examples: set socket buffers and raise tun tx_queue (#1928)

* examples: set socket buffers and raise tun tx_queue

* examples: use the default tcp max window for socket buffers

* examples: note buffers are linux only, clarify tx_queue default

* tun: default tx_queue to 5000

overlay/tun.go

@@ -43,7 +43,7 @@ type DeviceFactory func(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix,
 func NewDeviceFromConfig(c *config.C, l *slog.Logger, vpnNetworks []netip.Prefix, routines int) (Device, error) {
 	switch {
 	case c.GetBool("tun.disabled", false):
-		tun := newDisabledTun(vpnNetworks, c.GetInt("tun.tx_queue", 500), c.GetBool("stats.message_metrics", false), l)
+		tun := newDisabledTun(vpnNetworks, c.GetInt("tun.tx_queue", 5000), c.GetBool("stats.message_metrics", false), l)
 		return tun, nil
 
 	default:

overlay/tun_linux.go

@@ -221,7 +221,7 @@ func newTunGeneric(c *config.C, l *slog.Logger, fd int, vnetHdr bool, offloadFla
 		vnetHdr:                   vnetHdr,
 		offloadFlags:              offloadFlags,
 		vpnNetworks:               vpnNetworks,
-		TXQueueLen:                c.GetInt("tun.tx_queue", 500),
+		TXQueueLen:                c.GetInt("tun.tx_queue", 5000),
 		useSystemRoutes:           c.GetBool("tun.use_system_route_table", false),
 		useSystemRoutesBufferSize: c.GetInt("tun.use_system_route_table_buffer_size", 0),
 		routesFromSystem:          map[netip.Prefix]routing.Gateways{},