From 144f66574706c9e251c964b694e80406206cb10b Mon Sep 17 00:00:00 2001
From: Mikhail Osipov <mike.osipov@gmail.com>
Date: Mon, 6 Jul 2020 00:53:18 +0300
Subject: single socket option

---
 USAGE                       |  8 ++++++--
 pkg/server/socket/socket.go |  4 ++++
 pkg/server/socket/tun.go    |  2 ++
 pkg/server/tunnel.go        | 29 +++++++++++++++++++----------
 4 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/USAGE b/USAGE
index bd9a8a4..889c477 100644
--- a/USAGE
+++ b/USAGE
@@ -1,4 +1,8 @@
-1. Transparent proxy using redirect
+# Simple tcp tunnel
+
+tunnel add srcport,listen [dsthost:]dstport
+
+# Transparent proxy using redirect
 
 iptables -t nat -A OUTPUT -p tcp -d 198.145.29.83 -j REDIRECT --to-port 4000
 
@@ -10,6 +14,6 @@ BUGS:
 	Direct connection also possible. In this case original.addr will be equal to listen address.
 	This happens when ipv4 is used.
 
-2. Transparent proxy using tproxy
+# Transparent proxy using tproxy
 
 - todo
diff --git a/pkg/server/socket/socket.go b/pkg/server/socket/socket.go
index b419468..62ce5cf 100644
--- a/pkg/server/socket/socket.go
+++ b/pkg/server/socket/socket.go
@@ -25,6 +25,10 @@ type S interface {
 	Close()
 }
 
+type Single interface {
+	Single()
+}
+
 type conn struct {
 	net.Conn
 
diff --git a/pkg/server/socket/tun.go b/pkg/server/socket/tun.go
index 7336c04..d48c30c 100644
--- a/pkg/server/socket/tun.go
+++ b/pkg/server/socket/tun.go
@@ -43,6 +43,8 @@ func (s *tunSocket) String() string {
 	return fmt.Sprintf("tun/%s", s.name)
 }
 
+func (s *tunSocket) Single() {}
+
 func (s *tunSocket) Open(env.Env) (Conn, error) {
 	fd, err := unix.Open("/dev/net/tun", unix.O_RDWR, 0)
 	if err != nil {
diff --git a/pkg/server/tunnel.go b/pkg/server/tunnel.go
index ccd501e..afd35d8 100644
--- a/pkg/server/tunnel.go
+++ b/pkg/server/tunnel.go
@@ -373,6 +373,10 @@ func newTunnel(limit int, args []string, env env.Env) (*tunnel, error) {
 		return nil, err
 	}
 
+	if _, ok := in.(socket.Single); ok {
+		limit = 1
+	}
+
 	if out, err = socket.New(args[n]); err != nil {
 		in.Close()
 		return nil, err
@@ -406,12 +410,16 @@ func isOkTunnelName(s string) bool {
 }
 
 func tunnelAdd(r *request) {
+	limit := maxQueueLimit
+
 	args := r.args
 	name := ""
-	limit := 1
 
 	for len(args) > 1 {
-		if args[0] == "name" {
+		noarg := false
+
+		switch args[0] {
+		case "name":
 			name = args[1]
 			if !isOkTunnelName(name) {
 				r.Fatal("bad name")
@@ -422,25 +430,26 @@ func tunnelAdd(r *request) {
 			}
 
 			args = args[2:]
-			continue
-		}
 
-		if args[0] == "limit" {
+		case "limit":
 			if n, _ := strconv.Atoi(args[1]); n > 0 && n < maxQueueLimit {
 				limit = n
 			} else {
 				r.Fatal("bad limit")
 			}
 			args = args[2:]
-		}
 
-		if args[0] == "unlim" {
-			limit = maxQueueLimit
+		case "single":
+			limit = 1
 			args = args[1:]
-			continue
+
+		default:
+			noarg = true
 		}
 
-		break
+		if noarg {
+			break
+		}
 	}
 
 	if len(args) < 2 {
-- 
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