multi: handle trade suspension messages.

This adds the suspension handler to the client core.

client/core/core.go

@@ -60,6 +60,9 @@ type dexConnection struct {
 
 	tradeMtx sync.RWMutex
 	trades   map[order.OrderID]*trackedTrade
+
+	suspensionEpochMtx sync.RWMutex
+	suspensionEpoch    uint64
 }
 
 // refreshMarkets rebuilds, saves, and returns the market map. The map itself
@@ -1085,6 +1088,22 @@ func (c *Core) Trade(pw string, form *TradeForm) (*Order, error) {
 		return nil, fmt.Errorf("unknown DEX %s", form.DEX)
 	}
 
+	// Avoid placing an order if the dexConnection is scheduled for a
+	// trade suspension.
+	//
+	// TODO: This needs further refinement, it's possible trades can be made
+	// after the suspension message is received if it starts minutes, hours or
+	// days into the future. we'll need to ensure the trades being made are
+	// handled in an epoch less than the starting epoch time for the trade
+	// suspension.
+	dc.suspensionEpochMtx.RLock()
+	scheduledSuspension := dc.suspensionEpoch != 0
+	dc.suspensionEpochMtx.RUnlock()
+	if scheduledSuspension {
+		return nil, fmt.Errorf("order placement suspended due to impending"+
+			" trade suspension for dex %s", dc.acct.url)
+	}
+
 	rate, qty := form.Rate, form.Qty
 	if form.IsLimit && rate == 0 {
 		return nil, fmt.Errorf("zero-rate order not allowed")
@@ -1918,6 +1937,21 @@ func handleMatchProofMsg(_ *Core, dc *dexConnection, msg *msgjson.Message) error
 	return ob.ValidateMatchProof(note)
 }
 
+// handleTradeSuspensionMsg is called when a trade_suspension message is received.
+func handleTradeSuspensionMsg(_ *Core, dc *dexConnection, msg *msgjson.Message) error {
+	var suspension msgjson.TradeSuspensionRequest
+	err := msg.Unmarshal(&suspension)
+	if err != nil {
+		return fmt.Errorf("trade suspenion unmarshal error: %v", err)
+	}
+
+	dc.suspensionEpochMtx.Lock()
+	dc.suspensionEpoch = suspension.Epoch
+	dc.suspensionEpochMtx.Unlock()
+
+	return nil
+}
+
 // routeHandler is a handler for a message from the DEX.
 type routeHandler func(*Core, *dexConnection, *msgjson.Message) error
 
@@ -1928,7 +1962,7 @@ var reqHandlers = map[string]routeHandler{
 	msgjson.AuditRoute:       handleAuditRoute,
 	msgjson.RedemptionRoute:  handleRedemptionRoute,
 	msgjson.RevokeMatchRoute: nil,
-	msgjson.SuspensionRoute:  nil,
+	msgjson.SuspensionRoute:  handleTradeSuspensionMsg,
 }
 
 var noteHandlers = map[string]routeHandler{

dex/msgjson/types.go

@@ -689,6 +689,12 @@ type PreimageRequest struct {
 	CommitChecksum Bytes `json:"csum"`
 }
 
+// TradeSuspensionRequest is the server-origination trade suspension payload.
+type TradeSuspensionRequest struct {
+	Epoch   uint64 `json:"epoch"`
+	Persist bool   `json:"persist"`
+}
+
 // PreimageResponse is the client-originating preimage response payload.
 type PreimageResponse struct {
 	Preimage Bytes `json:"pimg"`