Routing: fix router select wrong outbound when failed to resolve domain to ip

features/routing/context.go

@@ -49,4 +49,7 @@ type Context interface {
 
 	// GetSkipDNSResolve returns a flag switch for weather skip dns resolve during route pick.
 	GetSkipDNSResolve() bool
+
+	// GetError returns errors during route pick, e.g., built-in-dns fail to resolve domain to IP
+	GetError() error
 }

features/routing/dns/context.go

@@ -1,8 +1,6 @@
 package dns
 
 import (
-	"context"
-
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
 	"github.com/xtls/xray-core/features/dns"
@@ -14,6 +12,7 @@ type ResolvableContext struct {
 	routing.Context
 	dnsClient   dns.Client
 	resolvedIPs []net.IP
+	lookupError error
 }
 
 // GetTargetIPs overrides original routing.Context's implementation.
@@ -22,6 +21,10 @@ func (ctx *ResolvableContext) GetTargetIPs() []net.IP {
 		return ctx.resolvedIPs
 	}
 
+	if ips := ctx.Context.GetTargetIPs(); len(ips) != 0 {
+		return ips
+	}
+
 	if domain := ctx.GetTargetDomain(); len(domain) != 0 {
 		ips, _, err := ctx.dnsClient.LookupIP(domain, dns.IPOption{
 			IPv4Enable: true,
@@ -32,16 +35,17 @@ func (ctx *ResolvableContext) GetTargetIPs() []net.IP {
 			ctx.resolvedIPs = ips
 			return ips
 		}
-		errors.LogInfoInner(context.Background(), err, "resolve ip for ", domain)
-	}
-
-	if ips := ctx.Context.GetTargetIPs(); len(ips) != 0 {
-		return ips
+		ctx.lookupError = errors.New("resolve ip for ", domain).Base(err)
 	}
 
 	return nil
 }
 
+// GetError override original routing.Context's implementation.
+func (ctx *ResolvableContext) GetError() error {
+	return ctx.lookupError
+}
+
 // ContextWithDNSClient creates a new routing context with domain resolving capability.
 // Resolved domain IPs can be retrieved by GetTargetIPs().
 func ContextWithDNSClient(ctx routing.Context, client dns.Client) routing.Context {

features/routing/session/context.go

@@ -152,6 +152,11 @@ func (ctx *Context) GetSkipDNSResolve() bool {
 	return ctx.Content.SkipDNSResolve
 }
 
+// GetError implements routing.Context.
+func (ctx *Context) GetError() error {
+	return nil
+}
+
 // AsRoutingContext creates a context from context.context with session info.
 func AsRoutingContext(ctx context.Context) routing.Context {
 	outbounds := session.OutboundsFromContext(ctx)