

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>

* Update x/ibc/07-tendermint/types/misbehaviour_handle_test.go

* change self checks to use epochs

* address rest of reviews

* rename epoch number to version in docs

* wrap up rest of TODOs

* Update x/ibc/02-client/genesis.go

* add self validate test

* Apply suggestions from code review

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>

* fix godoc

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>

x/ibc/02-client/client/utils/utils.go

@@ -115,7 +115,6 @@ func QueryConsensusStateABCI(
 		return nil, err
 	}
 
-	// TODO: retrieve epoch-number from chain-id
 	return types.NewQueryConsensusStateResponse(clientID, anyConsensusState, proofBz, proofHeight), nil
 }
 

x/ibc/02-client/genesis.go

@@ -45,10 +45,9 @@ func InitGenesis(ctx sdk.Context, k keeper.Keeper, gs types.GenesisState) {
 	}
 
 	// client id is always "localhost"
-	// Hardcode 0 as epoch number for now
+	epoch := types.ParseChainID(ctx.ChainID())
-	// TODO: Retrieve epoch from chain-id
 	clientState := localhosttypes.NewClientState(
-		ctx.ChainID(), types.NewHeight(0, uint64(ctx.BlockHeight())),
+		ctx.ChainID(), types.NewHeight(epoch, uint64(ctx.BlockHeight())),
 	)
 
 	_, err := k.CreateClient(ctx, exported.ClientTypeLocalHost, clientState, nil)

x/ibc/02-client/keeper/client_test.go

@@ -7,6 +7,7 @@ import (
 	tmtypes "github.com/tendermint/tendermint/types"
 
 	"github.com/cosmos/cosmos-sdk/x/ibc/02-client/types"
+	clienttypes "github.com/cosmos/cosmos-sdk/x/ibc/02-client/types"
 	ibctmtypes "github.com/cosmos/cosmos-sdk/x/ibc/07-tendermint/types"
 	localhosttypes "github.com/cosmos/cosmos-sdk/x/ibc/09-localhost/types"
 	commitmenttypes "github.com/cosmos/cosmos-sdk/x/ibc/23-commitment/types"
@@ -60,11 +61,17 @@ func (suite *KeeperTestSuite) TestCreateClient() {
 func (suite *KeeperTestSuite) TestUpdateClientTendermint() {
 	// Must create header creation functions since suite.header gets recreated on each test case
 	createFutureUpdateFn := func(s *KeeperTestSuite) *ibctmtypes.Header {
-		return ibctmtypes.CreateTestHeader(testChainID, int64(suite.header.GetHeight().GetEpochHeight()+3), int64(suite.header.GetHeight().GetEpochHeight()), suite.header.Header.Time.Add(time.Hour),
+		heightPlus3 := clienttypes.NewHeight(suite.header.GetHeight().GetEpochNumber(), suite.header.GetHeight().GetEpochHeight()+3)
+		height := suite.header.GetHeight().(clienttypes.Height)
+
+		return ibctmtypes.CreateTestHeader(testChainID, heightPlus3, height, suite.header.Header.Time.Add(time.Hour),
 			suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
 	}
 	createPastUpdateFn := func(s *KeeperTestSuite) *ibctmtypes.Header {
-		return ibctmtypes.CreateTestHeader(testChainID, int64(suite.header.GetHeight().GetEpochHeight()-2), int64(suite.header.GetHeight().GetEpochHeight())-4, suite.header.Header.Time,
+		heightMinus2 := clienttypes.NewHeight(suite.header.GetHeight().GetEpochNumber(), suite.header.GetHeight().GetEpochHeight()-2)
+		heightMinus4 := clienttypes.NewHeight(suite.header.GetHeight().GetEpochNumber(), suite.header.GetHeight().GetEpochHeight()-4)
+
+		return ibctmtypes.CreateTestHeader(testChainID, heightMinus2, heightMinus4, suite.header.Header.Time,
 			suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
 	}
 	var (
@@ -270,6 +277,7 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 	altTime := suite.ctx.BlockTime().Add(time.Minute)
 
 	heightPlus3 := types.NewHeight(0, height+3)
+	heightPlus5 := types.NewHeight(0, height+5)
 
 	testCases := []struct {
 		name         string
@@ -280,8 +288,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"trusting period misbehavior should pass",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height, height, altTime, bothValSet, bothValSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, altTime, bothValSet, bothValSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height, height, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -297,8 +305,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"misbehavior at later height should pass",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height+5, height, altTime, bothValSet, valSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, testClientHeight, altTime, bothValSet, valSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height+5, height, suite.ctx.BlockTime(), bothValSet, valSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, testClientHeight, suite.ctx.BlockTime(), bothValSet, valSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -324,8 +332,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"misbehavior at later height with different trusted heights should pass",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height+5, height, altTime, bothValSet, valSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, testClientHeight, altTime, bothValSet, valSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height+5, height+3, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, heightPlus3, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -351,8 +359,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"trusted ConsensusState1 not found",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height+5, height+3, altTime, bothValSet, bothValSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, heightPlus3, altTime, bothValSet, bothValSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height+5, height, suite.ctx.BlockTime(), bothValSet, valSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, testClientHeight, suite.ctx.BlockTime(), bothValSet, valSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -368,8 +376,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"trusted ConsensusState2 not found",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height+5, height, altTime, bothValSet, valSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, testClientHeight, altTime, bothValSet, valSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height+5, height+3, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, heightPlus5, heightPlus3, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -391,8 +399,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"client already frozen at earlier height",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height, height, altTime, bothValSet, bothValSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, altTime, bothValSet, bothValSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height, height, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, suite.ctx.BlockTime(), bothValSet, bothValSet, bothSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},
@@ -411,8 +419,8 @@ func (suite *KeeperTestSuite) TestCheckMisbehaviourAndUpdateState() {
 		{
 			"misbehaviour check failed",
 			&ibctmtypes.Misbehaviour{
-				Header1:  ibctmtypes.CreateTestHeader(testChainID, height, height, altTime, bothValSet, bothValSet, bothSigners),
+				Header1:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, altTime, bothValSet, bothValSet, bothSigners),
-				Header2:  ibctmtypes.CreateTestHeader(testChainID, height, height, suite.ctx.BlockTime(), altValSet, bothValSet, altSigners),
+				Header2:  ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeight, suite.ctx.BlockTime(), altValSet, bothValSet, altSigners),
 				ChainId:  testChainID,
 				ClientId: testClientID,
 			},

x/ibc/02-client/keeper/keeper.go

@@ -189,14 +189,15 @@ func (k Keeper) GetClientConsensusStateLTE(ctx sdk.Context, clientID string, max
 
 // GetSelfConsensusState introspects the (self) past historical info at a given height
 // and returns the expected consensus state at that height.
-// TODO: Replace height with *clienttypes.Height once interfaces change
+// For now, can only retrieve self consensus states for the current epoch
 func (k Keeper) GetSelfConsensusState(ctx sdk.Context, height exported.Height) (exported.ConsensusState, bool) {
-	// TODO: check self chain-id against epoch number
 	selfHeight, ok := height.(types.Height)
 	if !ok {
 		return nil, false
 	}
-	if selfHeight.EpochNumber != 0 {
+	// check that height epoch matches chainID epoch
+	epoch := types.ParseChainID(ctx.ChainID())
+	if epoch != height.GetEpochNumber() {
 		return nil, false
 	}
 	histInfo, found := k.stakingKeeper.GetHistoricalInfo(ctx, int64(selfHeight.EpochHeight))
@@ -214,6 +215,7 @@ func (k Keeper) GetSelfConsensusState(ctx sdk.Context, height exported.Height) (
 
 // ValidateSelfClient validates the client parameters for a client of the running chain
 // This function is only used to validate the client state the counterparty stores for this chain
+// Client must be in same epoch as the executing chain
 func (k Keeper) ValidateSelfClient(ctx sdk.Context, clientState exported.ClientState) error {
 	tmClient, ok := clientState.(*ibctmtypes.ClientState)
 	if !ok {
@@ -230,9 +232,15 @@ func (k Keeper) ValidateSelfClient(ctx sdk.Context, clientState exported.ClientS
 			ctx.ChainID(), tmClient.ChainId)
 	}
 
-	// For now, assume epoch number is zero
+	epoch := types.ParseChainID(ctx.ChainID())
-	// TODO: Retrieve epoch number from chain-id
+
-	selfHeight := types.NewHeight(0, uint64(ctx.BlockHeight()))
+	// client must be in the same epoch as executing chain
+	if tmClient.LatestHeight.EpochNumber != epoch {
+		return sdkerrors.Wrapf(types.ErrInvalidClient, "client is not in the same epoch as the chain. expected epoch: %d, got: %d",
+			tmClient.LatestHeight.EpochNumber, epoch)
+	}
+
+	selfHeight := types.NewHeight(epoch, uint64(ctx.BlockHeight()))
 	if tmClient.LatestHeight.GT(selfHeight) {
 		return sdkerrors.Wrapf(types.ErrInvalidClient, "client has LatestHeight %d greater than chain height %d",
 			tmClient.LatestHeight, ctx.BlockHeight())

x/ibc/02-client/keeper/keeper_test.go

@@ -26,7 +26,8 @@ import (
 )
 
 const (
-	testChainID = "gaiahub"
+	testChainID       = "gaiahub-0"
+	testChainIDEpoch1 = "gaiahub-1"
 
 	testClientID  = "gaiachain"
 	testClientID2 = "ethbridge"
@@ -40,6 +41,7 @@ const (
 )
 
 var testClientHeight = types.NewHeight(0, 5)
+var testClientHeightEpoch1 = types.NewHeight(1, 5)
 
 type KeeperTestSuite struct {
 	suite.Suite
@@ -83,10 +85,12 @@ func (suite *KeeperTestSuite) SetupTest() {
 	pubKey, err := suite.privVal.GetPubKey()
 	suite.Require().NoError(err)
 
+	testClientHeightMinus1 := types.NewHeight(0, height-1)
+
 	validator := tmtypes.NewValidator(pubKey, 1)
 	suite.valSet = tmtypes.NewValidatorSet([]*tmtypes.Validator{validator})
 	suite.valSetHash = suite.valSet.Hash()
-	suite.header = ibctmtypes.CreateTestHeader(testChainID, height, height-1, now2, suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
+	suite.header = ibctmtypes.CreateTestHeader(testChainID, testClientHeight, testClientHeightMinus1, now2, suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
 	suite.consensusState = ibctmtypes.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot([]byte("hash")), suite.valSetHash)
 
 	var validators stakingtypes.Validators
@@ -170,6 +174,11 @@ func (suite *KeeperTestSuite) TestValidateSelfClient() {
 			ibctmtypes.NewClientState(testChainID, ibctmtypes.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, types.NewHeight(0, testClientHeight.EpochHeight+10), commitmenttypes.GetSDKSpecs(), false, false),
 			false,
 		},
+		{
+			"invalid client epoch",
+			ibctmtypes.NewClientState(testChainIDEpoch1, ibctmtypes.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, testClientHeightEpoch1, commitmenttypes.GetSDKSpecs(), false, false),
+			false,
+		},
 		{
 			"invalid proof specs",
 			ibctmtypes.NewClientState(testChainID, ibctmtypes.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, testClientHeight, nil, false, false),
@@ -291,7 +300,9 @@ func (suite KeeperTestSuite) TestConsensusStateHelpers() {
 
 	nextState := ibctmtypes.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot([]byte("next")), suite.valSetHash)
 
-	header := ibctmtypes.CreateTestHeader(testClientID, height+5, height, suite.header.Header.Time.Add(time.Minute),
+	testClientHeightPlus5 := types.NewHeight(0, height+5)
+
+	header := ibctmtypes.CreateTestHeader(testClientID, testClientHeightPlus5, testClientHeight, suite.header.Header.Time.Add(time.Minute),
 		suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
 
 	// mock update functionality

x/ibc/02-client/types/genesis_test.go

@@ -53,7 +53,8 @@ func TestValidateGenesis(t *testing.T) {
 	val := tmtypes.NewValidator(pubKey, 10)
 	valSet := tmtypes.NewValidatorSet([]*tmtypes.Validator{val})
 
-	header := ibctmtypes.CreateTestHeader(chainID, height, height-1, now, valSet, valSet, []tmtypes.PrivValidator{privVal})
+	heightMinus1 := types.NewHeight(0, height-1)
+	header := ibctmtypes.CreateTestHeader(chainID, clientHeight, heightMinus1, now, valSet, valSet, []tmtypes.PrivValidator{privVal})
 
 	testCases := []struct {
 		name     string

x/ibc/02-client/types/height.go

@@ -2,6 +2,7 @@ package types
 
 import (
 	"fmt"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -12,6 +13,11 @@ import (
 
 var _ exported.Height = (*Height)(nil)
 
+// IsEpochFormat checks if a chainID is in the format required for parsing epochs
+// The chainID must be in the form: `{chainID}-{version}
+// 24-host may enforce stricter checks on chainID
+var IsEpochFormat = regexp.MustCompile(`^.+[^-]-{1}[1-9][0-9]*$`).MatchString
+
 // ZeroHeight is a helper function which returns an uninitialized height.
 func ZeroHeight() Height {
 	return Height{}
@@ -35,7 +41,7 @@ func (h Height) GetEpochHeight() uint64 {
 	return h.EpochHeight
 }
 
-/// Compare implements a method to compare two heights. When comparing two heights a, b
+// Compare implements a method to compare two heights. When comparing two heights a, b
 // we can call a.Compare(b) which will return
 // -1 if a < b
 // 0  if a = b
@@ -143,8 +149,42 @@ func ParseHeight(heightStr string) (Height, error) {
 	return NewHeight(epochNumber, epochHeight), nil
 }
 
-// GetSelfHeight is a utility function that returns self height given context
+// SetEpochNumber takes a chainID in valid epoch format and swaps the epoch number
-// TODO: Retrieve epoch-number from chain-id
+// in the chainID with the given epoch number.
-func GetSelfHeight(ctx sdk.Context) Height {
+func SetEpochNumber(chainID string, epoch uint64) (string, error) {
-	return NewHeight(0, uint64(ctx.BlockHeight()))
+	if !IsEpochFormat(chainID) {
+		return "", sdkerrors.Wrapf(
+			sdkerrors.ErrInvalidChainID, "chainID is not in epoch format: %s", chainID,
+		)
+	}
+
+	splitStr := strings.Split(chainID, "-")
+	// swap out epoch number with given epoch
+	splitStr[len(splitStr)-1] = strconv.Itoa(int(epoch))
+	return strings.Join(splitStr, "-"), nil
+}
+
+// ParseChainID is a utility function that returns an epoch number from the given ChainID.
+// ParseChainID attempts to parse a chain id in the format: `{chainID}-{version}`
+// and return the epochnumber as a uint64.
+// If the chainID is not in the expected format, a default epoch value of 0 is returned.
+func ParseChainID(chainID string) uint64 {
+	if !IsEpochFormat(chainID) {
+		// chainID is not in epoch format, return 0 as default
+		return 0
+	}
+	splitStr := strings.Split(chainID, "-")
+	epoch, err := strconv.ParseUint(splitStr[len(splitStr)-1], 10, 64)
+	// sanity check: error should always be nil since regex only allows numbers in last element
+	if err != nil {
+		panic(fmt.Sprintf("regex allowed non-number value as last split element for chainID: %s", chainID))
+	}
+	return epoch
+}
+
+// GetSelfHeight is a utility function that returns self height given context
+// Epoch number is retrieved from ctx.ChainID()
+func GetSelfHeight(ctx sdk.Context) Height {
+	epoch := ParseChainID(ctx.ChainID())
+	return NewHeight(epoch, uint64(ctx.BlockHeight()))
 }

x/ibc/02-client/types/height_test.go

@@ -93,3 +93,56 @@ func (suite *TypesTestSuite) TestMustParseHeight() {
 		types.MustParseHeight("0-0")
 	})
 }
+
+func TestParseChainID(t *testing.T) {
+	cases := []struct {
+		chainID   string
+		epoch     uint64
+		formatted bool
+	}{
+		{"gaiamainnet-3", 3, true},
+		{"gaia-mainnet-40", 40, true},
+		{"gaiamainnet-3-39", 39, true},
+		{"gaiamainnet--", 0, false},
+		{"gaiamainnet-03", 0, false},
+		{"gaiamainnet--4", 0, false},
+		{"gaiamainnet-3.4", 0, false},
+		{"gaiamainnet", 0, false},
+	}
+
+	for i, tc := range cases {
+		require.Equal(t, tc.formatted, types.IsEpochFormat(tc.chainID), "case %d does not match expected format", i)
+
+		epoch := types.ParseChainID(tc.chainID)
+		require.Equal(t, tc.epoch, epoch, "case %d returns incorrect epoch", i)
+	}
+
+}
+
+func TestSetEpochNumber(t *testing.T) {
+	// Test SetEpochNumber
+	chainID, err := types.SetEpochNumber("gaiamainnet", 3)
+	require.Error(t, err, "invalid epoch format passed SetEpochNumber")
+	require.Equal(t, "", chainID, "invalid epoch format returned non-empty string on SetEpochNumber")
+	chainID = "gaiamainnet-3"
+
+	chainID, err = types.SetEpochNumber(chainID, 4)
+	require.NoError(t, err, "valid epoch format failed SetEpochNumber")
+	require.Equal(t, "gaiamainnet-4", chainID, "valid epoch format returned incorrect string on SetEpochNumber")
+}
+
+func (suite *TypesTestSuite) TestSelfHeight() {
+	ctx := suite.chainA.GetContext()
+
+	// Test default epoch
+	ctx = ctx.WithChainID("gaiamainnet")
+	ctx = ctx.WithBlockHeight(10)
+	height := types.GetSelfHeight(ctx)
+	suite.Require().Equal(types.NewHeight(0, 10), height, "default self height failed")
+
+	// Test successful epoch format
+	ctx = ctx.WithChainID("gaiamainnet-3")
+	ctx = ctx.WithBlockHeight(18)
+	height = types.GetSelfHeight(ctx)
+	suite.Require().Equal(types.NewHeight(3, 18), height, "valid self height failed")
+}

x/ibc/02-client/types/msgs_test.go

@@ -354,8 +354,10 @@ func (suite *TypesTestSuite) TestMarshalMsgSubmitMisbehaviour() {
 		},
 		{
 			"tendermint client", func() {
-				header1 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, suite.chainA.CurrentHeader.Height, suite.chainA.CurrentHeader.Height-1, suite.chainA.CurrentHeader.Time, suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				height := types.NewHeight(0, uint64(suite.chainA.CurrentHeader.Height))
-				header2 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, suite.chainA.CurrentHeader.Height, suite.chainA.CurrentHeader.Height-1, suite.chainA.CurrentHeader.Time.Add(time.Minute), suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				heightMinus1 := types.NewHeight(0, uint64(suite.chainA.CurrentHeader.Height)-1)
+				header1 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, height, heightMinus1, suite.chainA.CurrentHeader.Time, suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				header2 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, height, heightMinus1, suite.chainA.CurrentHeader.Time.Add(time.Minute), suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
 
 				misbehaviour := ibctmtypes.NewMisbehaviour("tendermint", suite.chainA.ChainID, header1, header2)
 				msg, err = types.NewMsgSubmitMisbehaviour("tendermint", misbehaviour, suite.chainA.SenderAccount.GetAddress())
@@ -410,8 +412,10 @@ func (suite *TypesTestSuite) TestMsgSubmitMisbehaviour_ValidateBasic() {
 		{
 			"valid - tendermint misbehaviour",
 			func() {
-				header1 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, suite.chainA.CurrentHeader.Height, suite.chainA.CurrentHeader.Height-1, suite.chainA.CurrentHeader.Time, suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				height := types.NewHeight(0, uint64(suite.chainA.CurrentHeader.Height))
-				header2 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, suite.chainA.CurrentHeader.Height, suite.chainA.CurrentHeader.Height-1, suite.chainA.CurrentHeader.Time.Add(time.Minute), suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				heightMinus1 := types.NewHeight(0, uint64(suite.chainA.CurrentHeader.Height)-1)
+				header1 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, height, heightMinus1, suite.chainA.CurrentHeader.Time, suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
+				header2 := ibctmtypes.CreateTestHeader(suite.chainA.ChainID, height, heightMinus1, suite.chainA.CurrentHeader.Time.Add(time.Minute), suite.chainA.Vals, suite.chainA.Vals, suite.chainA.Signers)
 
 				misbehaviour := ibctmtypes.NewMisbehaviour("tendermint", suite.chainA.ChainID, header1, header2)
 				msg, err = types.NewMsgSubmitMisbehaviour("tendermint", misbehaviour, suite.chainA.SenderAccount.GetAddress())

x/ibc/04-channel/client/utils/utils.go

@@ -51,7 +51,6 @@ func queryPacketCommitmentABCI(
 		return nil, sdkerrors.Wrapf(types.ErrPacketCommitmentNotFound, "portID (%s), channelID (%s), sequence (%d)", portID, channelID, sequence)
 	}
 
-	// TODO: retrieve epoch number from chain-id
 	return types.NewQueryPacketCommitmentResponse(portID, channelID, sequence, value, proofBz, proofHeight), nil
 }
 
@@ -230,6 +229,5 @@ func queryNextSequenceRecvABCI(clientCtx client.Context, portID, channelID strin
 
 	sequence := binary.BigEndian.Uint64(value)
 
-	// TODO: retrieve epoch number from chain-id
 	return types.NewQueryNextSequenceReceiveResponse(portID, channelID, sequence, proofBz, proofHeight), nil
 }

x/ibc/07-tendermint/types/header.go

@@ -30,16 +30,12 @@ func (h Header) ConsensusState() *ConsensusState {
 
 // GetHeight returns the current height. It returns 0 if the tendermint
 // header is nil.
-//
-// TODO: return clienttypes.Height once interface changes
 func (h Header) GetHeight() exported.Height {
 	if h.Header == nil {
 		return clienttypes.ZeroHeight()
 	}
-
+	epoch := clienttypes.ParseChainID(h.Header.ChainID)
-	// Enforce clienttypes.Height to use 0 epoch number
+	return clienttypes.NewHeight(epoch, uint64(h.Header.Height))
-	// TODO: Retrieve epoch number from chain-id
-	return clienttypes.NewHeight(0, uint64(h.Header.Height))
 }
 
 // GetTime returns the current block timestamp. It returns a zero time if

x/ibc/07-tendermint/types/misbehaviour_handle.go

@@ -62,7 +62,7 @@ func (cs ClientState) CheckMisbehaviourAndUpdateState(
 		infractionHeight := tmMisbehaviour.GetHeight().GetEpochHeight()
 		ageBlocks = int64(cs.LatestHeight.EpochHeight - infractionHeight)
 	} else {
-		// if the misbehaviour is from a previous epoch, then the epoch-height
+		// if the misbehaviour is from a different epoch, then the epoch-height
 		// of misbehaviour has no correlation with the current epoch-height
 		// so we disable the block check by setting ageBlocks to 0 and only
 		// rely on the time expiry check with ageDuration
@@ -136,15 +136,22 @@ func checkMisbehaviourHeader(
 	if currentTimestamp.Sub(consState.Timestamp) >= clientState.UnbondingPeriod {
 		return sdkerrors.Wrapf(
 			ErrUnbondingPeriodExpired,
-			"current timestamp minus the latest consensus state timestamp is greater than or equal to the unbonding period (%s >= %s)",
+			"current timestamp minus the latest consensus state timestamp is greater than or equal to the unbonding period (%d >= %d)",
 			currentTimestamp.Sub(consState.Timestamp), clientState.UnbondingPeriod,
 		)
 	}
 
+	chainID := clientState.GetChainID()
+	// If chainID is in epoch format, then set epoch number of chainID with the epoch number
+	// of the misbehaviour header
+	if clienttypes.IsEpochFormat(chainID) {
+		chainID, _ = clienttypes.SetEpochNumber(chainID, header.GetHeight().GetEpochNumber())
+	}
+
 	// - ValidatorSet must have 2/3 similarity with trusted FromValidatorSet
 	// - ValidatorSets on both headers are valid given the last trusted ValidatorSet
 	if err := tmTrustedValset.VerifyCommitLightTrusting(
-		clientState.GetChainID(), tmCommit, clientState.TrustLevel.ToTendermint(),
+		chainID, tmCommit, clientState.TrustLevel.ToTendermint(),
 	); err != nil {
 		return sdkerrors.Wrapf(clienttypes.ErrInvalidMisbehaviour, "validator set in header has too much change from trusted validator set: %v", err)
 	}

x/ibc/07-tendermint/types/misbehaviour_handle_test.go

@@ -58,8 +58,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -74,8 +74,88 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			heightMinus1,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				ChainId:  chainID,
+				ClientId: chainID,
+			},
+			suite.now,
+			true,
+		},
+		{
+			"valid misbehaviour with different trusted heights",
+			types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
+			heightMinus1,
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			heightMinus3,
+			&types.Misbehaviour{
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus3, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				ChainId:  chainID,
+				ClientId: chainID,
+			},
+			suite.now,
+			true,
+		},
+		{
+			"valid misbehaviour at a previous epoch",
+			types.NewClientState(chainIDEpoch1, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, clienttypes.NewHeight(1, 1), commitmenttypes.GetSDKSpecs(), false, false),
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
+			heightMinus1,
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			heightMinus3,
+			&types.Misbehaviour{
+				Header1:  types.CreateTestHeader(chainIDEpoch0, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainIDEpoch0, height, heightMinus3, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				ChainId:  chainIDEpoch0,
+				ClientId: chainID,
+			},
+			suite.now,
+			true,
+		},
+		{
+			"valid misbehaviour at a future epoch",
+			types.NewClientState(chainIDEpoch0, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
+			heightMinus1,
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			heightMinus3,
+			&types.Misbehaviour{
+				Header1:  types.CreateTestHeader(chainIDEpoch0, clienttypes.NewHeight(1, 3), heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainIDEpoch0, clienttypes.NewHeight(1, 3), heightMinus3, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				ChainId:  chainIDEpoch0,
+				ClientId: chainID,
+			},
+			suite.now,
+			true,
+		},
+		{
+			"valid misbehaviour with trusted heights at a previous epoch",
+			types.NewClientState(chainIDEpoch1, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, clienttypes.NewHeight(1, 1), commitmenttypes.GetSDKSpecs(), false, false),
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
+			heightMinus1,
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			heightMinus3,
+			&types.Misbehaviour{
+				Header1:  types.CreateTestHeader(chainIDEpoch1, clienttypes.NewHeight(1, 1), heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainIDEpoch1, clienttypes.NewHeight(1, 1), heightMinus3, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				ChainId:  chainIDEpoch1,
+				ClientId: chainID,
+			},
+			suite.now,
+			true,
+		},
+		{
+			"consensus state's valset hash different from misbehaviour should still pass",
+			types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			height,
+			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
+			height,
+			&types.Misbehaviour{
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, suite.valSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -90,46 +170,14 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader("ethermint", int64(height.EpochHeight), int64(height.EpochHeight), suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader("ethermint", height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader("ethermint", int64(height.EpochHeight), int64(height.EpochHeight), suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader("ethermint", height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  "ethermint",
 				ClientId: chainID,
 			},
 			suite.now,
 			false,
 		},
-		{
-			"valid misbehavior misbehaviour with different trusted heights",
-			types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
-			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
-			heightMinus1,
-			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
-			heightMinus3,
-			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-3, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
-				ChainId:  chainID,
-				ClientId: chainID,
-			},
-			suite.now,
-			true,
-		},
-		{
-			"consensus state's valset hash different from misbehaviour should still pass",
-			types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
-			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
-			height,
-			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
-			height,
-			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, suite.valSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
-				ChainId:  chainID,
-				ClientId: chainID,
-			},
-			suite.now,
-			true,
-		},
 		{
 			"invalid misbehavior misbehaviour with trusted height different from trusted consensus state",
 			types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false),
@@ -138,8 +186,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
 			heightMinus3,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -154,8 +202,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), suite.valsHash),
 			heightMinus3,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-3, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus3, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -170,8 +218,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -186,8 +234,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -213,8 +261,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -229,8 +277,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -245,8 +293,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -261,8 +309,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -277,8 +325,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, suite.valSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, suite.valSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, suite.valSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -293,8 +341,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, altValSet, bothValSet, altSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, altValSet, bothValSet, altSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), bothValSet, bothValSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -309,8 +357,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, bothValSet, bothValSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, bothValSet, bothValSet, bothSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), altValSet, bothValSet, altSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), altValSet, bothValSet, altSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},
@@ -325,8 +373,8 @@ func (suite *TendermintTestSuite) TestCheckMisbehaviourAndUpdateState() {
 			types.NewConsensusState(suite.now, commitmenttypes.NewMerkleRoot(tmhash.Sum([]byte("app_hash"))), bothValsHash),
 			height,
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now, altValSet, bothValSet, altSigners),
+				Header1:  types.CreateTestHeader(chainID, height, height, suite.now, altValSet, bothValSet, altSigners),
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight, suite.now.Add(time.Minute), altValSet, bothValSet, altSigners),
+				Header2:  types.CreateTestHeader(chainID, height, height, suite.now.Add(time.Minute), altValSet, bothValSet, altSigners),
 				ChainId:  chainID,
 				ClientId: chainID,
 			},

x/ibc/07-tendermint/types/misbehaviour_test.go

@@ -7,6 +7,7 @@ import (
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 	tmtypes "github.com/tendermint/tendermint/types"
 
+	clienttypes "github.com/cosmos/cosmos-sdk/x/ibc/02-client/types"
 	"github.com/cosmos/cosmos-sdk/x/ibc/07-tendermint/types"
 	"github.com/cosmos/cosmos-sdk/x/ibc/exported"
 	ibctestingmock "github.com/cosmos/cosmos-sdk/x/ibc/testing/mock"
@@ -14,11 +15,11 @@ import (
 
 func (suite *TendermintTestSuite) TestMisbehaviour() {
 	signers := []tmtypes.PrivValidator{suite.privVal}
-	epochHeight := int64(height.EpochHeight)
+	heightMinus1 := clienttypes.NewHeight(0, height.EpochHeight-1)
 
 	misbehaviour := &types.Misbehaviour{
 		Header1:  suite.header,
-		Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, suite.valSet, suite.valSet, signers),
+		Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, suite.valSet, suite.valSet, signers),
 		ChainId:  chainID,
 		ClientId: clientID,
 	}
@@ -50,6 +51,8 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 
 	altSigners := []tmtypes.PrivValidator{altPrivVal}
 
+	heightMinus1 := clienttypes.NewHeight(0, height.EpochHeight-1)
+
 	testCases := []struct {
 		name                 string
 		misbehaviour         *types.Misbehaviour
@@ -60,7 +63,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"valid misbehaviour",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -83,7 +86,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"valid misbehaviour with different trusted headers",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-3, suite.now.Add(time.Minute), suite.valSet, bothValSet, signers),
+				Header2:  types.CreateTestHeader(chainID, height, clienttypes.NewHeight(0, height.EpochHeight-3), suite.now.Add(time.Minute), suite.valSet, bothValSet, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -93,7 +96,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 		{
 			"trusted height is 0 in Header1",
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, 0, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
+				Header1:  types.CreateTestHeader(chainID, height, clienttypes.ZeroHeight(), suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
 				Header2:  suite.header,
 				ChainId:  chainID,
 				ClientId: clientID,
@@ -105,7 +108,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"trusted height is 0 in Header2",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, 0, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader(chainID, height, clienttypes.ZeroHeight(), suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -115,7 +118,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 		{
 			"trusted valset is nil in Header1",
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now.Add(time.Minute), suite.valSet, nil, signers),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), suite.valSet, nil, signers),
 				Header2:  suite.header,
 				ChainId:  chainID,
 				ClientId: clientID,
@@ -127,7 +130,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"trusted valset is nil in Header2",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now.Add(time.Minute), suite.valSet, nil, signers),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), suite.valSet, nil, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -138,7 +141,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"invalid client ID ",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, suite.valSet, suite.valSet, signers),
 				ChainId:  chainID,
 				ClientId: "GAIA",
 			},
@@ -149,7 +152,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"wrong chainID on header1",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader("ethermint", epochHeight, epochHeight-1, suite.now, suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader("ethermint", height, heightMinus1, suite.now, suite.valSet, suite.valSet, signers),
 				ChainId:  "ethermint",
 				ClientId: clientID,
 			},
@@ -160,7 +163,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"wrong chainID on header2",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader("ethermint", epochHeight, epochHeight-1, suite.now, suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader("ethermint", height, heightMinus1, suite.now, suite.valSet, suite.valSet, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -171,7 +174,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"wrong chainID in misbehaviour",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, int64(height.EpochHeight), int64(height.EpochHeight-1), suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers),
 				ChainId:  "ethermint",
 				ClientId: clientID,
 			},
@@ -182,7 +185,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"mismatched heights",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, 6, 4, suite.now, suite.valSet, suite.valSet, signers),
+				Header2:  types.CreateTestHeader(chainID, clienttypes.NewHeight(0, 6), clienttypes.NewHeight(0, 4), suite.now, suite.valSet, suite.valSet, signers),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -203,7 +206,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 		{
 			"header 1 doesn't have 2/3 majority",
 			&types.Misbehaviour{
-				Header1:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, suite.valSet, bothSigners),
+				Header1:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, suite.valSet, bothSigners),
 				Header2:  suite.header,
 				ChainId:  chainID,
 				ClientId: clientID,
@@ -226,7 +229,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"header 2 doesn't have 2/3 majority",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, suite.valSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, suite.valSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},
@@ -248,7 +251,7 @@ func (suite *TendermintTestSuite) TestMisbehaviourValidateBasic() {
 			"validators sign off on wrong commit",
 			&types.Misbehaviour{
 				Header1:  suite.header,
-				Header2:  types.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, bothValSet, suite.valSet, bothSigners),
+				Header2:  types.CreateTestHeader(chainID, height, heightMinus1, suite.now, bothValSet, suite.valSet, bothSigners),
 				ChainId:  chainID,
 				ClientId: clientID,
 			},

x/ibc/07-tendermint/types/tendermint_test.go

@@ -20,6 +20,8 @@ import (
 
 const (
 	chainID                      = "gaia"
+	chainIDEpoch0                = "gaia-epoch-0"
+	chainIDEpoch1                = "gaia-epoch-1"
 	clientID                     = "gaiamainnet"
 	trustingPeriod time.Duration = time.Hour * 24 * 7 * 2
 	ubdPeriod      time.Duration = time.Hour * 24 * 7 * 3
@@ -72,12 +74,12 @@ func (suite *TendermintTestSuite) SetupTest() {
 	pubKey, err := suite.privVal.GetPubKey()
 	suite.Require().NoError(err)
 
-	epochHeight := int64(height.EpochHeight)
+	heightMinus1 := clienttypes.NewHeight(0, height.EpochHeight-1)
 
 	val := tmtypes.NewValidator(pubKey, 10)
 	suite.valSet = tmtypes.NewValidatorSet([]*tmtypes.Validator{val})
 	suite.valsHash = suite.valSet.Hash()
-	suite.header = ibctmtypes.CreateTestHeader(chainID, epochHeight, epochHeight-1, suite.now, suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
+	suite.header = ibctmtypes.CreateTestHeader(chainID, height, heightMinus1, suite.now, suite.valSet, suite.valSet, []tmtypes.PrivValidator{suite.privVal})
 	suite.ctx = app.BaseApp.NewContext(checkTx, tmproto.Header{Height: 1, Time: suite.now})
 }
 

x/ibc/07-tendermint/types/test_utils.go

@@ -24,16 +24,17 @@ func MakeBlockID(hash []byte, partSetSize uint32, partSetHash []byte) tmtypes.Bl
 }
 
 // CreateTestHeader creates a mock header for testing only.
-func CreateTestHeader(chainID string, height, trustedHeight int64, timestamp time.Time, tmValSet, tmTrustedVals *tmtypes.ValidatorSet, signers []tmtypes.PrivValidator) *Header {
+func CreateTestHeader(chainID string, height, trustedHeight clienttypes.Height, timestamp time.Time, tmValSet, tmTrustedVals *tmtypes.ValidatorSet, signers []tmtypes.PrivValidator) *Header {
 	var (
 		valSet      *tmproto.ValidatorSet
 		trustedVals *tmproto.ValidatorSet
 	)
 	vsetHash := tmValSet.Hash()
+	blockHeight := int64(height.EpochHeight)
 	tmHeader := tmtypes.Header{
 		Version:            version.Consensus{Block: 2, App: 2},
 		ChainID:            chainID,
-		Height:             height,
+		Height:             blockHeight,
 		Time:               timestamp,
 		LastBlockID:        MakeBlockID(make([]byte, tmhash.Size), 10_000, make([]byte, tmhash.Size)),
 		LastCommitHash:     tmhash.Sum([]byte("last_commit_hash")),
@@ -49,8 +50,8 @@ func CreateTestHeader(chainID string, height, trustedHeight int64, timestamp tim
 
 	hhash := tmHeader.Hash()
 	blockID := MakeBlockID(hhash, 3, tmhash.Sum([]byte("part_set")))
-	voteSet := tmtypes.NewVoteSet(chainID, height, 1, tmproto.PrecommitType, tmValSet)
+	voteSet := tmtypes.NewVoteSet(chainID, blockHeight, 1, tmproto.PrecommitType, tmValSet)
-	commit, err := tmtypes.MakeCommit(blockID, height, 1, voteSet, signers, timestamp)
+	commit, err := tmtypes.MakeCommit(blockID, blockHeight, 1, voteSet, signers, timestamp)
 	if err != nil {
 		panic(err)
 	}
@@ -77,7 +78,7 @@ func CreateTestHeader(chainID string, height, trustedHeight int64, timestamp tim
 	return &Header{
 		SignedHeader:      &signedHeader,
 		ValidatorSet:      valSet,
-		TrustedHeight:     clienttypes.NewHeight(0, uint64(trustedHeight)),
+		TrustedHeight:     trustedHeight,
 		TrustedValidators: trustedVals,
 	}
 }

x/ibc/07-tendermint/types/update.go

@@ -21,7 +21,8 @@ import (
 // It returns an error if:
 // - the client or header provided are not parseable to tendermint types
 // - the header is invalid
-// - header height is less than or equal to the consensus state height
+// - header height is less than or equal to the trusted header height
+// - header epoch is not equal to trusted header epoch
 // - header valset commit verification fails
 // - header timestamp is past the trusting period in relation to the consensus state
 // - header timestamp is less than or equal to the consensus state timestamp
@@ -32,6 +33,8 @@ import (
 // If we are updating to a past height, a consensus state is created for that height to be persisted in client store
 // If we are updating to a future height, the consensus state is created and the client state is updated to reflect
 // the new latest height
+// UpdateClient must only be used to update within a single epoch, thus header epoch number and trusted height's epoch
+// number must be the same. To update to a new epoch, use a separate upgrade path
 // Tendermint client validity checking uses the bisection algorithm described
 // in the [Tendermint spec](https://github.com/tendermint/spec/blob/master/spec/consensus/light-client.md).
 func (cs ClientState) CheckHeaderAndUpdateState(
@@ -91,6 +94,16 @@ func checkValidity(
 		return err
 	}
 
+	// UpdateClient only accepts updates with a header at the same epoch
+	// as the trusted consensus state
+	if header.GetHeight().GetEpochNumber() != header.TrustedHeight.EpochNumber {
+		return sdkerrors.Wrapf(
+			ErrInvalidHeaderHeight,
+			"header height epoch %d does not match trusted header epoch %d",
+			header.GetHeight().GetEpochNumber(), header.TrustedHeight.EpochNumber,
+		)
+	}
+
 	tmTrustedValidators, err := tmtypes.ValidatorSetFromProto(header.TrustedValidators)
 	if err != nil {
 		return sdkerrors.Wrap(err, "trusted validator set in not tendermint validator set type")
@@ -110,7 +123,7 @@ func checkValidity(
 	if header.GetHeight().LTE(header.TrustedHeight) {
 		return sdkerrors.Wrapf(
 			clienttypes.ErrInvalidHeader,
-			"header height ≤ consensus state height (%d ≤ %d)", header.GetHeight(), header.TrustedHeight,
+			"header height ≤ consensus state height (%s ≤ %s)", header.GetHeight(), header.TrustedHeight,
 		)
 	}
 
@@ -125,13 +138,24 @@ func checkValidity(
 		Header: &trustedHeader,
 	}
 
+	chainID := clientState.GetChainID()
+	// If chainID is in epoch format, then set epoch number of chainID with the epoch number
+	// of the header we are verifying
+	// This is useful if the update is at a previous epoch rather than an update to the latest epoch
+	// of the client.
+	// The chainID must be set correctly for the previous epoch before attempting verification.
+	// Updates for previous epochs are not supported if the chainID is not in epoch format.
+	if clienttypes.IsEpochFormat(chainID) {
+		chainID, _ = clienttypes.SetEpochNumber(chainID, header.GetHeight().GetEpochNumber())
+	}
+
 	// Verify next header with the passed-in trustedVals
 	// - asserts trusting period not passed
 	// - assert header timestamp is not past the trusting period
 	// - assert header timestamp is past latest stored consensus state timestamp
 	// - assert that a TrustLevel proportion of TrustedValidators signed new Commit
 	err = light.Verify(
-		clientState.GetChainID(), &signedHeader,
+		chainID, &signedHeader,
 		tmTrustedValidators, tmSignedHeader, tmValidatorSet,
 		clientState.TrustingPeriod, currentTimestamp, clientState.MaxClockDrift, clientState.TrustLevel.ToTendermint(),
 	)

x/ibc/07-tendermint/types/update_test.go

@@ -26,6 +26,10 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 	suite.Require().NoError(err)
 
 	epochHeight := int64(height.EpochHeight)
+
+	// create modified heights to use for test-cases
+	heightPlus1 := clienttypes.NewHeight(height.EpochNumber, height.EpochHeight+1)
+	heightMinus1 := clienttypes.NewHeight(height.EpochNumber, height.EpochHeight-1)
 	heightMinus3 := clienttypes.NewHeight(height.EpochNumber, height.EpochHeight-3)
 	heightPlus5 := clienttypes.NewHeight(height.EpochNumber, height.EpochHeight+5)
 
@@ -54,7 +58,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, suite.valSet, suite.valSet, signers)
 				currentTime = suite.now
 			},
 			expPass: true,
@@ -64,7 +68,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+5, epochHeight, suite.headerTime, bothValSet, suite.valSet, bothSigners)
+				newHeader = types.CreateTestHeader(chainID, heightPlus5, height, suite.headerTime, bothValSet, suite.valSet, bothSigners)
 				currentTime = suite.now
 			},
 			expPass: true,
@@ -74,7 +78,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), bothValSet.Hash())
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, bothValSet, bothValSet, bothSigners)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, bothValSet, bothValSet, bothSigners)
 				currentTime = suite.now
 			},
 			expPass: true,
@@ -85,7 +89,17 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
 				consStateHeight = heightMinus3
-				newHeader = types.CreateTestHeader(chainID, epochHeight-1, epochHeight-3, suite.headerTime, bothValSet, suite.valSet, bothSigners)
+				newHeader = types.CreateTestHeader(chainID, heightMinus1, heightMinus3, suite.headerTime, bothValSet, suite.valSet, bothSigners)
+				currentTime = suite.now
+			},
+			expPass: true,
+		},
+		{
+			name: "successful update for a previous epoch",
+			setup: func() {
+				clientState = types.NewClientState(chainIDEpoch1, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
+				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
+				newHeader = types.CreateTestHeader(chainIDEpoch0, height, heightMinus3, suite.headerTime, bothValSet, suite.valSet, bothSigners)
 				currentTime = suite.now
 			},
 			expPass: true,
@@ -95,7 +109,27 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader("ethermint", int64(height.EpochHeight+1), int64(height.EpochHeight), suite.headerTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader("ethermint", heightPlus1, height, suite.headerTime, suite.valSet, suite.valSet, signers)
+				currentTime = suite.now
+			},
+			expPass: false,
+		},
+		{
+			name: "unsuccessful update to a future epoch",
+			setup: func() {
+				clientState = types.NewClientState(chainIDEpoch0, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
+				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
+				newHeader = types.CreateTestHeader(chainIDEpoch1, clienttypes.NewHeight(1, 1), height, suite.headerTime, suite.valSet, suite.valSet, signers)
+				currentTime = suite.now
+			},
+			expPass: false,
+		},
+		{
+			name: "unsuccessful update: header height epoch and trusted height epoch mismatch",
+			setup: func() {
+				clientState = types.NewClientState(chainIDEpoch1, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, clienttypes.NewHeight(1, 1), commitmenttypes.GetSDKSpecs(), false, false)
+				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
+				newHeader = types.CreateTestHeader(chainIDEpoch1, clienttypes.NewHeight(1, 3), height, suite.headerTime, suite.valSet, suite.valSet, signers)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -105,7 +139,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, bothValSet, suite.valSet, bothSigners)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, bothValSet, suite.valSet, bothSigners)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -115,7 +149,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), bothValSet.Hash())
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, suite.valSet, bothValSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, suite.valSet, bothValSet, signers)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -125,7 +159,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+5, epochHeight, suite.headerTime, altValSet, suite.valSet, altSigners)
+				newHeader = types.CreateTestHeader(chainID, heightPlus5, height, suite.headerTime, altValSet, suite.valSet, altSigners)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -135,7 +169,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+5, epochHeight, suite.headerTime, bothValSet, bothValSet, bothSigners)
+				newHeader = types.CreateTestHeader(chainID, heightPlus5, height, suite.headerTime, bothValSet, bothValSet, bothSigners)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -145,7 +179,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, suite.valSet, suite.valSet, signers)
 				// make current time pass trusting period from last timestamp on clientstate
 				currentTime = suite.now.Add(trustingPeriod)
 			},
@@ -156,7 +190,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.now.Add(time.Minute), suite.valSet, suite.valSet, signers)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -166,7 +200,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.clientTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.clientTime, suite.valSet, suite.valSet, signers)
 				currentTime = suite.now
 			},
 			expPass: false,
@@ -176,7 +210,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 			setup: func() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, height, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
-				newHeader = types.CreateTestHeader(chainID, epochHeight+1, epochHeight, suite.headerTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightPlus1, height, suite.headerTime, suite.valSet, suite.valSet, signers)
 				// cause new header to fail validatebasic by changing commit height to mismatch header height
 				newHeader.SignedHeader.Commit.Height = epochHeight - 1
 				currentTime = suite.now
@@ -189,7 +223,7 @@ func (suite *TendermintTestSuite) TestCheckHeaderAndUpdateState() {
 				clientState = types.NewClientState(chainID, types.DefaultTrustLevel, trustingPeriod, ubdPeriod, maxClockDrift, heightPlus5, commitmenttypes.GetSDKSpecs(), false, false)
 				consensusState = types.NewConsensusState(suite.clientTime, commitmenttypes.NewMerkleRoot(suite.header.Header.GetAppHash()), suite.valsHash)
 				// Make new header at height less than latest client state
-				newHeader = types.CreateTestHeader(chainID, epochHeight-1, epochHeight, suite.headerTime, suite.valSet, suite.valSet, signers)
+				newHeader = types.CreateTestHeader(chainID, heightMinus1, height, suite.headerTime, suite.valSet, suite.valSet, signers)
 				currentTime = suite.now
 			},
 			expPass: false,

x/ibc/09-localhost/types/client_state.go

@@ -75,9 +75,8 @@ func (cs *ClientState) CheckHeaderAndUpdateState(
 ) (exported.ClientState, exported.ConsensusState, error) {
 	// use the chain ID from context since the localhost client is from the running chain (i.e self).
 	cs.ChainId = ctx.ChainID()
-	// Hardcode 0 for epoch number for now
+	epoch := clienttypes.ParseChainID(cs.ChainId)
-	// TODO: Retrieve epoch number from chain-id
+	cs.Height = clienttypes.NewHeight(epoch, uint64(ctx.BlockHeight()))
-	cs.Height = clienttypes.NewHeight(0, uint64(ctx.BlockHeight()))
 	return cs, nil, nil
 }
 

x/ibc/client/query.go

@@ -40,6 +40,6 @@ func QueryTendermintProof(clientCtx client.Context, key []byte) ([]byte, []byte,
 		return nil, nil, clienttypes.Height{}, err
 	}
 
-	// TODO: retrieve epoch number from chain-id
+	epoch := clienttypes.ParseChainID(clientCtx.ChainID)
-	return res.Value, proofBz, clienttypes.NewHeight(0, uint64(res.Height)+1), nil
+	return res.Value, proofBz, clienttypes.NewHeight(epoch, uint64(res.Height)+1), nil
 }

x/ibc/ibc_test.go

@@ -63,7 +63,9 @@ func (suite *IBCTestSuite) SetupTest() {
 	val := tmtypes.NewValidator(pubKey, 10)
 	valSet := tmtypes.NewValidatorSet([]*tmtypes.Validator{val})
 
-	suite.header = ibctmtypes.CreateTestHeader(chainID, height, height-1, now, valSet, valSet, []tmtypes.PrivValidator{privVal})
+	clientHeightMinus1 := clienttypes.NewHeight(0, height-1)
+
+	suite.header = ibctmtypes.CreateTestHeader(chainID, clientHeight, clientHeightMinus1, now, valSet, valSet, []tmtypes.PrivValidator{privVal})
 
 	suite.ctx = suite.app.BaseApp.NewContext(isCheckTx, tmproto.Header{})
 }

x/ibc/spec/01_concepts.md

@@ -38,7 +38,13 @@ given by the chain's chainID, and the epoch height given by the Tendermint block
 and resets its block-height, it is responsible for updating its chain-id to increment the epoch number.
 IBC Tendermint clients then verifies the epoch number against their `ChainId` and treat the `EpochHeight` as the Tendermint block-height.
 
-TODO: Explain how to structure chain-id to make epoch-number parsable
+Tendermint chains wishing to use epochs to maintain persistent IBC connections even across height-resetting upgrades must format their chain-ids
+in the following manner: `{chainID}-{version}`. On any height-resetting upgrade, the chainID **MUST** be updated with a higher epoch number
+than the previous value.
+
+Ex:
+Before upgrade ChainID: `gaiamainnet-3`
+After upgrade ChainID: `gaiamainnet-4`
 
 Clients that do not require epochs, such as the solo-machine client, simply hardcode `0` into the epoch number whenever they 
 need to return an IBC height when implementing IBC interfaces and use the `EpochHeight` exclusively.

x/ibc/testing/chain.go

@@ -181,10 +181,12 @@ func (chain *TestChain) QueryProof(key []byte) ([]byte, clienttypes.Height) {
 	proof, err := chain.App.AppCodec().MarshalBinaryBare(&merkleProof)
 	require.NoError(chain.t, err)
 
+	epoch := clienttypes.ParseChainID(chain.ChainID)
+
 	// proof height + 1 is returned as the proof created corresponds to the height the proof
 	// was created in the IAVL tree. Tendermint and subsequently the clients that rely on it
 	// have heights 1 above the IAVL tree. Thus we return proof height + 1
-	return proof, clienttypes.NewHeight(0, uint64(res.Height)+1)
+	return proof, clienttypes.NewHeight(epoch, uint64(res.Height)+1)
 }
 
 // QueryClientStateProof performs and abci query for a client state