Improve: refactor ssr and fix #995 (#1189)

Co-authored-by: goomada <madao@DESKTOP-IOEBS0C.localdomain>

component/ssr/obfs/plain.go

@@ -1,25 +1,15 @@
 package obfs
 
+import "net"
+
 type plain struct{}
 
 func init() {
-	register("plain", newPlain)
+	register("plain", newPlain, 0)
 }
 
 func newPlain(b *Base) Obfs {
 	return &plain{}
 }
 
-func (p *plain) initForConn() Obfs { return &plain{} }
-
-func (p *plain) GetObfsOverhead() int {
-	return 0
-}
-
-func (p *plain) Encode(b []byte) ([]byte, error) {
-	return b, nil
-}
-
-func (p *plain) Decode(b []byte) ([]byte, bool, error) {
-	return b, false, nil
-}
+func (p *plain) StreamConn(c net.Conn) net.Conn { return c }