move SNI to separate package for both client and server

rvpn/server/listener_generic.go

@@ -18,6 +18,7 @@ import (
 	"github.com/gorilla/websocket"
 
 	"git.daplie.com/Daplie/go-rvpn-server/rvpn/packer"
+	"git.daplie.com/Daplie/go-rvpn-server/rvpn/sni"
 )
 
 type contextKey string
@@ -160,7 +161,7 @@ func handleConnection(ctx context.Context, wConn *WedgeConn) {
 		wssHostName := ctx.Value(ctxWssHostName).(string)
 		adminHostName := ctx.Value(ctxAdminHostName).(string)
 
-		sniHostName, err := getHello(peek)
+		sniHostName, err := sni.GetHostname(peek)
 		if err != nil {
 			loginfo.Println(err)
 			return

rvpn/sni/tls_get_hostname.go

@@ -1,10 +1,11 @@
-package server
+package sni
 
 import (
 	"errors"
 )
 
-func getHello(b []byte) (string, error) {
+// GetHostname uses SNI to determine the intended target of a new TLS connection.
+func GetHostname(b []byte) (string, error) {
 	rest := b[5:]
 	current := 0
 	handshakeType := rest[0]