handleInterfaceError handles interface lookup errors on mobile platforms.

Author: DrewCyber

src/core/link_tcp.go

@@ -69,14 +69,14 @@ func (l *linkTCP) dialerFor(dst *net.TCPAddr, sintf string) (*net.Dialer, error)
 		dialer.Control = l.getControl(sintf)
 		ief, err := net.InterfaceByName(sintf)
 		if err != nil {
-			return nil, fmt.Errorf("interface %q not found", sintf)
+			return l.handleInterfaceError(err, sintf, dst, dialer)
 		}
 		if ief.Flags&net.FlagUp == 0 {
 			return nil, fmt.Errorf("interface %q is not up", sintf)
 		}
 		addrs, err := ief.Addrs()
 		if err != nil {
-			return nil, fmt.Errorf("interface %q addresses not available: %w", sintf, err)
+			return l.handleInterfaceError(err, sintf, dst, dialer)
 		}
 		for addrindex, addr := range addrs {
 			src, _, err := net.ParseCIDR(addr.String())
@@ -104,6 +104,10 @@ func (l *linkTCP) dialerFor(dst *net.TCPAddr, sintf string) (*net.Dialer, error)
 			}
 		}
 		if dialer.LocalAddr == nil {
+			// Mobile platform workaround: proceed without source binding if link-local
+			if dst.IP.IsLinkLocalUnicast() && dst.Zone != "" {
+				return dialer, nil
+			}
 			return nil, fmt.Errorf("no suitable source address found on interface %q", sintf)
 		}
 	}

src/core/link_tcp_default.go

@@ -0,0 +1,15 @@
+//go:build !android && !ios
+
+package core
+
+import (
+	"fmt"
+	"net"
+)
+
+// handleInterfaceError handles interface lookup errors on desktop platforms.
+// On desktop systems, InterfaceByName failure is a genuine error that should
+// be reported, as these platforms don't have the same restrictions as mobile.
+func (l *linkTCP) handleInterfaceError(err error, sintf string, dst *net.TCPAddr, dialer *net.Dialer) (*net.Dialer, error) {
+	return nil, fmt.Errorf("interface %q not found: %w", sintf, err)
+}

src/core/link_tcp_mobile.go

@@ -0,0 +1,22 @@
+//go:build android || ios
+
+package core
+
+import (
+	"fmt"
+	"net"
+)
+
+// handleInterfaceError handles interface lookup errors on mobile platforms.
+// On Android/iOS, InterfaceByName may fail due to permission restrictions
+// (SELinux on Android), but for link-local addresses with zone identifiers,
+// the zone is sufficient for routing and we can proceed without source binding.
+func (l *linkTCP) handleInterfaceError(err error, sintf string, dst *net.TCPAddr, dialer *net.Dialer) (*net.Dialer, error) {
+	// For link-local addresses with zone set, we can proceed without binding
+	// The zone identifier tells the kernel which interface to use
+	if dst.IP.IsLinkLocalUnicast() && dst.Zone != "" {
+		return dialer, nil
+	}
+	// For other cases, return the original error
+	return nil, fmt.Errorf("interface %q not found: %w", sintf, err)
+}