add UDPReadBufferSize option (#857)

client.go

@@ -430,6 +430,10 @@ type Client struct {
 	// at least a packet within this timeout, otherwise it switches to TCP.
 	// It defaults to 3 seconds.
 	InitialUDPReadTimeout time.Duration
+	// Size of the UDP read buffer.
+	// This can be increased to reduce packet losses.
+	// It defaults to the operating system default value.
+	UDPReadBufferSize int
 	// Size of the queue of outgoing packets.
 	// It defaults to 256.
 	WriteQueueSize int

client_udp_listener.go

@@ -2,9 +2,11 @@ package gortsplib
 
 import (
 	"crypto/rand"
+	"fmt"
 	"math/big"
 	"net"
 	"sync/atomic"
+	"syscall"
 	"time"
 
 	"github.com/bluenviron/gortsplib/v4/pkg/multicast"
@@ -25,7 +27,43 @@ func randInRange(maxVal int) (int, error) {
 
 type packetConn interface {
 	net.PacketConn
-	SetReadBuffer(int) error
+	SyscallConn() (syscall.RawConn, error)
+}
+
+func setAndVerifyReadBufferSize(pc packetConn, v int) error {
+	rawConn, err := pc.SyscallConn()
+	if err != nil {
+		panic(err)
+	}
+
+	var err2 error
+
+	err = rawConn.Control(func(fd uintptr) {
+		err2 = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUF, v)
+		if err2 != nil {
+			return
+		}
+
+		var v2 int
+		v2, err2 = syscall.GetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUF)
+		if err2 != nil {
+			return
+		}
+
+		if v2 != (v * 2) {
+			err2 = fmt.Errorf("unable to set read buffer size to %v - check that net.core.rmem_max is greater than %v", v, v)
+			return
+		}
+	})
+	if err != nil {
+		return err
+	}
+
+	if err2 != nil {
+		return err2
+	}
+
+	return nil
 }
 
 type clientUDPListener struct {
@@ -61,10 +99,12 @@ func (u *clientUDPListener) initialize() error {
 		u.pc = tmp.(*net.UDPConn)
 	}
 
-	err := u.pc.SetReadBuffer(udpKernelReadBufferSize)
+	if u.c.UDPReadBufferSize != 0 {
-	if err != nil {
+		err := setAndVerifyReadBufferSize(u.pc, u.c.UDPReadBufferSize)
-		u.pc.Close()
+		if err != nil {
-		return err
+			u.pc.Close()
+			return err
+		}
 	}
 
 	u.lastPacketTime = int64Ptr(0)

constants.go

@@ -1,9 +1,6 @@
 package gortsplib
 
 const (
-	// same size as GStreamer's rtspsrc
-	udpKernelReadBufferSize = 0x80000
-
 	// 1500 (UDP MTU) - 20 (IP header) - 8 (UDP header)
 	udpMaxPayloadSize = 1472
 

pkg/multicast/multi_conn.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"syscall"
 	"time"
 
 	"golang.org/x/net/ipv4"
@@ -133,6 +134,11 @@ func (c *multiConn) SetReadBuffer(bytes int) error {
 	return c.readConn.SetReadBuffer(bytes)
 }
 
+// SyscallConn implements Conn.
+func (c *multiConn) SyscallConn() (syscall.RawConn, error) {
+	return c.readConn.SyscallConn()
+}
+
 // LocalAddr implements Conn.
 func (c *multiConn) LocalAddr() net.Addr {
 	return c.readConn.LocalAddr()

pkg/multicast/multi_conn_lin.go

@@ -187,6 +187,11 @@ func (c *multiConn) SetReadBuffer(bytes int) error {
 	return syscall.SetsockoptInt(int(c.readFile.Fd()), syscall.SOL_SOCKET, syscall.SO_RCVBUF, bytes)
 }
 
+// SyscallConn implements Conn.
+func (c *multiConn) SyscallConn() (syscall.RawConn, error) {
+	return &rawConn{fd: c.readFile.Fd()}, nil
+}
+
 // LocalAddr implements Conn.
 func (c *multiConn) LocalAddr() net.Addr {
 	return c.readConn.LocalAddr()

pkg/multicast/multicast.go

@@ -4,12 +4,14 @@ package multicast
 import (
 	"fmt"
 	"net"
+	"syscall"
 )
 
 // Conn is a Multicast connection.
 type Conn interface {
 	net.PacketConn
 	SetReadBuffer(int) error
+	SyscallConn() (syscall.RawConn, error)
 }
 
 // InterfaceForSource returns a multicast-capable interface that can communicate with given IP.

pkg/multicast/single_conn.go

@@ -5,6 +5,7 @@ package multicast
 import (
 	"net"
 	"strconv"
+	"syscall"
 	"time"
 
 	"golang.org/x/net/ipv4"
@@ -77,6 +78,11 @@ func (c *singleConn) SetReadBuffer(bytes int) error {
 	return c.conn.SetReadBuffer(bytes)
 }
 
+// SyscallConn implements Conn.
+func (c *singleConn) SyscallConn() (syscall.RawConn, error) {
+	return c.conn.SyscallConn()
+}
+
 // LocalAddr implements Conn.
 func (c *singleConn) LocalAddr() net.Addr {
 	return c.conn.LocalAddr()

pkg/multicast/single_conn_lin.go

@@ -41,6 +41,26 @@ func setIPMreqInterface(mreq *syscall.IPMreq, ifi *net.Interface) error {
 	return fmt.Errorf("no such interface")
 }
 
+type rawConn struct {
+	fd uintptr
+}
+
+// Control implements syscall.RawConn.
+func (c *rawConn) Control(f func(fd uintptr)) error {
+	f(c.fd)
+	return nil
+}
+
+// Read implements syscall.RawConn.
+func (*rawConn) Read(_ func(fd uintptr) (done bool)) error {
+	panic("unimplemented")
+}
+
+// Write implements syscall.RawConn.
+func (*rawConn) Write(_ func(fd uintptr) (done bool)) error {
+	panic("unimplemented")
+}
+
 // singleConn is a multicast connection
 // that works on a single interface.
 type singleConn struct {
@@ -141,6 +161,11 @@ func (c *singleConn) SetReadBuffer(bytes int) error {
 	return syscall.SetsockoptInt(int(c.file.Fd()), syscall.SOL_SOCKET, syscall.SO_RCVBUF, bytes)
 }
 
+// SyscallConn implements Conn.
+func (c *singleConn) SyscallConn() (syscall.RawConn, error) {
+	return &rawConn{fd: c.file.Fd()}, nil
+}
+
 // LocalAddr implements Conn.
 func (c *singleConn) LocalAddr() net.Addr {
 	return c.conn.LocalAddr()

server.go

@@ -85,6 +85,10 @@ type Server struct {
 	WriteTimeout time.Duration
 	// a TLS configuration to accept TLS (RTSPS) connections.
 	TLSConfig *tls.Config
+	// Size of the UDP read buffer.
+	// This can be increased to reduce packet losses.
+	// It defaults to the operating system default value.
+	UDPReadBufferSize int
 	// Size of the queue of outgoing packets.
 	// It defaults to 256.
 	WriteQueueSize int
@@ -225,6 +229,7 @@ func (s *Server) Start() error {
 		}
 
 		s.udpRTPListener = &serverUDPListener{
+			readBufferSize:  s.UDPReadBufferSize,
 			listenPacket:    s.ListenPacket,
 			writeTimeout:    s.WriteTimeout,
 			multicastEnable: false,
@@ -236,6 +241,7 @@ func (s *Server) Start() error {
 		}
 
 		s.udpRTCPListener = &serverUDPListener{
+			readBufferSize:  s.UDPReadBufferSize,
 			listenPacket:    s.ListenPacket,
 			writeTimeout:    s.WriteTimeout,
 			multicastEnable: false,

server_multicast_writer.go

@@ -23,6 +23,7 @@ func (h *serverMulticastWriter) initialize() error {
 	}
 
 	rtpl, rtcpl, err := createUDPListenerMulticastPair(
+		h.s.UDPReadBufferSize,
 		h.s.ListenPacket,
 		h.s.WriteTimeout,
 		h.s.MulticastRTPPort,

server_udp_listener.go

@@ -26,6 +26,7 @@ func (p *clientAddr) fill(ip net.IP, port int) {
 }
 
 func createUDPListenerMulticastPair(
+	readBufferSize int,
 	listenPacket func(network, address string) (net.PacketConn, error),
 	writeTimeout time.Duration,
 	multicastRTPPort int,
@@ -33,6 +34,7 @@ func createUDPListenerMulticastPair(
 	ip net.IP,
 ) (*serverUDPListener, *serverUDPListener, error) {
 	rtpl := &serverUDPListener{
+		readBufferSize:  readBufferSize,
 		listenPacket:    listenPacket,
 		writeTimeout:    writeTimeout,
 		multicastEnable: true,
@@ -44,6 +46,7 @@ func createUDPListenerMulticastPair(
 	}
 
 	rtcpl := &serverUDPListener{
+		readBufferSize:  readBufferSize,
 		listenPacket:    listenPacket,
 		writeTimeout:    writeTimeout,
 		multicastEnable: true,
@@ -59,6 +62,7 @@ func createUDPListenerMulticastPair(
 }
 
 type serverUDPListener struct {
+	readBufferSize  int
 	listenPacket    func(network, address string) (net.PacketConn, error)
 	writeTimeout    time.Duration
 	multicastEnable bool
@@ -94,10 +98,12 @@ func (u *serverUDPListener) initialize() error {
 		u.listenIP = tmp.LocalAddr().(*net.UDPAddr).IP
 	}
 
-	err := u.pc.SetReadBuffer(udpKernelReadBufferSize)
+	if u.readBufferSize != 0 {
-	if err != nil {
+		err := setAndVerifyReadBufferSize(u.pc, u.readBufferSize)
-		u.pc.Close()
+		if err != nil {
-		return err
+			u.pc.Close()
+			return err
+		}
 	}
 
 	u.clients = make(map[clientAddr]readFunc)