feat: support SO_BINDTODEVICE on Linux (#650)

Fixes #532

internal/socket/socket.go

@@ -27,24 +27,33 @@ import (
 )
 
 // Option is used for setting an option on socket.
-type Option struct {
-	SetSockOpt func(int, int) error
-	Opt        int
+type Option[T int | string] struct {
+	SetSockOpt func(int, T) error
+	Opt        T
+}
+
+func execSockOpts[T int | string](fd int, opts []Option[T]) error {
+	for _, opt := range opts {
+		if err := opt.SetSockOpt(fd, opt.Opt); err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 // TCPSocket calls the internal tcpSocket.
-func TCPSocket(proto, addr string, passive bool, sockOpts ...Option) (int, net.Addr, error) {
-	return tcpSocket(proto, addr, passive, sockOpts...)
+func TCPSocket(proto, addr string, passive bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (int, net.Addr, error) {
+	return tcpSocket(proto, addr, passive, sockOptInts, sockOptStrs)
 }
 
 // UDPSocket calls the internal udpSocket.
-func UDPSocket(proto, addr string, connect bool, sockOpts ...Option) (int, net.Addr, error) {
-	return udpSocket(proto, addr, connect, sockOpts...)
+func UDPSocket(proto, addr string, connect bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (int, net.Addr, error) {
+	return udpSocket(proto, addr, connect, sockOptInts, sockOptStrs)
 }
 
 // UnixSocket calls the internal udsSocket.
-func UnixSocket(proto, addr string, passive bool, sockOpts ...Option) (int, net.Addr, error) {
-	return udsSocket(proto, addr, passive, sockOpts...)
+func UnixSocket(proto, addr string, passive bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (int, net.Addr, error) {
+	return udsSocket(proto, addr, passive, sockOptInts, sockOptStrs)
 }
 
 // Accept accepts the next incoming socket along with setting

internal/socket/sockopts_bsd.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2024 The Gnet Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build dragonfly || freebsd || netbsd || openbsd
+// +build dragonfly freebsd netbsd openbsd
+
+package socket
+
+import errorx "github.com/panjf2000/gnet/v2/pkg/errors"
+
+// SetBindToDevice is not implemented on *BSD because there is
+// no equivalent of Linux's SO_BINDTODEVICE.
+func SetBindToDevice(_ int, _ string) error {
+	return errorx.ErrUnsupportedOp
+}

internal/socket/sockopts_darwin.go

@@ -19,6 +19,8 @@ import (
 	"os"
 
 	"golang.org/x/sys/unix"
+
+	errorx "github.com/panjf2000/gnet/v2/pkg/errors"
 )
 
 // SetKeepAlivePeriod sets whether the operating system should send
@@ -52,3 +54,9 @@ func SetKeepAlivePeriod(fd, secs int) error {
 
 	return os.NewSyscallError("setsockopt", unix.SetsockoptInt(fd, unix.IPPROTO_TCP, unix.TCP_KEEPCNT, 5))
 }
+
+// SetBindToDevice is not implemented on macOS because there is
+// no equivalent of Linux's SO_BINDTODEVICE.
+func SetBindToDevice(_ int, _ string) error {
+	return errorx.ErrUnsupportedOp
+}

internal/socket/sockopts_linux.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2024 The Gnet Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package socket
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// SetBindToDevice binds the socket to a specific network interface.
+//
+// SO_BINDTODEVICE on Linux works in both directions: only process packets
+// received from the particular interface along with sending them through
+// that interface, instead of following the default route.
+func SetBindToDevice(fd int, ifname string) error {
+	return os.NewSyscallError("setsockopt", unix.BindToDevice(fd, ifname))
+}

internal/socket/sockopts_openbsd.go

@@ -14,11 +14,11 @@
 
 package socket
 
-import "golang.org/x/sys/unix"
+import errorx "github.com/panjf2000/gnet/v2/pkg/errors"
 
 // SetKeepAlivePeriod sets whether the operating system should send
 // keep-alive messages on the connection and sets period between TCP keep-alive probes.
 func SetKeepAlivePeriod(_, _ int) error {
 	// OpenBSD has no user-settable per-socket TCP keepalive options.
-	return unix.ENOPROTOOPT
+	return errorx.ErrUnsupportedOp
 }

internal/socket/sockopts_posix.go

@@ -39,13 +39,13 @@ func SetNoDelay(fd, noDelay int) error {
 // SetRecvBuffer sets the size of the operating system's
 // receive buffer associated with the connection.
 func SetRecvBuffer(fd, size int) error {
-	return unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_RCVBUF, size)
+	return os.NewSyscallError("setsockopt", unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_RCVBUF, size))
 }
 
 // SetSendBuffer sets the size of the operating system's
 // transmit buffer associated with the connection.
 func SetSendBuffer(fd, size int) error {
-	return unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF, size)
+	return os.NewSyscallError("setsockopt", unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_SNDBUF, size))
 }
 
 // SetReuseAddr enables SO_REUSEADDR option on socket.
@@ -55,7 +55,7 @@ func SetReuseAddr(fd, reuseAddr int) error {
 
 // SetIPv6Only restricts a IPv6 socket to only process IPv6 requests or both IPv4 and IPv6 requests.
 func SetIPv6Only(fd, ipv6only int) error {
-	return unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_V6ONLY, ipv6only)
+	return os.NewSyscallError("setsockopt", unix.SetsockoptInt(fd, unix.IPPROTO_IPV6, unix.IPV6_V6ONLY, ipv6only))
 }
 
 // SetLinger sets the behavior of Close on a connection which still
@@ -79,7 +79,7 @@ func SetLinger(fd, sec int) error {
 		l.Onoff = 0
 		l.Linger = 0
 	}
-	return unix.SetsockoptLinger(fd, syscall.SOL_SOCKET, syscall.SO_LINGER, &l)
+	return os.NewSyscallError("setsockopt", unix.SetsockoptLinger(fd, syscall.SOL_SOCKET, syscall.SO_LINGER, &l))
 }
 
 // SetMulticastMembership returns with a socket option function based on the IP

internal/socket/tcp_socket.go

@@ -83,7 +83,7 @@ func determineTCPProto(proto string, addr *net.TCPAddr) (string, error) {
 
 // tcpSocket creates an endpoint for communication and returns a file descriptor that refers to that endpoint.
 // Argument `reusePort` indicates whether the SO_REUSEPORT flag will be assigned.
-func tcpSocket(proto, addr string, passive bool, sockOpts ...Option) (fd int, netAddr net.Addr, err error) {
+func tcpSocket(proto, addr string, passive bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (fd int, netAddr net.Addr, err error) {
 	var (
 		family   int
 		ipv6only bool
@@ -114,10 +114,11 @@ func tcpSocket(proto, addr string, passive bool, sockOpts ...Option) (fd int, ne
 		}
 	}
 
-	for _, sockOpt := range sockOpts {
-		if err = sockOpt.SetSockOpt(fd, sockOpt.Opt); err != nil {
-			return
-		}
+	if err = execSockOpts(fd, sockOptInts); err != nil {
+		return
+	}
+	if err = execSockOpts(fd, sockOptStrs); err != nil {
+		return
 	}
 
 	if passive {

internal/socket/udp_socket.go

@@ -81,7 +81,7 @@ func determineUDPProto(proto string, addr *net.UDPAddr) (string, error) {
 
 // udpSocket creates an endpoint for communication and returns a file descriptor that refers to that endpoint.
 // Argument `reusePort` indicates whether the SO_REUSEPORT flag will be assigned.
-func udpSocket(proto, addr string, connect bool, sockOpts ...Option) (fd int, netAddr net.Addr, err error) {
+func udpSocket(proto, addr string, connect bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (fd int, netAddr net.Addr, err error) {
 	var (
 		family   int
 		ipv6only bool
@@ -117,10 +117,11 @@ func udpSocket(proto, addr string, connect bool, sockOpts ...Option) (fd int, ne
 		return
 	}
 
-	for _, sockOpt := range sockOpts {
-		if err = sockOpt.SetSockOpt(fd, sockOpt.Opt); err != nil {
-			return
-		}
+	if err = execSockOpts(fd, sockOptInts); err != nil {
+		return
+	}
+	if err = execSockOpts(fd, sockOptStrs); err != nil {
+		return
 	}
 
 	if connect {

internal/socket/unix_socket.go

@@ -45,7 +45,7 @@ func GetUnixSockAddr(proto, addr string) (sa unix.Sockaddr, family int, unixAddr
 
 // udsSocket creates an endpoint for communication and returns a file descriptor that refers to that endpoint.
 // Argument `reusePort` indicates whether the SO_REUSEPORT flag will be assigned.
-func udsSocket(proto, addr string, passive bool, sockOpts ...Option) (fd int, netAddr net.Addr, err error) {
+func udsSocket(proto, addr string, passive bool, sockOptInts []Option[int], sockOptStrs []Option[string]) (fd int, netAddr net.Addr, err error) {
 	var (
 		family int
 		sa     unix.Sockaddr
@@ -70,10 +70,11 @@ func udsSocket(proto, addr string, passive bool, sockOpts ...Option) (fd int, ne
 		}
 	}()
 
-	for _, sockOpt := range sockOpts {
-		if err = sockOpt.SetSockOpt(fd, sockOpt.Opt); err != nil {
-			return
-		}
+	if err = execSockOpts(fd, sockOptInts); err != nil {
+		return
+	}
+	if err = execSockOpts(fd, sockOptStrs); err != nil {
+		return
 	}
 
 	if passive {

listener_unix.go

@@ -36,7 +36,8 @@ type listener struct {
 	fd               int
 	addr             net.Addr
 	address, network string
-	sockOpts         []socket.Option
+	sockOptInts      []socket.Option[int]
+	sockOptStrs      []socket.Option[string]
 	pollAttachment   *netpoll.PollAttachment // listener attachment for poller
 }
 
@@ -52,14 +53,14 @@ func (ln *listener) dup() (int, error) {
 func (ln *listener) normalize() (err error) {
 	switch ln.network {
 	case "tcp", "tcp4", "tcp6":
-		ln.fd, ln.addr, err = socket.TCPSocket(ln.network, ln.address, true, ln.sockOpts...)
+		ln.fd, ln.addr, err = socket.TCPSocket(ln.network, ln.address, true, ln.sockOptInts, ln.sockOptStrs)
 		ln.network = "tcp"
 	case "udp", "udp4", "udp6":
-		ln.fd, ln.addr, err = socket.UDPSocket(ln.network, ln.address, false, ln.sockOpts...)
+		ln.fd, ln.addr, err = socket.UDPSocket(ln.network, ln.address, false, ln.sockOptInts, ln.sockOptStrs)
 		ln.network = "udp"
 	case "unix":
 		_ = os.RemoveAll(ln.address)
-		ln.fd, ln.addr, err = socket.UnixSocket(ln.network, ln.address, true, ln.sockOpts...)
+		ln.fd, ln.addr, err = socket.UnixSocket(ln.network, ln.address, true, ln.sockOptInts, ln.sockOptStrs)
 	default:
 		err = errors.ErrUnsupportedProtocol
 	}
@@ -79,37 +80,44 @@ func (ln *listener) close() {
 }
 
 func initListener(network, addr string, options *Options) (l *listener, err error) {
-	var sockOpts []socket.Option
+	var (
+		sockOptInts []socket.Option[int]
+		sockOptStrs []socket.Option[string]
+	)
 	if options.ReusePort || strings.HasPrefix(network, "udp") {
-		sockOpt := socket.Option{SetSockOpt: socket.SetReuseport, Opt: 1}
-		sockOpts = append(sockOpts, sockOpt)
+		sockOpt := socket.Option[int]{SetSockOpt: socket.SetReuseport, Opt: 1}
+		sockOptInts = append(sockOptInts, sockOpt)
 	}
 	if options.ReuseAddr {
-		sockOpt := socket.Option{SetSockOpt: socket.SetReuseAddr, Opt: 1}
-		sockOpts = append(sockOpts, sockOpt)
+		sockOpt := socket.Option[int]{SetSockOpt: socket.SetReuseAddr, Opt: 1}
+		sockOptInts = append(sockOptInts, sockOpt)
 	}
 	if options.TCPNoDelay == TCPNoDelay && strings.HasPrefix(network, "tcp") {
-		sockOpt := socket.Option{SetSockOpt: socket.SetNoDelay, Opt: 1}
-		sockOpts = append(sockOpts, sockOpt)
+		sockOpt := socket.Option[int]{SetSockOpt: socket.SetNoDelay, Opt: 1}
+		sockOptInts = append(sockOptInts, sockOpt)
 	}
 	if options.SocketRecvBuffer > 0 {
-		sockOpt := socket.Option{SetSockOpt: socket.SetRecvBuffer, Opt: options.SocketRecvBuffer}
-		sockOpts = append(sockOpts, sockOpt)
+		sockOpt := socket.Option[int]{SetSockOpt: socket.SetRecvBuffer, Opt: options.SocketRecvBuffer}
+		sockOptInts = append(sockOptInts, sockOpt)
 	}
 	if options.SocketSendBuffer > 0 {
-		sockOpt := socket.Option{SetSockOpt: socket.SetSendBuffer, Opt: options.SocketSendBuffer}
-		sockOpts = append(sockOpts, sockOpt)
+		sockOpt := socket.Option[int]{SetSockOpt: socket.SetSendBuffer, Opt: options.SocketSendBuffer}
+		sockOptInts = append(sockOptInts, sockOpt)
 	}
 	if strings.HasPrefix(network, "udp") {
 		udpAddr, err := net.ResolveUDPAddr(network, addr)
 		if err == nil && udpAddr.IP.IsMulticast() {
 			if sockoptFn := socket.SetMulticastMembership(network, udpAddr); sockoptFn != nil {
-				sockOpt := socket.Option{SetSockOpt: sockoptFn, Opt: options.MulticastInterfaceIndex}
-				sockOpts = append(sockOpts, sockOpt)
+				sockOpt := socket.Option[int]{SetSockOpt: sockoptFn, Opt: options.MulticastInterfaceIndex}
+				sockOptInts = append(sockOptInts, sockOpt)
 			}
 		}
 	}
-	l = &listener{network: network, address: addr, sockOpts: sockOpts}
+	if options.BindToDevice != "" {
+		sockOpt := socket.Option[string]{SetSockOpt: socket.SetBindToDevice, Opt: options.BindToDevice}
+		sockOptStrs = append(sockOptStrs, sockOpt)
+	}
+	l = &listener{network: network, address: addr, sockOptInts: sockOptInts, sockOptStrs: sockOptStrs}
 	err = l.normalize()
 	return
 }

options.go

@@ -68,6 +68,12 @@ type Options struct {
 	// MulticastInterfaceIndex is the index of the interface name where the multicast UDP addresses will be bound to.
 	MulticastInterfaceIndex int
 
+	// BindToDevice is the name of the interface to which the listening socket will be bound.
+	//
+	// It is only available on Linux at the moment, an error will therefore be returned when
+	// setting this option on non-linux platforms.
+	BindToDevice string
+
 	// ============================= Options for both server-side and client-side =============================
 
 	// ReadBufferCap is the maximum number of bytes that can be read from the remote when the readable event comes.
@@ -95,7 +101,7 @@ type Options struct {
 	// Ticker indicates whether the ticker has been set up.
 	Ticker bool
 
-	// TCPKeepAlive enable the TCP keep-alive mechanism (SO_KEEPALIVE) and set its value
+	// TCPKeepAlive enables the TCP keep-alive mechanism (SO_KEEPALIVE) and set its value
 	// on TCP_KEEPIDLE, 1/5 of its value on TCP_KEEPINTVL, and 5 on TCP_KEEPCNT.
 	TCPKeepAlive time.Duration
 
@@ -270,6 +276,16 @@ func WithMulticastInterfaceIndex(idx int) Option {
 	}
 }
 
+// WithBindToDevice sets the name of the interface to which the listening socket will be bound.
+//
+// It is only available on Linux at the moment, an error will therefore be returned when
+// setting this option on non-linux platforms.
+func WithBindToDevice(iface string) Option {
+	return func(opts *Options) {
+		opts.BindToDevice = iface
+	}
+}
+
 // WithEdgeTriggeredIO enables the edge-triggered I/O for the underlying epoll/kqueue event-loop.
 func WithEdgeTriggeredIO(et bool) Option {
 	return func(opts *Options) {