Feature: support relay (proxy chains) (#539)

adapters/outboundgroup/util.go

@@ -0,0 +1,53 @@
+package outboundgroup
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	C "github.com/Dreamacro/clash/constant"
+)
+
+func addrToMetadata(rawAddress string) (addr *C.Metadata, err error) {
+	host, port, err := net.SplitHostPort(rawAddress)
+	if err != nil {
+		err = fmt.Errorf("addrToMetadata failed: %w", err)
+		return
+	}
+
+	ip := net.ParseIP(host)
+	if ip != nil {
+		if ip.To4() != nil {
+			addr = &C.Metadata{
+				AddrType: C.AtypIPv4,
+				Host:     "",
+				DstIP:    ip,
+				DstPort:  port,
+			}
+			return
+		} else {
+			addr = &C.Metadata{
+				AddrType: C.AtypIPv6,
+				Host:     "",
+				DstIP:    ip,
+				DstPort:  port,
+			}
+			return
+		}
+	} else {
+		addr = &C.Metadata{
+			AddrType: C.AtypDomainName,
+			Host:     host,
+			DstIP:    nil,
+			DstPort:  port,
+		}
+		return
+	}
+}
+
+func tcpKeepAlive(c net.Conn) {
+	if tcp, ok := c.(*net.TCPConn); ok {
+		tcp.SetKeepAlive(true)
+		tcp.SetKeepAlivePeriod(30 * time.Second)
+	}
+}