From 31c23056544b2575e93b27e56e01748f426c2025 Mon Sep 17 00:00:00 2001
From: fsiegmund <siegmund@slb.com>
Date: Fri, 17 Jun 2022 14:26:23 +0100
Subject: [PATCH] UDP buffer size override with CHISEL_UDP_MAX_SIZE environment
 variable

---
 share/tunnel/tunnel_in_proxy_udp.go | 6 ++++--
 share/tunnel/tunnel_out_ssh_udp.go  | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/share/tunnel/tunnel_in_proxy_udp.go b/share/tunnel/tunnel_in_proxy_udp.go
index 35811c50..3f3fa8be 100644
--- a/share/tunnel/tunnel_in_proxy_udp.go
+++ b/share/tunnel/tunnel_in_proxy_udp.go
@@ -45,7 +45,9 @@ func listenUDP(l *cio.Logger, sshTun sshTunnel, remote *settings.Remote) (*udpLi
 		sshTun:  sshTun,
 		remote:  remote,
 		inbound: conn,
+		maxMTU:  settings.EnvInt("UDP_MAX_SIZE", 9012),
 	}
+	u.Debugf("UDP max size: %d bytes", u.maxMTU)
 	return u, nil
 }
 
@@ -57,6 +59,7 @@ type udpListener struct {
 	outboundMut sync.Mutex
 	outbound    *udpChannel
 	sent, recv  int64
+	maxMTU      int
 }
 
 func (u *udpListener) run(ctx context.Context) error {
@@ -80,8 +83,7 @@ func (u *udpListener) run(ctx context.Context) error {
 }
 
 func (u *udpListener) runInbound(ctx context.Context) error {
-	const maxMTU = 9012
-	buff := make([]byte, maxMTU)
+	buff := make([]byte, u.maxMTU)
 	for !isDone(ctx) {
 		//read from inbound udp
 		u.inbound.SetReadDeadline(time.Now().Add(time.Second))
diff --git a/share/tunnel/tunnel_out_ssh_udp.go b/share/tunnel/tunnel_out_ssh_udp.go
index 20a10a63..d3c4c62f 100644
--- a/share/tunnel/tunnel_out_ssh_udp.go
+++ b/share/tunnel/tunnel_out_ssh_udp.go
@@ -27,7 +27,9 @@ func (t *Tunnel) handleUDP(l *cio.Logger, rwc io.ReadWriteCloser, hostPort strin
 			c: rwc,
 		},
 		udpConns: conns,
+		maxMTU:   settings.EnvInt("UDP_MAX_SIZE", 9012),
 	}
+	h.Debugf("UDP max size: %d bytes", h.maxMTU)
 	for {
 		p := udpPacket{}
 		if err := h.handleWrite(&p); err != nil {
@@ -41,6 +43,7 @@ type udpHandler struct {
 	hostPort string
 	*udpChannel
 	*udpConns
+	maxMTU int
 }
 
 func (h *udpHandler) handleWrite(p *udpPacket) error {
@@ -77,8 +80,7 @@ func (h *udpHandler) handleWrite(p *udpPacket) error {
 func (h *udpHandler) handleRead(p *udpPacket, conn *udpConn) {
 	//ensure connection is cleaned up
 	defer h.udpConns.remove(conn.id)
-	const maxMTU = 9012
-	buff := make([]byte, maxMTU)
+	buff := make([]byte, h.maxMTU)
 	for {
 		//response must arrive within 15 seconds
 		deadline := settings.EnvDuration("UDP_DEADLINE", 15*time.Second)