imp(release/v7.5.x): emit host disabled event (#6147)

* imp: emit host disabled event

* add changelog

CHANGELOG.md

@@ -44,6 +44,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (apps/27-interchain-accounts) [\#6147](https://github.com/cosmos/ibc-go/pull/6147) Emit an event signalling that the host submodule is disabled.
+
 ### Features
 
 ### Bug Fixes

modules/apps/27-interchain-accounts/host/ibc_module.go

@@ -106,6 +106,7 @@ func (im IBCModule) OnRecvPacket(
 	_ sdk.AccAddress,
 ) ibcexported.Acknowledgement {
 	if !im.keeper.IsHostEnabled(ctx) {
+		keeper.EmitHostDisabledEvent(ctx, packet)
 		return channeltypes.NewErrorAcknowledgement(types.ErrHostSubModuleDisabled)
 	}
 

modules/apps/27-interchain-accounts/host/keeper/events.go

@@ -5,7 +5,9 @@ import (
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
+	"github.com/cosmos/ibc-go/v7/modules/apps/27-interchain-accounts/host/types"
 	icatypes "github.com/cosmos/ibc-go/v7/modules/apps/27-interchain-accounts/types"
+	channeltypes "github.com/cosmos/ibc-go/v7/modules/core/04-channel/types"
 	"github.com/cosmos/ibc-go/v7/modules/core/exported"
 )
 
@@ -29,3 +31,16 @@ func EmitAcknowledgementEvent(ctx sdk.Context, packet exported.PacketI, ack expo
 		),
 	)
 }
+
+// EmitHostDisabledEvent emits an event signalling that the host submodule is disabled.
+func EmitHostDisabledEvent(ctx sdk.Context, packet channeltypes.Packet) {
+	ctx.EventManager().EmitEvent(
+		sdk.NewEvent(
+			icatypes.EventTypePacket,
+			sdk.NewAttribute(sdk.AttributeKeyModule, icatypes.ModuleName),
+			sdk.NewAttribute(icatypes.AttributeKeyHostChannelID, packet.GetDestChannel()),
+			sdk.NewAttribute(icatypes.AttributeKeyAckError, types.ErrHostSubModuleDisabled.Error()),
+			sdk.NewAttribute(icatypes.AttributeKeyAckSuccess, "false"),
+		),
+	)
+}