feat: Waku v2 bridge

Issue #12610

vendor/github.com/pion/transport/vnet/.gitignore

@@ -0,0 +1 @@
+*.sw[poe]

vendor/github.com/pion/transport/vnet/README.md

@@ -0,0 +1,239 @@
+# vnet
+A virtual network layer for pion.
+
+## Overview
+
+### Goals
+* To make NAT traversal tests easy.
+* To emulate packet impairment at application level for testing.
+* To monitor packets at specified arbitrary interfaces.
+
+### Features
+* Configurable virtual LAN and WAN
+* Virtually hosted ICE servers
+
+### Virtual network components
+
+#### Top View
+```
+                           ......................................
+                           :         Virtual Network (vnet)     :
+                           :                                    :
+   +-------+ *         1 +----+         +--------+              :
+   | :App  |------------>|:Net|--o<-----|:Router |              :
+   +-------+             +----+         |        |              :
+   +-----------+ *     1 +----+         |        |              :
+   |:STUNServer|-------->|:Net|--o<-----|        |              :
+   +-----------+         +----+         |        |              :
+   +-----------+ *     1 +----+         |        |              :
+   |:TURNServer|-------->|:Net|--o<-----|        |              :
+   +-----------+         +----+ [1]     |        |              :
+                           :          1 |        | 1  <<has>>   :
+                           :      +---<>|        |<>----+ [2]   :
+                           :      |     +--------+      |       :
+                         To form  |      *|             v 0..1  :
+                   a subnet tree  |       o [3]      +-----+    :
+                           :      |       ^          |:NAT |    :
+                           :      |       |          +-----+    :
+                           :      +-------+                     :
+                           ......................................
+    Note:
+        o: NIC (Netork Interface Controller)
+      [1]: Net implments NIC interface.
+      [2]: Root router has no NAT. All child routers have a NAT always.
+      [3]: Router implements NIC interface for accesses from the
+           parent router.
+```
+
+#### Net
+Net provides 3 interfaces:
+* Configuration API (direct)
+* Network API via Net (equivalent to net.Xxx())
+* Router access via NIC interface
+```
+                   (Pion module/app, ICE servers, etc.)
+                             +-----------+
+                             |   :App    |
+                             +-----------+
+                                 * | 
+                                   | <<uses>>
+                                 1 v
+   +---------+ 1           * +-----------+ 1    * +-----------+ 1    * +------+
+ ..| :Router |----+------>o--|   :Net    |<>------|:Interface |<>------|:Addr |
+   +---------+    |      NIC +-----------+        +-----------+        +------+
+                  | <<interface>>               (vnet.Interface)      (net.Addr)
+                  |
+                  |        * +-----------+ 1    * +-----------+ 1    * +------+
+                  +------>o--|  :Router  |<>------|:Interface |<>------|:Addr |
+                         NIC +-----------+        +-----------+        +------+
+                    <<interface>>               (vnet.Interface)      (net.Addr)
+```
+
+> The instance of `Net` will be the one passed around the project.
+> Net class has public methods for configuration and for application use.
+
+
+## Implementation
+
+### Design Policy
+* Each pion package should have config object which has `Net` (of type vnet.Net) property. (just like how
+        we distribute `LoggerFactory` throughout the pion project.
+* DNS => a simple dictionary (global)?
+* Each Net has routing capability (a goroutine)
+* Use interface provided net package as much as possible
+* Routers are connected in a tree structure (no loop is allowed)
+   - To simplify routing
+   - Easy to control / monitor (stats, etc)
+* Root router has no NAT (== Internet / WAN)
+* Non-root router has a NAT always
+* When a Net is instantiated, it will automatically add `lo0` and `eth0` interface, and `lo0` will
+have one IP address, 127.0.0.1. (this is not used in pion/ice, however)
+* When a Net is added to a router, the router automatically assign an IP address for `eth0`
+interface.
+   - For simplicity
+* User data won't fragment, but optionally drop chunk larger than MTU
+* IPv6 is not supported
+
+### Basic steps for setting up virtual network
+1. Create a root router (WAN)
+1. Create child routers and add to its parent (forms a tree, don't create a loop!)
+1. Add instances of Net to each routers
+1. Call Stop(), or Stop(), on the top router, which propages all other routers
+
+#### Example: WAN with one endpoint (vnet)
+```go
+import (
+	"net"
+
+	"github.com/pion/transport/vnet"
+	"github.com/pion/logging"
+)
+
+// Create WAN (a root router).
+wan, err := vnet.NewRouter(&RouterConfig{
+    CIDR:          "0.0.0.0/0",
+    LoggerFactory: logging.NewDefaultLoggerFactory(),
+})
+
+// Create a network.
+// You can specify a static IP for the instance of Net to use. If not specified,
+// router will assign an IP address that is contained in the router's CIDR.
+nw := vnet.NewNet(&vnet.NetConfig{
+    StaticIP: "27.1.2.3",
+})
+
+// Add the network to the router.
+// The router will assign an IP address to `nw`.
+if err = wan.AddNet(nw); err != nil {
+    // handle error
+}
+
+// Start router.
+// This will start internal goroutine to route packets.
+// If you set child routers (using AddRouter), the call on the root router
+// will start the rest of routers for you.
+if err = wan.Start(); err != nil {
+    // handle error
+}
+
+//
+// Your application runs here using `nw`.
+//
+
+// Stop the router.
+// This will stop all internal goroutines in the router tree.
+// (No need to call Stop() on child routers)
+if err = wan.Stop(); err != nil {
+    // handle error
+}
+```
+
+#### Example of how to pass around the instance of vnet.Net
+The instance of vnet.Net wraps a subset of net package to enable operations
+on the virtual network. Your project must be able to pass the instance to
+all your routines that do network operation with net package. A typical way
+is to use a config param to create your instances with the virtual network
+instance (`nw` in the above example) like this:
+
+```go
+type AgentConfig struct {
+    :
+    Net:  *vnet.Net,
+}
+
+type Agent struct {
+     :
+    net:  *vnet.Net,
+}
+
+func NetAgent(config *AgentConfig) *Agent {
+    if config.Net == nil {
+        config.Net = vnet.NewNet(nil) // defaults to native operation
+    }
+    
+    return &Agent {
+         :
+        net: config.Net,
+    }
+}
+```
+
+```go
+// a.net is the instance of vnet.Net class
+func (a *Agent) listenUDP(...) error {
+    conn, err := a.net.ListenPacket(udpString, ...)
+    if err != nil {
+        return nil, err
+    }
+      :
+}
+```
+
+
+### Compatibility and Support Status
+
+|`net`<br>(built-in)|`vnet`|Note|
+|---|---|---|
+|net.Interfaces()|a.net.Interfaces()||
+|net.InterfaceByName()|a.net.InterfaceByName()||
+|net.ResolveUDPAddr()|a.net.ResolveUDPAddr()||
+|net.ListenPacket()|a.net.ListenPacket()||
+|net.ListenUDP()|a.net.ListenUDP()|(ListenPacket() is recommended)|
+|net.Listen()|a.net.Listen()|(TODO)|
+|net.ListenTCP()|(not supported)|(Listen() would be recommended)|
+|net.Dial()|a.net.Dial()||
+|net.DialUDP()|a.net.DialUDP()||
+|net.DialTCP()|(not supported)||
+|net.Interface|vnet.Interface||
+|net.PacketConn|(use it as-is)||
+|net.UDPConn|vnet.UDPConn|Use vnet.UDPPacketConn in your code|
+|net.TCPConn|vnet.TCPConn|(TODO)|Use net.Conn in your code|
+|net.Dialer|vnet.Dialer|Use a.net.CreateDialer() to create it.<br>The use of vnet.Dialer is currently experimental.|
+
+> `a.net` is an instance of Net class, and types are defined under the package name `vnet`
+
+> Most of other `interface` types in net package can be used as is.
+
+> Please post a github issue when other types/methods need to be added to vnet/vnet.Net.
+
+## TODO / Next Step
+* Implement TCP (TCPConn, Listen)
+* Support of IPv6
+* Write a bunch of examples for building virtual networks.
+* Add network impairment features (on Router)
+  - Introduce lantecy / jitter
+  - Packet filtering handler (allow selectively drop packets, etc.)
+* Add statistics data retrieval
+  - Total number of packets forward by each router
+  - Total number of packet loss
+  - Total number of connection failure (TCP)
+
+## References
+* [Comparing Simulated Packet Loss and RealWorld Network Congestion](https://www.riverbed.com/document/fpo/WhitePaper-Riverbed-SimulatedPacketLoss.pdf)
+
+### Code experiments
+* [CIDR and IPMask](https://play.golang.org/p/B7OBhkZqjmj)
+* [Test with net.IP](https://play.golang.org/p/AgXd23wKY4W)
+* [ListenPacket](https://play.golang.org/p/d4vasbnRimQ)
+* [isDottedIP()](https://play.golang.org/p/t4aZ47TgJfO)
+* [SplitHostPort](https://play.golang.org/p/JtvurlcMbhn)

vendor/github.com/pion/transport/vnet/chunk.go

@@ -0,0 +1,283 @@
+package vnet
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+type tcpFlag uint8
+
+const (
+	tcpFIN tcpFlag = 0x01
+	tcpSYN tcpFlag = 0x02
+	tcpRST tcpFlag = 0x04
+	tcpPSH tcpFlag = 0x08
+	tcpACK tcpFlag = 0x10
+)
+
+func (f tcpFlag) String() string {
+	var sa []string
+	if f&tcpFIN != 0 {
+		sa = append(sa, "FIN")
+	}
+	if f&tcpSYN != 0 {
+		sa = append(sa, "SYN")
+	}
+	if f&tcpRST != 0 {
+		sa = append(sa, "RST")
+	}
+	if f&tcpPSH != 0 {
+		sa = append(sa, "PSH")
+	}
+	if f&tcpACK != 0 {
+		sa = append(sa, "ACK")
+	}
+
+	return strings.Join(sa, "-")
+}
+
+// Generate a base36-encoded unique tag
+// See: https://play.golang.org/p/0ZaAID1q-HN
+var assignChunkTag = func() func() string { //nolint:gochecknoglobals
+	var tagCtr uint64
+
+	return func() string {
+		n := atomic.AddUint64(&tagCtr, 1)
+		return strconv.FormatUint(n, 36)
+	}
+}()
+
+// Chunk represents a packet passed around in the vnet
+type Chunk interface {
+	setTimestamp() time.Time                 // used by router
+	getTimestamp() time.Time                 // used by router
+	getSourceIP() net.IP                     // used by router
+	getDestinationIP() net.IP                // used by router
+	setSourceAddr(address string) error      // used by nat
+	setDestinationAddr(address string) error // used by nat
+
+	SourceAddr() net.Addr
+	DestinationAddr() net.Addr
+	UserData() []byte
+	Tag() string
+	Clone() Chunk
+	Network() string // returns "udp" or "tcp"
+	String() string
+}
+
+type chunkIP struct {
+	timestamp     time.Time
+	sourceIP      net.IP
+	destinationIP net.IP
+	tag           string
+}
+
+func (c *chunkIP) setTimestamp() time.Time {
+	c.timestamp = time.Now()
+	return c.timestamp
+}
+
+func (c *chunkIP) getTimestamp() time.Time {
+	return c.timestamp
+}
+
+func (c *chunkIP) getDestinationIP() net.IP {
+	return c.destinationIP
+}
+
+func (c *chunkIP) getSourceIP() net.IP {
+	return c.sourceIP
+}
+
+func (c *chunkIP) Tag() string {
+	return c.tag
+}
+
+type chunkUDP struct {
+	chunkIP
+	sourcePort      int
+	destinationPort int
+	userData        []byte
+}
+
+func newChunkUDP(srcAddr, dstAddr *net.UDPAddr) *chunkUDP {
+	return &chunkUDP{
+		chunkIP: chunkIP{
+			sourceIP:      srcAddr.IP,
+			destinationIP: dstAddr.IP,
+			tag:           assignChunkTag(),
+		},
+		sourcePort:      srcAddr.Port,
+		destinationPort: dstAddr.Port,
+	}
+}
+
+func (c *chunkUDP) SourceAddr() net.Addr {
+	return &net.UDPAddr{
+		IP:   c.sourceIP,
+		Port: c.sourcePort,
+	}
+}
+
+func (c *chunkUDP) DestinationAddr() net.Addr {
+	return &net.UDPAddr{
+		IP:   c.destinationIP,
+		Port: c.destinationPort,
+	}
+}
+
+func (c *chunkUDP) UserData() []byte {
+	return c.userData
+}
+
+func (c *chunkUDP) Clone() Chunk {
+	var userData []byte
+	if c.userData != nil {
+		userData = make([]byte, len(c.userData))
+		copy(userData, c.userData)
+	}
+
+	return &chunkUDP{
+		chunkIP: chunkIP{
+			timestamp:     c.timestamp,
+			sourceIP:      c.sourceIP,
+			destinationIP: c.destinationIP,
+			tag:           c.tag,
+		},
+		sourcePort:      c.sourcePort,
+		destinationPort: c.destinationPort,
+		userData:        userData,
+	}
+}
+
+func (c *chunkUDP) Network() string {
+	return udpString
+}
+
+func (c *chunkUDP) String() string {
+	src := c.SourceAddr()
+	dst := c.DestinationAddr()
+	return fmt.Sprintf("%s chunk %s %s => %s",
+		src.Network(),
+		c.tag,
+		src.String(),
+		dst.String(),
+	)
+}
+
+func (c *chunkUDP) setSourceAddr(address string) error {
+	addr, err := net.ResolveUDPAddr(udpString, address)
+	if err != nil {
+		return err
+	}
+	c.sourceIP = addr.IP
+	c.sourcePort = addr.Port
+	return nil
+}
+
+func (c *chunkUDP) setDestinationAddr(address string) error {
+	addr, err := net.ResolveUDPAddr(udpString, address)
+	if err != nil {
+		return err
+	}
+	c.destinationIP = addr.IP
+	c.destinationPort = addr.Port
+	return nil
+}
+
+type chunkTCP struct {
+	chunkIP
+	sourcePort      int
+	destinationPort int
+	flags           tcpFlag // control bits
+	userData        []byte  // only with PSH flag
+	// seq             uint32  // always starts with 0
+	// ack             uint32  // always starts with 0
+}
+
+func newChunkTCP(srcAddr, dstAddr *net.TCPAddr, flags tcpFlag) *chunkTCP {
+	return &chunkTCP{
+		chunkIP: chunkIP{
+			sourceIP:      srcAddr.IP,
+			destinationIP: dstAddr.IP,
+			tag:           assignChunkTag(),
+		},
+		sourcePort:      srcAddr.Port,
+		destinationPort: dstAddr.Port,
+		flags:           flags,
+	}
+}
+
+func (c *chunkTCP) SourceAddr() net.Addr {
+	return &net.TCPAddr{
+		IP:   c.sourceIP,
+		Port: c.sourcePort,
+	}
+}
+
+func (c *chunkTCP) DestinationAddr() net.Addr {
+	return &net.TCPAddr{
+		IP:   c.destinationIP,
+		Port: c.destinationPort,
+	}
+}
+
+func (c *chunkTCP) UserData() []byte {
+	return c.userData
+}
+
+func (c *chunkTCP) Clone() Chunk {
+	userData := make([]byte, len(c.userData))
+	copy(userData, c.userData)
+
+	return &chunkTCP{
+		chunkIP: chunkIP{
+			timestamp:     c.timestamp,
+			sourceIP:      c.sourceIP,
+			destinationIP: c.destinationIP,
+		},
+		sourcePort:      c.sourcePort,
+		destinationPort: c.destinationPort,
+		userData:        userData,
+	}
+}
+
+func (c *chunkTCP) Network() string {
+	return "tcp"
+}
+
+func (c *chunkTCP) String() string {
+	src := c.SourceAddr()
+	dst := c.DestinationAddr()
+	return fmt.Sprintf("%s %s chunk %s %s => %s",
+		src.Network(),
+		c.flags.String(),
+		c.tag,
+		src.String(),
+		dst.String(),
+	)
+}
+
+func (c *chunkTCP) setSourceAddr(address string) error {
+	addr, err := net.ResolveTCPAddr("tcp", address)
+	if err != nil {
+		return err
+	}
+	c.sourceIP = addr.IP
+	c.sourcePort = addr.Port
+	return nil
+}
+
+func (c *chunkTCP) setDestinationAddr(address string) error {
+	addr, err := net.ResolveTCPAddr("tcp", address)
+	if err != nil {
+		return err
+	}
+	c.destinationIP = addr.IP
+	c.destinationPort = addr.Port
+	return nil
+}

vendor/github.com/pion/transport/vnet/chunk_queue.go

@@ -0,0 +1,65 @@
+package vnet
+
+import (
+	"sync"
+)
+
+type chunkQueue struct {
+	chunks       []Chunk
+	maxSize      int // 0 or negative value: unlimited
+	maxBytes     int // 0 or negative value: unlimited
+	currentBytes int
+	mutex        sync.RWMutex
+}
+
+func newChunkQueue(maxSize int, maxBytes int) *chunkQueue {
+	return &chunkQueue{
+		chunks:       []Chunk{},
+		maxSize:      maxSize,
+		maxBytes:     maxBytes,
+		currentBytes: 0,
+		mutex:        sync.RWMutex{},
+	}
+}
+
+func (q *chunkQueue) push(c Chunk) bool {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+
+	if q.maxSize > 0 && len(q.chunks) >= q.maxSize {
+		return false // dropped
+	}
+	if q.maxBytes > 0 && q.currentBytes+len(c.UserData()) >= q.maxBytes {
+		return false
+	}
+
+	q.currentBytes += len(c.UserData())
+	q.chunks = append(q.chunks, c)
+	return true
+}
+
+func (q *chunkQueue) pop() (Chunk, bool) {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+
+	if len(q.chunks) == 0 {
+		return nil, false
+	}
+
+	c := q.chunks[0]
+	q.chunks = q.chunks[1:]
+	q.currentBytes -= len(c.UserData())
+
+	return c, true
+}
+
+func (q *chunkQueue) peek() Chunk {
+	q.mutex.RLock()
+	defer q.mutex.RUnlock()
+
+	if len(q.chunks) == 0 {
+		return nil
+	}
+
+	return q.chunks[0]
+}

vendor/github.com/pion/transport/vnet/conn.go

@@ -0,0 +1,246 @@
+package vnet
+
+import (
+	"errors"
+	"io"
+	"math"
+	"net"
+	"sync"
+	"time"
+)
+
+const (
+	maxReadQueueSize = 1024
+)
+
+var (
+	errObsCannotBeNil       = errors.New("obs cannot be nil")
+	errUseClosedNetworkConn = errors.New("use of closed network connection")
+	errAddrNotUDPAddr       = errors.New("addr is not a net.UDPAddr")
+	errLocAddr              = errors.New("something went wrong with locAddr")
+	errAlreadyClosed        = errors.New("already closed")
+	errNoRemAddr            = errors.New("no remAddr defined")
+)
+
+// UDPPacketConn is packet-oriented connection for UDP.
+type UDPPacketConn interface {
+	net.PacketConn
+	Read(b []byte) (int, error)
+	RemoteAddr() net.Addr
+	Write(b []byte) (int, error)
+}
+
+// vNet implements this
+type connObserver interface {
+	write(c Chunk) error
+	onClosed(addr net.Addr)
+	determineSourceIP(locIP, dstIP net.IP) net.IP
+}
+
+// UDPConn is the implementation of the Conn and PacketConn interfaces for UDP network connections.
+// comatible with net.PacketConn and net.Conn
+type UDPConn struct {
+	locAddr   *net.UDPAddr // read-only
+	remAddr   *net.UDPAddr // read-only
+	obs       connObserver // read-only
+	readCh    chan Chunk   // thread-safe
+	closed    bool         // requires mutex
+	mu        sync.Mutex   // to mutex closed flag
+	readTimer *time.Timer  // thread-safe
+}
+
+func newUDPConn(locAddr, remAddr *net.UDPAddr, obs connObserver) (*UDPConn, error) {
+	if obs == nil {
+		return nil, errObsCannotBeNil
+	}
+
+	return &UDPConn{
+		locAddr:   locAddr,
+		remAddr:   remAddr,
+		obs:       obs,
+		readCh:    make(chan Chunk, maxReadQueueSize),
+		readTimer: time.NewTimer(time.Duration(math.MaxInt64)),
+	}, nil
+}
+
+// ReadFrom reads a packet from the connection,
+// copying the payload into p. It returns the number of
+// bytes copied into p and the return address that
+// was on the packet.
+// It returns the number of bytes read (0 <= n <= len(p))
+// and any error encountered. Callers should always process
+// the n > 0 bytes returned before considering the error err.
+// ReadFrom can be made to time out and return
+// an Error with Timeout() == true after a fixed time limit;
+// see SetDeadline and SetReadDeadline.
+func (c *UDPConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
+loop:
+	for {
+		select {
+		case chunk, ok := <-c.readCh:
+			if !ok {
+				break loop
+			}
+			var err error
+			n := copy(p, chunk.UserData())
+			addr := chunk.SourceAddr()
+			if n < len(chunk.UserData()) {
+				err = io.ErrShortBuffer
+			}
+
+			if c.remAddr != nil {
+				if addr.String() != c.remAddr.String() {
+					break // discard (shouldn't happen)
+				}
+			}
+			return n, addr, err
+
+		case <-c.readTimer.C:
+			return 0, nil, &net.OpError{
+				Op:   "read",
+				Net:  c.locAddr.Network(),
+				Addr: c.locAddr,
+				Err:  newTimeoutError("i/o timeout"),
+			}
+		}
+	}
+
+	return 0, nil, &net.OpError{
+		Op:   "read",
+		Net:  c.locAddr.Network(),
+		Addr: c.locAddr,
+		Err:  errUseClosedNetworkConn,
+	}
+}
+
+// WriteTo writes a packet with payload p to addr.
+// WriteTo can be made to time out and return
+// an Error with Timeout() == true after a fixed time limit;
+// see SetDeadline and SetWriteDeadline.
+// On packet-oriented connections, write timeouts are rare.
+func (c *UDPConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
+	dstAddr, ok := addr.(*net.UDPAddr)
+	if !ok {
+		return 0, errAddrNotUDPAddr
+	}
+
+	srcIP := c.obs.determineSourceIP(c.locAddr.IP, dstAddr.IP)
+	if srcIP == nil {
+		return 0, errLocAddr
+	}
+	srcAddr := &net.UDPAddr{
+		IP:   srcIP,
+		Port: c.locAddr.Port,
+	}
+
+	chunk := newChunkUDP(srcAddr, dstAddr)
+	chunk.userData = make([]byte, len(p))
+	copy(chunk.userData, p)
+	if err := c.obs.write(chunk); err != nil {
+		return 0, err
+	}
+	return len(p), nil
+}
+
+// Close closes the connection.
+// Any blocked ReadFrom or WriteTo operations will be unblocked and return errors.
+func (c *UDPConn) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.closed {
+		return errAlreadyClosed
+	}
+	c.closed = true
+	close(c.readCh)
+
+	c.obs.onClosed(c.locAddr)
+	return nil
+}
+
+// LocalAddr returns the local network address.
+func (c *UDPConn) LocalAddr() net.Addr {
+	return c.locAddr
+}
+
+// SetDeadline sets the read and write deadlines associated
+// with the connection. It is equivalent to calling both
+// SetReadDeadline and SetWriteDeadline.
+//
+// A deadline is an absolute time after which I/O operations
+// fail with a timeout (see type Error) instead of
+// blocking. The deadline applies to all future and pending
+// I/O, not just the immediately following call to ReadFrom or
+// WriteTo. After a deadline has been exceeded, the connection
+// can be refreshed by setting a deadline in the future.
+//
+// An idle timeout can be implemented by repeatedly extending
+// the deadline after successful ReadFrom or WriteTo calls.
+//
+// A zero value for t means I/O operations will not time out.
+func (c *UDPConn) SetDeadline(t time.Time) error {
+	return c.SetReadDeadline(t)
+}
+
+// SetReadDeadline sets the deadline for future ReadFrom calls
+// and any currently-blocked ReadFrom call.
+// A zero value for t means ReadFrom will not time out.
+func (c *UDPConn) SetReadDeadline(t time.Time) error {
+	var d time.Duration
+	var noDeadline time.Time
+	if t == noDeadline {
+		d = time.Duration(math.MaxInt64)
+	} else {
+		d = time.Until(t)
+	}
+	c.readTimer.Reset(d)
+	return nil
+}
+
+// SetWriteDeadline sets the deadline for future WriteTo calls
+// and any currently-blocked WriteTo call.
+// Even if write times out, it may return n > 0, indicating that
+// some of the data was successfully written.
+// A zero value for t means WriteTo will not time out.
+func (c *UDPConn) SetWriteDeadline(t time.Time) error {
+	// Write never blocks.
+	return nil
+}
+
+// Read reads data from the connection.
+// Read can be made to time out and return an Error with Timeout() == true
+// after a fixed time limit; see SetDeadline and SetReadDeadline.
+func (c *UDPConn) Read(b []byte) (int, error) {
+	n, _, err := c.ReadFrom(b)
+	return n, err
+}
+
+// RemoteAddr returns the remote network address.
+func (c *UDPConn) RemoteAddr() net.Addr {
+	return c.remAddr
+}
+
+// Write writes data to the connection.
+// Write can be made to time out and return an Error with Timeout() == true
+// after a fixed time limit; see SetDeadline and SetWriteDeadline.
+func (c *UDPConn) Write(b []byte) (int, error) {
+	if c.remAddr == nil {
+		return 0, errNoRemAddr
+	}
+
+	return c.WriteTo(b, c.remAddr)
+}
+
+func (c *UDPConn) onInboundChunk(chunk Chunk) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.closed {
+		return
+	}
+
+	select {
+	case c.readCh <- chunk:
+	default:
+	}
+}

vendor/github.com/pion/transport/vnet/conn_map.go

@@ -0,0 +1,136 @@
+package vnet
+
+import (
+	"errors"
+	"net"
+	"sync"
+)
+
+var (
+	errAddressAlreadyInUse       = errors.New("address already in use")
+	errNoSuchUDPConn             = errors.New("no such UDPConn")
+	errCannotRemoveUnspecifiedIP = errors.New("cannot remove unspecified IP by the specified IP")
+)
+
+type udpConnMap struct {
+	portMap map[int][]*UDPConn
+	mutex   sync.RWMutex
+}
+
+func newUDPConnMap() *udpConnMap {
+	return &udpConnMap{
+		portMap: map[int][]*UDPConn{},
+	}
+}
+
+func (m *udpConnMap) insert(conn *UDPConn) error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	udpAddr := conn.LocalAddr().(*net.UDPAddr)
+
+	// check if the port has a listener
+	conns, ok := m.portMap[udpAddr.Port]
+	if ok {
+		if udpAddr.IP.IsUnspecified() {
+			return errAddressAlreadyInUse
+		}
+
+		for _, conn := range conns {
+			laddr := conn.LocalAddr().(*net.UDPAddr)
+			if laddr.IP.IsUnspecified() || laddr.IP.Equal(udpAddr.IP) {
+				return errAddressAlreadyInUse
+			}
+		}
+
+		conns = append(conns, conn)
+	} else {
+		conns = []*UDPConn{conn}
+	}
+
+	m.portMap[udpAddr.Port] = conns
+	return nil
+}
+
+func (m *udpConnMap) find(addr net.Addr) (*UDPConn, bool) {
+	m.mutex.Lock() // could be RLock, but we have delete() op
+	defer m.mutex.Unlock()
+
+	udpAddr := addr.(*net.UDPAddr)
+
+	if conns, ok := m.portMap[udpAddr.Port]; ok {
+		if udpAddr.IP.IsUnspecified() {
+			// pick the first one appears in the iteration
+			if len(conns) == 0 {
+				// This can't happen!
+				delete(m.portMap, udpAddr.Port)
+				return nil, false
+			}
+			return conns[0], true
+		}
+
+		for _, conn := range conns {
+			laddr := conn.LocalAddr().(*net.UDPAddr)
+			if laddr.IP.IsUnspecified() || laddr.IP.Equal(udpAddr.IP) {
+				return conn, ok
+			}
+		}
+	}
+
+	return nil, false
+}
+
+func (m *udpConnMap) delete(addr net.Addr) error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	udpAddr := addr.(*net.UDPAddr)
+
+	conns, ok := m.portMap[udpAddr.Port]
+	if !ok {
+		return errNoSuchUDPConn
+	}
+
+	if udpAddr.IP.IsUnspecified() {
+		// remove all from this port
+		delete(m.portMap, udpAddr.Port)
+		return nil
+	}
+
+	newConns := []*UDPConn{}
+
+	for _, conn := range conns {
+		laddr := conn.LocalAddr().(*net.UDPAddr)
+		if laddr.IP.IsUnspecified() {
+			// This can't happen!
+			return errCannotRemoveUnspecifiedIP
+		}
+
+		if laddr.IP.Equal(udpAddr.IP) {
+			continue
+		}
+
+		newConns = append(newConns, conn)
+	}
+
+	if len(newConns) == 0 {
+		delete(m.portMap, udpAddr.Port)
+	} else {
+		m.portMap[udpAddr.Port] = newConns
+	}
+
+	return nil
+}
+
+// size returns the number of UDPConns (UDP listeners)
+func (m *udpConnMap) size() int {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+
+	n := 0
+	for _, conns := range m.portMap {
+		n += len(conns)
+	}
+
+	return n
+}

vendor/github.com/pion/transport/vnet/delay_filter.go

@@ -0,0 +1,75 @@
+package vnet
+
+import (
+	"context"
+	"time"
+)
+
+// DelayFilter delays outgoing packets by the given delay. Run must be called
+// before any packets will be forwarded.
+type DelayFilter struct {
+	NIC
+	delay time.Duration
+	push  chan struct{}
+	queue *chunkQueue
+}
+
+type timedChunk struct {
+	Chunk
+	deadline time.Time
+}
+
+// NewDelayFilter creates a new DelayFilter with the given nic and delay.
+func NewDelayFilter(nic NIC, delay time.Duration) (*DelayFilter, error) {
+	return &DelayFilter{
+		NIC:   nic,
+		delay: delay,
+		push:  make(chan struct{}),
+		queue: newChunkQueue(0, 0),
+	}, nil
+}
+
+func (f *DelayFilter) onInboundChunk(c Chunk) {
+	f.queue.push(timedChunk{
+		Chunk:    c,
+		deadline: time.Now().Add(f.delay),
+	})
+	f.push <- struct{}{}
+}
+
+// Run starts forwarding of packets. Packets will be forwarded if they spent
+// >delay time in the internal queue. Must be called before any packet will be
+// forwarded.
+func (f *DelayFilter) Run(ctx context.Context) {
+	timer := time.NewTimer(0)
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-f.push:
+			next := f.queue.peek().(timedChunk)
+			if !timer.Stop() {
+				<-timer.C
+			}
+			timer.Reset(time.Until(next.deadline))
+		case now := <-timer.C:
+			next := f.queue.peek()
+			if next == nil {
+				timer.Reset(time.Minute)
+				continue
+			}
+			if n, ok := next.(timedChunk); ok && n.deadline.Before(now) {
+				f.queue.pop() // ignore result because we already got and casted it from peek
+				f.NIC.onInboundChunk(n.Chunk)
+			}
+			next = f.queue.peek()
+			if next == nil {
+				timer.Reset(time.Minute)
+				continue
+			}
+			if n, ok := next.(timedChunk); ok {
+				timer.Reset(time.Until(n.deadline))
+			}
+		}
+	}
+}

vendor/github.com/pion/transport/vnet/errors.go

@@ -0,0 +1,19 @@
+package vnet
+
+type timeoutError struct {
+	msg string
+}
+
+func newTimeoutError(msg string) error {
+	return &timeoutError{
+		msg: msg,
+	}
+}
+
+func (e *timeoutError) Error() string {
+	return e.msg
+}
+
+func (e *timeoutError) Timeout() bool {
+	return true
+}

vendor/github.com/pion/transport/vnet/interface.go

@@ -0,0 +1,40 @@
+package vnet
+
+import (
+	"errors"
+	"net"
+)
+
+var errNoAddressAssigned = errors.New("no address assigned")
+
+// See: https://play.golang.org/p/nBO9KGYEziv
+
+// InterfaceBase ...
+type InterfaceBase net.Interface
+
+// Interface ...
+type Interface struct {
+	InterfaceBase
+	addrs []net.Addr
+}
+
+// NewInterface ...
+func NewInterface(ifc net.Interface) *Interface {
+	return &Interface{
+		InterfaceBase: InterfaceBase(ifc),
+		addrs:         nil,
+	}
+}
+
+// AddAddr ...
+func (ifc *Interface) AddAddr(addr net.Addr) {
+	ifc.addrs = append(ifc.addrs, addr)
+}
+
+// Addrs ...
+func (ifc *Interface) Addrs() ([]net.Addr, error) {
+	if len(ifc.addrs) == 0 {
+		return nil, errNoAddressAssigned
+	}
+	return ifc.addrs, nil
+}

vendor/github.com/pion/transport/vnet/loss_filter.go

@@ -0,0 +1,33 @@
+package vnet
+
+import (
+	"math/rand"
+	"time"
+)
+
+// LossFilter is a wrapper around NICs, that drops some of the packets passed to
+// onInboundChunk
+type LossFilter struct {
+	NIC
+	chance int
+}
+
+// NewLossFilter creates a new LossFilter that drops every packet with a
+// probability of chance/100. Every packet that is not dropped is passed on to
+// the given NIC.
+func NewLossFilter(nic NIC, chance int) (*LossFilter, error) {
+	f := &LossFilter{
+		NIC:    nic,
+		chance: chance,
+	}
+	rand.Seed(time.Now().UTC().UnixNano())
+	return f, nil
+}
+
+func (f *LossFilter) onInboundChunk(c Chunk) {
+	if rand.Intn(100) < f.chance { //nolint:gosec
+		return
+	}
+
+	f.NIC.onInboundChunk(c)
+}

vendor/github.com/pion/transport/vnet/nat.go

@@ -0,0 +1,338 @@
+package vnet
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/pion/logging"
+)
+
+var (
+	errNATRequriesMapping            = errors.New("1:1 NAT requires more than one mapping")
+	errMismatchLengthIP              = errors.New("length mismtach between mappedIPs and localIPs")
+	errNonUDPTranslationNotSupported = errors.New("non-udp translation is not supported yet")
+	errNoAssociatedLocalAddress      = errors.New("no associated local address")
+	errNoNATBindingFound             = errors.New("no NAT binding found")
+	errHasNoPermission               = errors.New("has no permission")
+)
+
+// EndpointDependencyType defines a type of behavioral dependendency on the
+// remote endpoint's IP address or port number. This is used for the two
+// kinds of behaviors:
+//  - Port mapping behavior
+//  - Filtering behavior
+// See: https://tools.ietf.org/html/rfc4787
+type EndpointDependencyType uint8
+
+const (
+	// EndpointIndependent means the behavior is independent of the endpoint's address or port
+	EndpointIndependent EndpointDependencyType = iota
+	// EndpointAddrDependent means the behavior is dependent on the endpoint's address
+	EndpointAddrDependent
+	// EndpointAddrPortDependent means the behavior is dependent on the endpoint's address and port
+	EndpointAddrPortDependent
+)
+
+// NATMode defines basic behavior of the NAT
+type NATMode uint8
+
+const (
+	// NATModeNormal means the NAT behaves as a standard NAPT (RFC 2663).
+	NATModeNormal NATMode = iota
+	// NATModeNAT1To1 exhibits 1:1 DNAT where the external IP address is statically mapped to
+	// a specific local IP address with port number is preserved always between them.
+	// When this mode is selected, MappingBehavior, FilteringBehavior, PortPreservation and
+	// MappingLifeTime of NATType are ignored.
+	NATModeNAT1To1
+)
+
+const (
+	defaultNATMappingLifeTime = 30 * time.Second
+)
+
+// NATType has a set of parameters that define the behavior of NAT.
+type NATType struct {
+	Mode              NATMode
+	MappingBehavior   EndpointDependencyType
+	FilteringBehavior EndpointDependencyType
+	Hairpining        bool // Not implemented yet
+	PortPreservation  bool // Not implemented yet
+	MappingLifeTime   time.Duration
+}
+
+type natConfig struct {
+	name          string
+	natType       NATType
+	mappedIPs     []net.IP // mapped IPv4
+	localIPs      []net.IP // local IPv4, required only when the mode is NATModeNAT1To1
+	loggerFactory logging.LoggerFactory
+}
+
+type mapping struct {
+	proto   string              // "udp" or "tcp"
+	local   string              // "<local-ip>:<local-port>"
+	mapped  string              // "<mapped-ip>:<mapped-port>"
+	bound   string              // key: "[<remote-ip>[:<remote-port>]]"
+	filters map[string]struct{} // key: "[<remote-ip>[:<remote-port>]]"
+	expires time.Time           // time to expire
+}
+
+type networkAddressTranslator struct {
+	name           string
+	natType        NATType
+	mappedIPs      []net.IP            // mapped IPv4
+	localIPs       []net.IP            // local IPv4, required only when the mode is NATModeNAT1To1
+	outboundMap    map[string]*mapping // key: "<proto>:<local-ip>:<local-port>[:remote-ip[:remote-port]]
+	inboundMap     map[string]*mapping // key: "<proto>:<mapped-ip>:<mapped-port>"
+	udpPortCounter int
+	mutex          sync.RWMutex
+	log            logging.LeveledLogger
+}
+
+func newNAT(config *natConfig) (*networkAddressTranslator, error) {
+	natType := config.natType
+
+	if natType.Mode == NATModeNAT1To1 {
+		// 1:1 NAT behavior
+		natType.MappingBehavior = EndpointIndependent
+		natType.FilteringBehavior = EndpointIndependent
+		natType.PortPreservation = true
+		natType.MappingLifeTime = 0
+
+		if len(config.mappedIPs) == 0 {
+			return nil, errNATRequriesMapping
+		}
+		if len(config.mappedIPs) != len(config.localIPs) {
+			return nil, errMismatchLengthIP
+		}
+	} else {
+		// Normal (NAPT) behavior
+		natType.Mode = NATModeNormal
+		if natType.MappingLifeTime == 0 {
+			natType.MappingLifeTime = defaultNATMappingLifeTime
+		}
+	}
+
+	return &networkAddressTranslator{
+		name:        config.name,
+		natType:     natType,
+		mappedIPs:   config.mappedIPs,
+		localIPs:    config.localIPs,
+		outboundMap: map[string]*mapping{},
+		inboundMap:  map[string]*mapping{},
+		log:         config.loggerFactory.NewLogger("vnet"),
+	}, nil
+}
+
+func (n *networkAddressTranslator) getPairedMappedIP(locIP net.IP) net.IP {
+	for i, ip := range n.localIPs {
+		if ip.Equal(locIP) {
+			return n.mappedIPs[i]
+		}
+	}
+	return nil
+}
+
+func (n *networkAddressTranslator) getPairedLocalIP(mappedIP net.IP) net.IP {
+	for i, ip := range n.mappedIPs {
+		if ip.Equal(mappedIP) {
+			return n.localIPs[i]
+		}
+	}
+	return nil
+}
+
+func (n *networkAddressTranslator) translateOutbound(from Chunk) (Chunk, error) {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	to := from.Clone()
+
+	if from.Network() == udpString {
+		if n.natType.Mode == NATModeNAT1To1 {
+			// 1:1 NAT behavior
+			srcAddr := from.SourceAddr().(*net.UDPAddr)
+			srcIP := n.getPairedMappedIP(srcAddr.IP)
+			if srcIP == nil {
+				n.log.Debugf("[%s] drop outbound chunk %s with not route", n.name, from.String())
+				return nil, nil // silently discard
+			}
+			srcPort := srcAddr.Port
+			if err := to.setSourceAddr(fmt.Sprintf("%s:%d", srcIP.String(), srcPort)); err != nil {
+				return nil, err
+			}
+		} else {
+			// Normal (NAPT) behavior
+			var bound, filterKey string
+			switch n.natType.MappingBehavior {
+			case EndpointIndependent:
+				bound = ""
+			case EndpointAddrDependent:
+				bound = from.getDestinationIP().String()
+			case EndpointAddrPortDependent:
+				bound = from.DestinationAddr().String()
+			}
+
+			switch n.natType.FilteringBehavior {
+			case EndpointIndependent:
+				filterKey = ""
+			case EndpointAddrDependent:
+				filterKey = from.getDestinationIP().String()
+			case EndpointAddrPortDependent:
+				filterKey = from.DestinationAddr().String()
+			}
+
+			oKey := fmt.Sprintf("udp:%s:%s", from.SourceAddr().String(), bound)
+
+			m := n.findOutboundMapping(oKey)
+			if m == nil {
+				// Create a new mapping
+				mappedPort := 0xC000 + n.udpPortCounter
+				n.udpPortCounter++
+
+				m = &mapping{
+					proto:   from.SourceAddr().Network(),
+					local:   from.SourceAddr().String(),
+					bound:   bound,
+					mapped:  fmt.Sprintf("%s:%d", n.mappedIPs[0].String(), mappedPort),
+					filters: map[string]struct{}{},
+					expires: time.Now().Add(n.natType.MappingLifeTime),
+				}
+
+				n.outboundMap[oKey] = m
+
+				iKey := fmt.Sprintf("udp:%s", m.mapped)
+
+				n.log.Debugf("[%s] created a new NAT binding oKey=%s iKey=%s\n",
+					n.name,
+					oKey,
+					iKey)
+
+				m.filters[filterKey] = struct{}{}
+				n.log.Debugf("[%s] permit access from %s to %s\n", n.name, filterKey, m.mapped)
+				n.inboundMap[iKey] = m
+			} else if _, ok := m.filters[filterKey]; !ok {
+				n.log.Debugf("[%s] permit access from %s to %s\n", n.name, filterKey, m.mapped)
+				m.filters[filterKey] = struct{}{}
+			}
+
+			if err := to.setSourceAddr(m.mapped); err != nil {
+				return nil, err
+			}
+		}
+
+		n.log.Debugf("[%s] translate outbound chunk from %s to %s", n.name, from.String(), to.String())
+
+		return to, nil
+	}
+
+	return nil, errNonUDPTranslationNotSupported
+}
+
+func (n *networkAddressTranslator) translateInbound(from Chunk) (Chunk, error) {
+	n.mutex.Lock()
+	defer n.mutex.Unlock()
+
+	to := from.Clone()
+
+	if from.Network() == udpString {
+		if n.natType.Mode == NATModeNAT1To1 {
+			// 1:1 NAT behavior
+			dstAddr := from.DestinationAddr().(*net.UDPAddr)
+			dstIP := n.getPairedLocalIP(dstAddr.IP)
+			if dstIP == nil {
+				return nil, fmt.Errorf("drop %s as %w", from.String(), errNoAssociatedLocalAddress)
+			}
+			dstPort := from.DestinationAddr().(*net.UDPAddr).Port
+			if err := to.setDestinationAddr(fmt.Sprintf("%s:%d", dstIP, dstPort)); err != nil {
+				return nil, err
+			}
+		} else {
+			// Normal (NAPT) behavior
+			iKey := fmt.Sprintf("udp:%s", from.DestinationAddr().String())
+			m := n.findInboundMapping(iKey)
+			if m == nil {
+				return nil, fmt.Errorf("drop %s as %w", from.String(), errNoNATBindingFound)
+			}
+
+			var filterKey string
+			switch n.natType.FilteringBehavior {
+			case EndpointIndependent:
+				filterKey = ""
+			case EndpointAddrDependent:
+				filterKey = from.getSourceIP().String()
+			case EndpointAddrPortDependent:
+				filterKey = from.SourceAddr().String()
+			}
+
+			if _, ok := m.filters[filterKey]; !ok {
+				return nil, fmt.Errorf("drop %s as the remote %s %w", from.String(), filterKey, errHasNoPermission)
+			}
+
+			// See RFC 4847 Section 4.3.  Mapping Refresh
+			// a) Inbound refresh may be useful for applications with no outgoing
+			//   UDP traffic.  However, allowing inbound refresh may allow an
+			//   external attacker or misbehaving application to keep a mapping
+			//   alive indefinitely.  This may be a security risk.  Also, if the
+			//   process is repeated with different ports, over time, it could
+			//   use up all the ports on the NAT.
+
+			if err := to.setDestinationAddr(m.local); err != nil {
+				return nil, err
+			}
+		}
+
+		n.log.Debugf("[%s] translate inbound chunk from %s to %s", n.name, from.String(), to.String())
+
+		return to, nil
+	}
+
+	return nil, errNonUDPTranslationNotSupported
+}
+
+// caller must hold the mutex
+func (n *networkAddressTranslator) findOutboundMapping(oKey string) *mapping {
+	now := time.Now()
+
+	m, ok := n.outboundMap[oKey]
+	if ok {
+		// check if this mapping is expired
+		if now.After(m.expires) {
+			n.removeMapping(m)
+			m = nil // expired
+		} else {
+			m.expires = time.Now().Add(n.natType.MappingLifeTime)
+		}
+	}
+
+	return m
+}
+
+// caller must hold the mutex
+func (n *networkAddressTranslator) findInboundMapping(iKey string) *mapping {
+	now := time.Now()
+	m, ok := n.inboundMap[iKey]
+	if !ok {
+		return nil
+	}
+
+	// check if this mapping is expired
+	if now.After(m.expires) {
+		n.removeMapping(m)
+		return nil
+	}
+
+	return m
+}
+
+// caller must hold the mutex
+func (n *networkAddressTranslator) removeMapping(m *mapping) {
+	oKey := fmt.Sprintf("%s:%s:%s", m.proto, m.local, m.bound)
+	iKey := fmt.Sprintf("%s:%s", m.proto, m.mapped)
+
+	delete(n.outboundMap, oKey)
+	delete(n.inboundMap, iKey)
+}

vendor/github.com/pion/transport/vnet/net.go

@@ -0,0 +1,677 @@
+package vnet
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"math/rand"
+	"net"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const (
+	lo0String = "lo0String"
+	udpString = "udp"
+)
+
+var (
+	macAddrCounter                 uint64 = 0xBEEFED910200 //nolint:gochecknoglobals
+	errNoInterface                        = errors.New("no interface is available")
+	errNotFound                           = errors.New("not found")
+	errUnexpectedNetwork                  = errors.New("unexpected network")
+	errCantAssignRequestedAddr            = errors.New("can't assign requested address")
+	errUnknownNetwork                     = errors.New("unknown network")
+	errNoRouterLinked                     = errors.New("no router linked")
+	errInvalidPortNumber                  = errors.New("invalid port number")
+	errUnexpectedTypeSwitchFailure        = errors.New("unexpected type-switch failure")
+	errBindFailerFor                      = errors.New("bind failed for")
+	errEndPortLessThanStart               = errors.New("end port is less than the start")
+	errPortSpaceExhausted                 = errors.New("port space exhausted")
+	errVNetDisabled                       = errors.New("vnet is not enabled")
+)
+
+func newMACAddress() net.HardwareAddr {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, macAddrCounter)
+	macAddrCounter++
+	return b[2:]
+}
+
+type vNet struct {
+	interfaces []*Interface // read-only
+	staticIPs  []net.IP     // read-only
+	router     *Router      // read-only
+	udpConns   *udpConnMap  // read-only
+	mutex      sync.RWMutex
+}
+
+func (v *vNet) _getInterfaces() ([]*Interface, error) {
+	if len(v.interfaces) == 0 {
+		return nil, errNoInterface
+	}
+
+	return v.interfaces, nil
+}
+
+func (v *vNet) getInterfaces() ([]*Interface, error) {
+	v.mutex.RLock()
+	defer v.mutex.RUnlock()
+
+	return v._getInterfaces()
+}
+
+// caller must hold the mutex (read)
+func (v *vNet) _getInterface(ifName string) (*Interface, error) {
+	ifs, err := v._getInterfaces()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifc := range ifs {
+		if ifc.Name == ifName {
+			return ifc, nil
+		}
+	}
+
+	return nil, fmt.Errorf("interface %s %w", ifName, errNotFound)
+}
+
+func (v *vNet) getInterface(ifName string) (*Interface, error) {
+	v.mutex.RLock()
+	defer v.mutex.RUnlock()
+
+	return v._getInterface(ifName)
+}
+
+// caller must hold the mutex
+func (v *vNet) getAllIPAddrs(ipv6 bool) []net.IP {
+	ips := []net.IP{}
+
+	for _, ifc := range v.interfaces {
+		addrs, err := ifc.Addrs()
+		if err != nil {
+			continue
+		}
+
+		for _, addr := range addrs {
+			var ip net.IP
+			if ipNet, ok := addr.(*net.IPNet); ok {
+				ip = ipNet.IP
+			} else if ipAddr, ok := addr.(*net.IPAddr); ok {
+				ip = ipAddr.IP
+			} else {
+				continue
+			}
+
+			if !ipv6 {
+				if ip.To4() != nil {
+					ips = append(ips, ip)
+				}
+			}
+		}
+	}
+
+	return ips
+}
+
+func (v *vNet) setRouter(r *Router) error {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	v.router = r
+	return nil
+}
+
+func (v *vNet) onInboundChunk(c Chunk) {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	if c.Network() == udpString {
+		if conn, ok := v.udpConns.find(c.DestinationAddr()); ok {
+			conn.onInboundChunk(c)
+		}
+	}
+}
+
+// caller must hold the mutex
+func (v *vNet) _dialUDP(network string, locAddr, remAddr *net.UDPAddr) (UDPPacketConn, error) {
+	// validate network
+	if network != udpString && network != "udp4" {
+		return nil, fmt.Errorf("%w: %s", errUnexpectedNetwork, network)
+	}
+
+	if locAddr == nil {
+		locAddr = &net.UDPAddr{
+			IP: net.IPv4zero,
+		}
+	} else if locAddr.IP == nil {
+		locAddr.IP = net.IPv4zero
+	}
+
+	// validate address. do we have that address?
+	if !v.hasIPAddr(locAddr.IP) {
+		return nil, &net.OpError{
+			Op:   "listen",
+			Net:  network,
+			Addr: locAddr,
+			Err:  fmt.Errorf("bind: %w", errCantAssignRequestedAddr),
+		}
+	}
+
+	if locAddr.Port == 0 {
+		// choose randomly from the range between 5000 and 5999
+		port, err := v.assignPort(locAddr.IP, 5000, 5999)
+		if err != nil {
+			return nil, &net.OpError{
+				Op:   "listen",
+				Net:  network,
+				Addr: locAddr,
+				Err:  err,
+			}
+		}
+		locAddr.Port = port
+	} else if _, ok := v.udpConns.find(locAddr); ok {
+		return nil, &net.OpError{
+			Op:   "listen",
+			Net:  network,
+			Addr: locAddr,
+			Err:  fmt.Errorf("bind: %w", errAddressAlreadyInUse),
+		}
+	}
+
+	conn, err := newUDPConn(locAddr, remAddr, v)
+	if err != nil {
+		return nil, err
+	}
+
+	err = v.udpConns.insert(conn)
+	if err != nil {
+		return nil, err
+	}
+
+	return conn, nil
+}
+
+func (v *vNet) listenPacket(network string, address string) (UDPPacketConn, error) {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	locAddr, err := v.resolveUDPAddr(network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	return v._dialUDP(network, locAddr, nil)
+}
+
+func (v *vNet) listenUDP(network string, locAddr *net.UDPAddr) (UDPPacketConn, error) {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	return v._dialUDP(network, locAddr, nil)
+}
+
+func (v *vNet) dialUDP(network string, locAddr, remAddr *net.UDPAddr) (UDPPacketConn, error) {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	return v._dialUDP(network, locAddr, remAddr)
+}
+
+func (v *vNet) dial(network string, address string) (UDPPacketConn, error) {
+	v.mutex.Lock()
+	defer v.mutex.Unlock()
+
+	remAddr, err := v.resolveUDPAddr(network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	// Determine source address
+	srcIP := v.determineSourceIP(nil, remAddr.IP)
+
+	locAddr := &net.UDPAddr{IP: srcIP, Port: 0}
+
+	return v._dialUDP(network, locAddr, remAddr)
+}
+
+func (v *vNet) resolveUDPAddr(network, address string) (*net.UDPAddr, error) {
+	if network != udpString && network != "udp4" {
+		return nil, fmt.Errorf("%w %s", errUnknownNetwork, network)
+	}
+
+	host, sPort, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+
+	// Check if host is a domain name
+	ip := net.ParseIP(host)
+	if ip == nil {
+		host = strings.ToLower(host)
+		if host == "localhost" {
+			ip = net.IPv4(127, 0, 0, 1)
+		} else {
+			// host is a domain name. resolve IP address by the name
+			if v.router == nil {
+				return nil, errNoRouterLinked
+			}
+
+			ip, err = v.router.resolver.lookUp(host)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	port, err := strconv.Atoi(sPort)
+	if err != nil {
+		return nil, errInvalidPortNumber
+	}
+
+	udpAddr := &net.UDPAddr{
+		IP:   ip,
+		Port: port,
+	}
+
+	return udpAddr, nil
+}
+
+func (v *vNet) write(c Chunk) error {
+	if c.Network() == udpString {
+		if udp, ok := c.(*chunkUDP); ok {
+			if c.getDestinationIP().IsLoopback() {
+				if conn, ok := v.udpConns.find(udp.DestinationAddr()); ok {
+					conn.onInboundChunk(udp)
+				}
+				return nil
+			}
+		} else {
+			return errUnexpectedTypeSwitchFailure
+		}
+	}
+
+	if v.router == nil {
+		return errNoRouterLinked
+	}
+
+	v.router.push(c)
+	return nil
+}
+
+func (v *vNet) onClosed(addr net.Addr) {
+	if addr.Network() == udpString {
+		//nolint:errcheck
+		v.udpConns.delete(addr) // #nosec
+	}
+}
+
+// This method determines the srcIP based on the dstIP when locIP
+// is any IP address ("0.0.0.0" or "::"). If locIP is a non-any addr,
+// this method simply returns locIP.
+// caller must hold the mutex
+func (v *vNet) determineSourceIP(locIP, dstIP net.IP) net.IP {
+	if locIP != nil && !locIP.IsUnspecified() {
+		return locIP
+	}
+
+	var srcIP net.IP
+
+	if dstIP.IsLoopback() {
+		srcIP = net.ParseIP("127.0.0.1")
+	} else {
+		ifc, err2 := v._getInterface("eth0")
+		if err2 != nil {
+			return nil
+		}
+
+		addrs, err2 := ifc.Addrs()
+		if err2 != nil {
+			return nil
+		}
+
+		if len(addrs) == 0 {
+			return nil
+		}
+
+		var findIPv4 bool
+		if locIP != nil {
+			findIPv4 = (locIP.To4() != nil)
+		} else {
+			findIPv4 = (dstIP.To4() != nil)
+		}
+
+		for _, addr := range addrs {
+			ip := addr.(*net.IPNet).IP
+			if findIPv4 {
+				if ip.To4() != nil {
+					srcIP = ip
+					break
+				}
+			} else {
+				if ip.To4() == nil {
+					srcIP = ip
+					break
+				}
+			}
+		}
+	}
+
+	return srcIP
+}
+
+// caller must hold the mutex
+func (v *vNet) hasIPAddr(ip net.IP) bool { //nolint:gocognit
+	for _, ifc := range v.interfaces {
+		if addrs, err := ifc.Addrs(); err == nil {
+			for _, addr := range addrs {
+				var locIP net.IP
+				if ipNet, ok := addr.(*net.IPNet); ok {
+					locIP = ipNet.IP
+				} else if ipAddr, ok := addr.(*net.IPAddr); ok {
+					locIP = ipAddr.IP
+				} else {
+					continue
+				}
+
+				switch ip.String() {
+				case "0.0.0.0":
+					if locIP.To4() != nil {
+						return true
+					}
+				case "::":
+					if locIP.To4() == nil {
+						return true
+					}
+				default:
+					if locIP.Equal(ip) {
+						return true
+					}
+				}
+			}
+		}
+	}
+
+	return false
+}
+
+// caller must hold the mutex
+func (v *vNet) allocateLocalAddr(ip net.IP, port int) error {
+	// gather local IP addresses to bind
+	var ips []net.IP
+	if ip.IsUnspecified() {
+		ips = v.getAllIPAddrs(ip.To4() == nil)
+	} else if v.hasIPAddr(ip) {
+		ips = []net.IP{ip}
+	}
+
+	if len(ips) == 0 {
+		return fmt.Errorf("%w %s", errBindFailerFor, ip.String())
+	}
+
+	// check if all these transport addresses are not in use
+	for _, ip2 := range ips {
+		addr := &net.UDPAddr{
+			IP:   ip2,
+			Port: port,
+		}
+		if _, ok := v.udpConns.find(addr); ok {
+			return &net.OpError{
+				Op:   "bind",
+				Net:  udpString,
+				Addr: addr,
+				Err:  fmt.Errorf("bind: %w", errAddressAlreadyInUse),
+			}
+		}
+	}
+
+	return nil
+}
+
+// caller must hold the mutex
+func (v *vNet) assignPort(ip net.IP, start, end int) (int, error) {
+	// choose randomly from the range between start and end (inclusive)
+	if end < start {
+		return -1, errEndPortLessThanStart
+	}
+
+	space := end + 1 - start
+	offset := rand.Intn(space) //nolint:gosec
+	for i := 0; i < space; i++ {
+		port := ((offset + i) % space) + start
+
+		err := v.allocateLocalAddr(ip, port)
+		if err == nil {
+			return port, nil
+		}
+	}
+
+	return -1, errPortSpaceExhausted
+}
+
+// NetConfig is a bag of configuration parameters passed to NewNet().
+type NetConfig struct {
+	// StaticIPs is an array of static IP addresses to be assigned for this Net.
+	// If no static IP address is given, the router will automatically assign
+	// an IP address.
+	StaticIPs []string
+
+	// StaticIP is deprecated. Use StaticIPs.
+	StaticIP string
+}
+
+// Net represents a local network stack euivalent to a set of layers from NIC
+// up to the transport (UDP / TCP) layer.
+type Net struct {
+	v   *vNet
+	ifs []*Interface
+}
+
+// NewNet creates an instance of Net.
+// If config is nil, the virtual network is disabled. (uses corresponding
+// net.Xxxx() operations.
+// By design, it always have lo0 and eth0 interfaces.
+// The lo0 has the address 127.0.0.1 assigned by default.
+// IP address for eth0 will be assigned when this Net is added to a router.
+func NewNet(config *NetConfig) *Net {
+	if config == nil {
+		ifs := []*Interface{}
+		if orgIfs, err := net.Interfaces(); err == nil {
+			for _, orgIfc := range orgIfs {
+				ifc := NewInterface(orgIfc)
+				if addrs, err := orgIfc.Addrs(); err == nil {
+					for _, addr := range addrs {
+						ifc.AddAddr(addr)
+					}
+				}
+
+				ifs = append(ifs, ifc)
+			}
+		}
+
+		return &Net{ifs: ifs}
+	}
+
+	lo0 := NewInterface(net.Interface{
+		Index:        1,
+		MTU:          16384,
+		Name:         lo0String,
+		HardwareAddr: nil,
+		Flags:        net.FlagUp | net.FlagLoopback | net.FlagMulticast,
+	})
+	lo0.AddAddr(&net.IPNet{
+		IP:   net.ParseIP("127.0.0.1"),
+		Mask: net.CIDRMask(8, 32),
+	})
+
+	eth0 := NewInterface(net.Interface{
+		Index:        2,
+		MTU:          1500,
+		Name:         "eth0",
+		HardwareAddr: newMACAddress(),
+		Flags:        net.FlagUp | net.FlagMulticast,
+	})
+
+	var staticIPs []net.IP
+	for _, ipStr := range config.StaticIPs {
+		if ip := net.ParseIP(ipStr); ip != nil {
+			staticIPs = append(staticIPs, ip)
+		}
+	}
+	if len(config.StaticIP) > 0 {
+		if ip := net.ParseIP(config.StaticIP); ip != nil {
+			staticIPs = append(staticIPs, ip)
+		}
+	}
+
+	v := &vNet{
+		interfaces: []*Interface{lo0, eth0},
+		staticIPs:  staticIPs,
+		udpConns:   newUDPConnMap(),
+	}
+
+	return &Net{
+		v: v,
+	}
+}
+
+// Interfaces returns a list of the system's network interfaces.
+func (n *Net) Interfaces() ([]*Interface, error) {
+	if n.v == nil {
+		return n.ifs, nil
+	}
+
+	return n.v.getInterfaces()
+}
+
+// InterfaceByName returns the interface specified by name.
+func (n *Net) InterfaceByName(name string) (*Interface, error) {
+	if n.v == nil {
+		for _, ifc := range n.ifs {
+			if ifc.Name == name {
+				return ifc, nil
+			}
+		}
+
+		return nil, fmt.Errorf("interface %s %w", name, errNotFound)
+	}
+
+	return n.v.getInterface(name)
+}
+
+// ListenPacket announces on the local network address.
+func (n *Net) ListenPacket(network string, address string) (net.PacketConn, error) {
+	if n.v == nil {
+		return net.ListenPacket(network, address)
+	}
+
+	return n.v.listenPacket(network, address)
+}
+
+// ListenUDP acts like ListenPacket for UDP networks.
+func (n *Net) ListenUDP(network string, locAddr *net.UDPAddr) (UDPPacketConn, error) {
+	if n.v == nil {
+		return net.ListenUDP(network, locAddr)
+	}
+
+	return n.v.listenUDP(network, locAddr)
+}
+
+// Dial connects to the address on the named network.
+func (n *Net) Dial(network, address string) (net.Conn, error) {
+	if n.v == nil {
+		return net.Dial(network, address)
+	}
+
+	return n.v.dial(network, address)
+}
+
+// CreateDialer creates an instance of vnet.Dialer
+func (n *Net) CreateDialer(dialer *net.Dialer) Dialer {
+	if n.v == nil {
+		return &vDialer{
+			dialer: dialer,
+		}
+	}
+
+	return &vDialer{
+		dialer: dialer,
+		v:      n.v,
+	}
+}
+
+// DialUDP acts like Dial for UDP networks.
+func (n *Net) DialUDP(network string, laddr, raddr *net.UDPAddr) (UDPPacketConn, error) {
+	if n.v == nil {
+		return net.DialUDP(network, laddr, raddr)
+	}
+
+	return n.v.dialUDP(network, laddr, raddr)
+}
+
+// ResolveUDPAddr returns an address of UDP end point.
+func (n *Net) ResolveUDPAddr(network, address string) (*net.UDPAddr, error) {
+	if n.v == nil {
+		return net.ResolveUDPAddr(network, address)
+	}
+
+	return n.v.resolveUDPAddr(network, address)
+}
+
+func (n *Net) getInterface(ifName string) (*Interface, error) {
+	if n.v == nil {
+		return nil, errVNetDisabled
+	}
+
+	return n.v.getInterface(ifName)
+}
+
+func (n *Net) setRouter(r *Router) error {
+	if n.v == nil {
+		return errVNetDisabled
+	}
+
+	return n.v.setRouter(r)
+}
+
+func (n *Net) onInboundChunk(c Chunk) {
+	if n.v == nil {
+		return
+	}
+
+	n.v.onInboundChunk(c)
+}
+
+func (n *Net) getStaticIPs() []net.IP {
+	if n.v == nil {
+		return nil
+	}
+
+	return n.v.staticIPs
+}
+
+// IsVirtual tests if the virtual network is enabled.
+func (n *Net) IsVirtual() bool {
+	return n.v != nil
+}
+
+// Dialer is identical to net.Dialer excepts that its methods
+// (Dial, DialContext) are overridden to use virtual network.
+// Use vnet.CreateDialer() to create an instance of this Dialer.
+type Dialer interface {
+	Dial(network, address string) (net.Conn, error)
+}
+
+type vDialer struct {
+	dialer *net.Dialer
+	v      *vNet
+}
+
+func (d *vDialer) Dial(network, address string) (net.Conn, error) {
+	if d.v == nil {
+		return d.dialer.Dial(network, address)
+	}
+
+	return d.v.dial(network, address)
+}

vendor/github.com/pion/transport/vnet/resolver.go

@@ -0,0 +1,89 @@
+package vnet
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+
+	"github.com/pion/logging"
+)
+
+var (
+	errHostnameEmpty       = errors.New("host name must not be empty")
+	errFailedtoParseIPAddr = errors.New("failed to parse IP address")
+)
+
+type resolverConfig struct {
+	LoggerFactory logging.LoggerFactory
+}
+
+type resolver struct {
+	parent *resolver             // read-only
+	hosts  map[string]net.IP     // requires mutex
+	mutex  sync.RWMutex          // thread-safe
+	log    logging.LeveledLogger // read-only
+}
+
+func newResolver(config *resolverConfig) *resolver {
+	r := &resolver{
+		hosts: map[string]net.IP{},
+		log:   config.LoggerFactory.NewLogger("vnet"),
+	}
+
+	if err := r.addHost("localhost", "127.0.0.1"); err != nil {
+		r.log.Warn("failed to add localhost to resolver")
+	}
+	return r
+}
+
+func (r *resolver) setParent(parent *resolver) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	r.parent = parent
+}
+
+func (r *resolver) addHost(name string, ipAddr string) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	if len(name) == 0 {
+		return errHostnameEmpty
+	}
+	ip := net.ParseIP(ipAddr)
+	if ip == nil {
+		return fmt.Errorf("%w \"%s\"", errFailedtoParseIPAddr, ipAddr)
+	}
+	r.hosts[name] = ip
+	return nil
+}
+
+func (r *resolver) lookUp(hostName string) (net.IP, error) {
+	ip := func() net.IP {
+		r.mutex.RLock()
+		defer r.mutex.RUnlock()
+
+		if ip2, ok := r.hosts[hostName]; ok {
+			return ip2
+		}
+		return nil
+	}()
+	if ip != nil {
+		return ip, nil
+	}
+
+	// mutex must be unlocked before calling into parent resolver
+
+	if r.parent != nil {
+		return r.parent.lookUp(hostName)
+	}
+
+	return nil, &net.DNSError{
+		Err:         "host not found",
+		Name:        hostName,
+		Server:      "vnet resolver",
+		IsTimeout:   false,
+		IsTemporary: false,
+	}
+}

vendor/github.com/pion/transport/vnet/router.go

@@ -0,0 +1,620 @@
+package vnet
+
+import (
+	"errors"
+	"fmt"
+	"math/rand"
+	"net"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/pion/logging"
+)
+
+const (
+	defaultRouterQueueSize = 0 // unlimited
+)
+
+var (
+	errInvalidLocalIPinStaticIPs     = errors.New("invalid local IP in StaticIPs")
+	errLocalIPBeyondStaticIPsSubset  = errors.New("mapped in StaticIPs is beyond subnet")
+	errLocalIPNoStaticsIPsAssociated = errors.New("all StaticIPs must have associated local IPs")
+	errRouterAlreadyStarted          = errors.New("router already started")
+	errRouterAlreadyStopped          = errors.New("router already stopped")
+	errStaticIPisBeyondSubnet        = errors.New("static IP is beyond subnet")
+	errAddressSpaceExhausted         = errors.New("address space exhausted")
+	errNoIPAddrEth0                  = errors.New("no IP address is assigned for eth0")
+)
+
+// Generate a unique router name
+var assignRouterName = func() func() string { //nolint:gochecknoglobals
+	var routerIDCtr uint64
+
+	return func() string {
+		n := atomic.AddUint64(&routerIDCtr, 1)
+		return fmt.Sprintf("router%d", n)
+	}
+}()
+
+// RouterConfig ...
+type RouterConfig struct {
+	// Name of router. If not specified, a unique name will be assigned.
+	Name string
+	// CIDR notation, like "192.0.2.0/24"
+	CIDR string
+	// StaticIPs is an array of static IP addresses to be assigned for this router.
+	// If no static IP address is given, the router will automatically assign
+	// an IP address.
+	// This will be ignored if this router is the root.
+	StaticIPs []string
+	// StaticIP is deprecated. Use StaticIPs.
+	StaticIP string
+	// Internal queue size
+	QueueSize int
+	// Effective only when this router has a parent router
+	NATType *NATType
+	// Minimum Delay
+	MinDelay time.Duration
+	// Max Jitter
+	MaxJitter time.Duration
+	// Logger factory
+	LoggerFactory logging.LoggerFactory
+}
+
+// NIC is a nework inerface controller that interfaces Router
+type NIC interface {
+	getInterface(ifName string) (*Interface, error)
+	onInboundChunk(c Chunk)
+	getStaticIPs() []net.IP
+	setRouter(r *Router) error
+}
+
+// ChunkFilter is a handler users can add to filter chunks.
+// If the filter returns false, the packet will be dropped.
+type ChunkFilter func(c Chunk) bool
+
+// Router ...
+type Router struct {
+	name           string                    // read-only
+	interfaces     []*Interface              // read-only
+	ipv4Net        *net.IPNet                // read-only
+	staticIPs      []net.IP                  // read-only
+	staticLocalIPs map[string]net.IP         // read-only,
+	lastID         byte                      // requires mutex [x], used to assign the last digit of IPv4 address
+	queue          *chunkQueue               // read-only
+	parent         *Router                   // read-only
+	children       []*Router                 // read-only
+	natType        *NATType                  // read-only
+	nat            *networkAddressTranslator // read-only
+	nics           map[string]NIC            // read-only
+	stopFunc       func()                    // requires mutex [x]
+	resolver       *resolver                 // read-only
+	chunkFilters   []ChunkFilter             // requires mutex [x]
+	minDelay       time.Duration             // requires mutex [x]
+	maxJitter      time.Duration             // requires mutex [x]
+	mutex          sync.RWMutex              // thread-safe
+	pushCh         chan struct{}             // writer requires mutex
+	loggerFactory  logging.LoggerFactory     // read-only
+	log            logging.LeveledLogger     // read-only
+}
+
+// NewRouter ...
+func NewRouter(config *RouterConfig) (*Router, error) {
+	loggerFactory := config.LoggerFactory
+	log := loggerFactory.NewLogger("vnet")
+
+	_, ipv4Net, err := net.ParseCIDR(config.CIDR)
+	if err != nil {
+		return nil, err
+	}
+
+	queueSize := defaultRouterQueueSize
+	if config.QueueSize > 0 {
+		queueSize = config.QueueSize
+	}
+
+	// set up network interface, lo0
+	lo0 := NewInterface(net.Interface{
+		Index:        1,
+		MTU:          16384,
+		Name:         lo0String,
+		HardwareAddr: nil,
+		Flags:        net.FlagUp | net.FlagLoopback | net.FlagMulticast,
+	})
+	lo0.AddAddr(&net.IPAddr{IP: net.ParseIP("127.0.0.1"), Zone: ""})
+
+	// set up network interface, eth0
+	eth0 := NewInterface(net.Interface{
+		Index:        2,
+		MTU:          1500,
+		Name:         "eth0",
+		HardwareAddr: newMACAddress(),
+		Flags:        net.FlagUp | net.FlagMulticast,
+	})
+
+	// local host name resolver
+	resolver := newResolver(&resolverConfig{
+		LoggerFactory: config.LoggerFactory,
+	})
+
+	name := config.Name
+	if len(name) == 0 {
+		name = assignRouterName()
+	}
+
+	var staticIPs []net.IP
+	staticLocalIPs := map[string]net.IP{}
+	for _, ipStr := range config.StaticIPs {
+		ipPair := strings.Split(ipStr, "/")
+		if ip := net.ParseIP(ipPair[0]); ip != nil {
+			if len(ipPair) > 1 {
+				locIP := net.ParseIP(ipPair[1])
+				if locIP == nil {
+					return nil, errInvalidLocalIPinStaticIPs
+				}
+				if !ipv4Net.Contains(locIP) {
+					return nil, fmt.Errorf("local IP %s %w", locIP.String(), errLocalIPBeyondStaticIPsSubset)
+				}
+				staticLocalIPs[ip.String()] = locIP
+			}
+			staticIPs = append(staticIPs, ip)
+		}
+	}
+	if len(config.StaticIP) > 0 {
+		log.Warn("StaticIP is deprecated. Use StaticIPs instead")
+		if ip := net.ParseIP(config.StaticIP); ip != nil {
+			staticIPs = append(staticIPs, ip)
+		}
+	}
+
+	if nStaticLocal := len(staticLocalIPs); nStaticLocal > 0 {
+		if nStaticLocal != len(staticIPs) {
+			return nil, errLocalIPNoStaticsIPsAssociated
+		}
+	}
+
+	return &Router{
+		name:           name,
+		interfaces:     []*Interface{lo0, eth0},
+		ipv4Net:        ipv4Net,
+		staticIPs:      staticIPs,
+		staticLocalIPs: staticLocalIPs,
+		queue:          newChunkQueue(queueSize, 0),
+		natType:        config.NATType,
+		nics:           map[string]NIC{},
+		resolver:       resolver,
+		minDelay:       config.MinDelay,
+		maxJitter:      config.MaxJitter,
+		pushCh:         make(chan struct{}, 1),
+		loggerFactory:  loggerFactory,
+		log:            log,
+	}, nil
+}
+
+// caller must hold the mutex
+func (r *Router) getInterfaces() ([]*Interface, error) {
+	if len(r.interfaces) == 0 {
+		return nil, fmt.Errorf("%w is available", errNoInterface)
+	}
+
+	return r.interfaces, nil
+}
+
+func (r *Router) getInterface(ifName string) (*Interface, error) {
+	r.mutex.RLock()
+	defer r.mutex.RUnlock()
+
+	ifs, err := r.getInterfaces()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifc := range ifs {
+		if ifc.Name == ifName {
+			return ifc, nil
+		}
+	}
+
+	return nil, fmt.Errorf("interface %s %w", ifName, errNotFound)
+}
+
+// Start ...
+func (r *Router) Start() error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	if r.stopFunc != nil {
+		return errRouterAlreadyStarted
+	}
+
+	cancelCh := make(chan struct{})
+
+	go func() {
+	loop:
+		for {
+			d, err := r.processChunks()
+			if err != nil {
+				r.log.Errorf("[%s] %s", r.name, err.Error())
+				break
+			}
+
+			if d <= 0 {
+				select {
+				case <-r.pushCh:
+				case <-cancelCh:
+					break loop
+				}
+			} else {
+				t := time.NewTimer(d)
+				select {
+				case <-t.C:
+				case <-cancelCh:
+					break loop
+				}
+			}
+		}
+	}()
+
+	r.stopFunc = func() {
+		close(cancelCh)
+	}
+
+	for _, child := range r.children {
+		if err := child.Start(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// Stop ...
+func (r *Router) Stop() error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	if r.stopFunc == nil {
+		return errRouterAlreadyStopped
+	}
+
+	for _, router := range r.children {
+		r.mutex.Unlock()
+		err := router.Stop()
+		r.mutex.Lock()
+
+		if err != nil {
+			return err
+		}
+	}
+
+	r.stopFunc()
+	r.stopFunc = nil
+	return nil
+}
+
+// caller must hold the mutex
+func (r *Router) addNIC(nic NIC) error {
+	ifc, err := nic.getInterface("eth0")
+	if err != nil {
+		return err
+	}
+
+	var ips []net.IP
+
+	if ips = nic.getStaticIPs(); len(ips) == 0 {
+		// assign an IP address
+		ip, err2 := r.assignIPAddress()
+		if err2 != nil {
+			return err2
+		}
+		ips = append(ips, ip)
+	}
+
+	for _, ip := range ips {
+		if !r.ipv4Net.Contains(ip) {
+			return fmt.Errorf("%w: %s", errStaticIPisBeyondSubnet, r.ipv4Net.String())
+		}
+
+		ifc.AddAddr(&net.IPNet{
+			IP:   ip,
+			Mask: r.ipv4Net.Mask,
+		})
+
+		r.nics[ip.String()] = nic
+	}
+
+	if err = nic.setRouter(r); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// AddRouter adds a chile Router.
+func (r *Router) AddRouter(router *Router) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	// Router is a NIC. Add it as a NIC so that packets are routed to this child
+	// router.
+	err := r.addNIC(router)
+	if err != nil {
+		return err
+	}
+
+	if err = router.setRouter(r); err != nil {
+		return err
+	}
+
+	r.children = append(r.children, router)
+	return nil
+}
+
+// AddChildRouter is like AddRouter, but does not add the child routers NIC to
+// the parent. This has to be done manually by calling AddNet, which allows to
+// use a wrapper around the subrouters NIC.
+// AddNet MUST be called before AddChildRouter.
+func (r *Router) AddChildRouter(router *Router) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	if err := router.setRouter(r); err != nil {
+		return err
+	}
+
+	r.children = append(r.children, router)
+	return nil
+}
+
+// AddNet ...
+func (r *Router) AddNet(nic NIC) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	return r.addNIC(nic)
+}
+
+// AddHost adds a mapping of hostname and an IP address to the local resolver.
+func (r *Router) AddHost(hostName string, ipAddr string) error {
+	return r.resolver.addHost(hostName, ipAddr)
+}
+
+// AddChunkFilter adds a filter for chunks traversing this router.
+// You may add more than one filter. The filters are called in the order of this method call.
+// If a chunk is dropped by a filter, subsequent filter will not receive the chunk.
+func (r *Router) AddChunkFilter(filter ChunkFilter) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	r.chunkFilters = append(r.chunkFilters, filter)
+}
+
+// caller should hold the mutex
+func (r *Router) assignIPAddress() (net.IP, error) {
+	// See: https://stackoverflow.com/questions/14915188/ip-address-ending-with-zero
+
+	if r.lastID == 0xfe {
+		return nil, errAddressSpaceExhausted
+	}
+
+	ip := make(net.IP, 4)
+	copy(ip, r.ipv4Net.IP[:3])
+	r.lastID++
+	ip[3] = r.lastID
+	return ip, nil
+}
+
+func (r *Router) push(c Chunk) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	r.log.Debugf("[%s] route %s", r.name, c.String())
+	if r.stopFunc != nil {
+		c.setTimestamp()
+		if r.queue.push(c) {
+			select {
+			case r.pushCh <- struct{}{}:
+			default:
+			}
+		} else {
+			r.log.Warnf("[%s] queue was full. dropped a chunk", r.name)
+		}
+	}
+}
+
+func (r *Router) processChunks() (time.Duration, error) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	// Introduce jitter by delaying the processing of chunks.
+	if r.maxJitter > 0 {
+		jitter := time.Duration(rand.Int63n(int64(r.maxJitter))) //nolint:gosec
+		time.Sleep(jitter)
+	}
+
+	//      cutOff
+	//         v min delay
+	//         |<--->|
+	//  +------------:--
+	//  |OOOOOOXXXXX :   --> time
+	//  +------------:--
+	//  |<--->|     now
+	//    due
+
+	enteredAt := time.Now()
+	cutOff := enteredAt.Add(-r.minDelay)
+
+	var d time.Duration // the next sleep duration
+
+	for {
+		d = 0
+
+		c := r.queue.peek()
+		if c == nil {
+			break // no more chunk in the queue
+		}
+
+		// check timestamp to find if the chunk is due
+		if c.getTimestamp().After(cutOff) {
+			// There is one or more chunk in the queue but none of them are due.
+			// Calculate the next sleep duration here.
+			nextExpire := c.getTimestamp().Add(r.minDelay)
+			d = nextExpire.Sub(enteredAt)
+			break
+		}
+
+		var ok bool
+		if c, ok = r.queue.pop(); !ok {
+			break // no more chunk in the queue
+		}
+
+		blocked := false
+		for i := 0; i < len(r.chunkFilters); i++ {
+			filter := r.chunkFilters[i]
+			if !filter(c) {
+				blocked = true
+				break
+			}
+		}
+		if blocked {
+			continue // discard
+		}
+
+		dstIP := c.getDestinationIP()
+
+		// check if the desination is in our subnet
+		if r.ipv4Net.Contains(dstIP) {
+			// search for the destination NIC
+			var nic NIC
+			if nic, ok = r.nics[dstIP.String()]; !ok {
+				// NIC not found. drop it.
+				r.log.Debugf("[%s] %s unreachable", r.name, c.String())
+				continue
+			}
+
+			// found the NIC, forward the chunk to the NIC.
+			// call to NIC must unlock mutex
+			r.mutex.Unlock()
+			nic.onInboundChunk(c)
+			r.mutex.Lock()
+			continue
+		}
+
+		// the destination is outside of this subnet
+		// is this WAN?
+		if r.parent == nil {
+			// this WAN. No route for this chunk
+			r.log.Debugf("[%s] no route found for %s", r.name, c.String())
+			continue
+		}
+
+		// Pass it to the parent via NAT
+		toParent, err := r.nat.translateOutbound(c)
+		if err != nil {
+			return 0, err
+		}
+
+		if toParent == nil {
+			continue
+		}
+
+		//nolint:godox
+		/* FIXME: this implementation would introduce a duplicate packet!
+		if r.nat.natType.Hairpining {
+			hairpinned, err := r.nat.translateInbound(toParent)
+			if err != nil {
+				r.log.Warnf("[%s] %s", r.name, err.Error())
+			} else {
+				go func() {
+					r.push(hairpinned)
+				}()
+			}
+		}
+		*/
+
+		// call to parent router mutex unlock mutex
+		r.mutex.Unlock()
+		r.parent.push(toParent)
+		r.mutex.Lock()
+	}
+
+	return d, nil
+}
+
+// caller must hold the mutex
+func (r *Router) setRouter(parent *Router) error {
+	r.parent = parent
+	r.resolver.setParent(parent.resolver)
+
+	// when this method is called, one or more IP address has already been assigned by
+	// the parent router.
+	ifc, err := r.getInterface("eth0")
+	if err != nil {
+		return err
+	}
+
+	if len(ifc.addrs) == 0 {
+		return errNoIPAddrEth0
+	}
+
+	mappedIPs := []net.IP{}
+	localIPs := []net.IP{}
+
+	for _, ifcAddr := range ifc.addrs {
+		var ip net.IP
+		switch addr := ifcAddr.(type) {
+		case *net.IPNet:
+			ip = addr.IP
+		case *net.IPAddr: // Do we really need this case?
+			ip = addr.IP
+		default:
+		}
+
+		if ip == nil {
+			continue
+		}
+
+		mappedIPs = append(mappedIPs, ip)
+
+		if locIP := r.staticLocalIPs[ip.String()]; locIP != nil {
+			localIPs = append(localIPs, locIP)
+		}
+	}
+
+	// Set up NAT here
+	if r.natType == nil {
+		r.natType = &NATType{
+			MappingBehavior:   EndpointIndependent,
+			FilteringBehavior: EndpointAddrPortDependent,
+			Hairpining:        false,
+			PortPreservation:  false,
+			MappingLifeTime:   30 * time.Second,
+		}
+	}
+	r.nat, err = newNAT(&natConfig{
+		name:          r.name,
+		natType:       *r.natType,
+		mappedIPs:     mappedIPs,
+		localIPs:      localIPs,
+		loggerFactory: r.loggerFactory,
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *Router) onInboundChunk(c Chunk) {
+	fromParent, err := r.nat.translateInbound(c)
+	if err != nil {
+		r.log.Warnf("[%s] %s", r.name, err.Error())
+		return
+	}
+
+	r.push(fromParent)
+}
+
+func (r *Router) getStaticIPs() []net.IP {
+	return r.staticIPs
+}

vendor/github.com/pion/transport/vnet/tbf.go

@@ -0,0 +1,149 @@
+package vnet
+
+import (
+	"sync"
+	"time"
+)
+
+const (
+	// Bit is a single bit
+	Bit = 1
+	// KBit is a kilobit
+	KBit = 1000 * Bit
+	// MBit is a Megabit
+	MBit = 1000 * KBit
+)
+
+// TokenBucketFilter implements a token bucket rate limit algorithm.
+type TokenBucketFilter struct {
+	NIC
+	currentTokensInBucket int
+	c                     chan Chunk
+	queue                 *chunkQueue
+	queueSize             int // in bytes
+
+	mutex    sync.Mutex
+	rate     int
+	maxBurst int
+
+	wg   sync.WaitGroup
+	done chan struct{}
+}
+
+// TBFOption is the option type to configure a TokenBucketFilter
+type TBFOption func(*TokenBucketFilter) TBFOption
+
+// TBFQueueSizeInBytes sets the max number of bytes waiting in the queue. Can
+// only be set in constructor before using the TBF.
+func TBFQueueSizeInBytes(bytes int) TBFOption {
+	return func(t *TokenBucketFilter) TBFOption {
+		prev := t.queueSize
+		t.queueSize = bytes
+		return TBFQueueSizeInBytes(prev)
+	}
+}
+
+// TBFRate sets the bitrate of a TokenBucketFilter
+func TBFRate(rate int) TBFOption {
+	return func(t *TokenBucketFilter) TBFOption {
+		t.mutex.Lock()
+		defer t.mutex.Unlock()
+		previous := t.rate
+		t.rate = rate
+		return TBFRate(previous)
+	}
+}
+
+// TBFMaxBurst sets the bucket size of the token bucket filter. This is the
+// maximum size that can instantly leave the filter, if the bucket is full.
+func TBFMaxBurst(size int) TBFOption {
+	return func(t *TokenBucketFilter) TBFOption {
+		t.mutex.Lock()
+		defer t.mutex.Unlock()
+		previous := t.maxBurst
+		t.maxBurst = size
+		return TBFMaxBurst(previous)
+	}
+}
+
+// Set updates a setting on the token bucket filter
+func (t *TokenBucketFilter) Set(opts ...TBFOption) (previous TBFOption) {
+	for _, opt := range opts {
+		previous = opt(t)
+	}
+	return previous
+}
+
+// NewTokenBucketFilter creates and starts a new TokenBucketFilter
+func NewTokenBucketFilter(n NIC, opts ...TBFOption) (*TokenBucketFilter, error) {
+	tbf := &TokenBucketFilter{
+		NIC:                   n,
+		currentTokensInBucket: 0,
+		c:                     make(chan Chunk),
+		queue:                 nil,
+		queueSize:             50000,
+		mutex:                 sync.Mutex{},
+		rate:                  1 * MBit,
+		maxBurst:              2 * KBit,
+		wg:                    sync.WaitGroup{},
+		done:                  make(chan struct{}),
+	}
+	tbf.Set(opts...)
+	tbf.queue = newChunkQueue(0, tbf.queueSize)
+	tbf.wg.Add(1)
+	go tbf.run()
+	return tbf, nil
+}
+
+func (t *TokenBucketFilter) onInboundChunk(c Chunk) {
+	t.c <- c
+}
+
+func (t *TokenBucketFilter) run() {
+	defer t.wg.Done()
+	ticker := time.NewTicker(1 * time.Millisecond)
+
+	for {
+		select {
+		case <-t.done:
+			ticker.Stop()
+			t.drainQueue()
+			return
+		case <-ticker.C:
+			t.mutex.Lock()
+			if t.currentTokensInBucket < t.maxBurst {
+				// add (bitrate * S) / 1000 converted to bytes (divide by 8) S
+				// is the update interval in milliseconds
+				t.currentTokensInBucket += (t.rate / 1000) / 8
+			}
+			t.mutex.Unlock()
+			t.drainQueue()
+		case chunk := <-t.c:
+			t.queue.push(chunk)
+			t.drainQueue()
+		}
+	}
+}
+
+func (t *TokenBucketFilter) drainQueue() {
+	for {
+		next := t.queue.peek()
+		if next == nil {
+			break
+		}
+		tokens := len(next.UserData())
+		if t.currentTokensInBucket < tokens {
+			break
+		}
+		t.queue.pop()
+		t.NIC.onInboundChunk(next)
+		t.currentTokensInBucket -= tokens
+	}
+}
+
+// Close closes and stops the token bucket filter queue
+func (t *TokenBucketFilter) Close() error {
+	close(t.done)
+	t.wg.Wait()
+	return nil
+}

vendor/github.com/pion/transport/vnet/udpproxy.go

@@ -0,0 +1,215 @@
+package vnet
+
+import (
+	"context"
+	"net"
+	"sync"
+	"time"
+)
+
+// UDPProxy is a proxy between real server(net.UDPConn) and vnet.UDPConn.
+//
+// High level design:
+//                           ..............................................
+//                           :         Virtual Network (vnet)             :
+//                           :                                            :
+//   +-------+ *         1 +----+         +--------+                      :
+//   | :App  |------------>|:Net|--o<-----|:Router |          .............................
+//   +-------+             +----+         |        |          :        UDPProxy           :
+//                           :            |        |       +----+     +---------+     +---------+     +--------+
+//                           :            |        |--->o--|:Net|-->o-| vnet.   |-->o-|  net.   |--->-| :Real  |
+//                           :            |        |       +----+     | UDPConn |     | UDPConn |     | Server |
+//                           :            |        |          :       +---------+     +---------+     +--------+
+//                           :            |        |          ............................:
+//                           :            +--------+                       :
+//                           ...............................................
+type UDPProxy struct {
+	// The router bind to.
+	router *Router
+
+	// Each vnet source, bind to a real socket to server.
+	// key is real server addr, which is net.Addr
+	// value is *aUDPProxyWorker
+	workers sync.Map
+
+	// For each endpoint, we never know when to start and stop proxy,
+	// so we stop the endpoint when timeout.
+	timeout time.Duration
+
+	// For utest, to mock the target real server.
+	// Optional, use the address of received client packet.
+	mockRealServerAddr *net.UDPAddr
+}
+
+// NewProxy create a proxy, the router for this proxy belongs/bind to. If need to proxy for
+// please create a new proxy for each router. For all addresses we proxy, we will create a
+// vnet.Net in this router and proxy all packets.
+func NewProxy(router *Router) (*UDPProxy, error) {
+	v := &UDPProxy{router: router, timeout: 2 * time.Minute}
+	return v, nil
+}
+
+// Close the proxy, stop all workers.
+func (v *UDPProxy) Close() error {
+	v.workers.Range(func(key, value interface{}) bool {
+		_ = value.(*aUDPProxyWorker).Close()
+		return true
+	})
+	return nil
+}
+
+// Proxy starts a worker for server, ignore if already started.
+func (v *UDPProxy) Proxy(client *Net, server *net.UDPAddr) error {
+	// Note that even if the worker exists, it's also ok to create a same worker,
+	// because the router will use the last one, and the real server will see a address
+	// change event after we switch to the next worker.
+	if _, ok := v.workers.Load(server.String()); ok {
+		// nolint:godox // TODO: Need to restart the stopped worker?
+		return nil
+	}
+
+	// Not exists, create a new one.
+	worker := &aUDPProxyWorker{
+		router: v.router, mockRealServerAddr: v.mockRealServerAddr,
+	}
+
+	// Create context for cleanup.
+	var ctx context.Context
+	ctx, worker.ctxDisposeCancel = context.WithCancel(context.Background())
+
+	v.workers.Store(server.String(), worker)
+
+	return worker.Proxy(ctx, client, server)
+}
+
+// A proxy worker for a specified proxy server.
+type aUDPProxyWorker struct {
+	router             *Router
+	mockRealServerAddr *net.UDPAddr
+
+	// Each vnet source, bind to a real socket to server.
+	// key is vnet client addr, which is net.Addr
+	// value is *net.UDPConn
+	endpoints sync.Map
+
+	// For cleanup.
+	ctxDisposeCancel context.CancelFunc
+	wg               sync.WaitGroup
+}
+
+func (v *aUDPProxyWorker) Close() error {
+	// Notify all goroutines to dispose.
+	v.ctxDisposeCancel()
+
+	// Wait for all goroutines quit.
+	v.wg.Wait()
+
+	return nil
+}
+
+func (v *aUDPProxyWorker) Proxy(ctx context.Context, client *Net, serverAddr *net.UDPAddr) error { // nolint:gocognit
+	// Create vnet for real server by serverAddr.
+	nw := NewNet(&NetConfig{
+		StaticIP: serverAddr.IP.String(),
+	})
+	if err := v.router.AddNet(nw); err != nil {
+		return err
+	}
+
+	// We must create a "same" vnet.UDPConn as the net.UDPConn,
+	// which has the same ip:port, to copy packets between them.
+	vnetSocket, err := nw.ListenUDP("udp4", serverAddr)
+	if err != nil {
+		return err
+	}
+
+	// User stop proxy, we should close the socket.
+	go func() {
+		<-ctx.Done()
+		_ = vnetSocket.Close()
+	}()
+
+	// Got new vnet client, start a new endpoint.
+	findEndpointBy := func(addr net.Addr) (*net.UDPConn, error) {
+		// Exists binding.
+		if value, ok := v.endpoints.Load(addr.String()); ok {
+			// Exists endpoint, reuse it.
+			return value.(*net.UDPConn), nil
+		}
+
+		// The real server we proxy to, for utest to mock it.
+		realAddr := serverAddr
+		if v.mockRealServerAddr != nil {
+			realAddr = v.mockRealServerAddr
+		}
+
+		// Got new vnet client, create new endpoint.
+		realSocket, err := net.DialUDP("udp4", nil, realAddr)
+		if err != nil {
+			return nil, err
+		}
+
+		// User stop proxy, we should close the socket.
+		go func() {
+			<-ctx.Done()
+			_ = realSocket.Close()
+		}()
+
+		// Bind address.
+		v.endpoints.Store(addr.String(), realSocket)
+
+		// Got packet from real serverAddr, we should proxy it to vnet.
+		v.wg.Add(1)
+		go func(vnetClientAddr net.Addr) {
+			defer v.wg.Done()
+
+			buf := make([]byte, 1500)
+			for {
+				n, _, err := realSocket.ReadFrom(buf)
+				if err != nil {
+					return
+				}
+
+				if n <= 0 {
+					continue // Drop packet
+				}
+
+				if _, err := vnetSocket.WriteTo(buf[:n], vnetClientAddr); err != nil {
+					return
+				}
+			}
+		}(addr)
+
+		return realSocket, nil
+	}
+
+	// Start a proxy goroutine.
+	v.wg.Add(1)
+	go func() {
+		defer v.wg.Done()
+
+		buf := make([]byte, 1500)
+
+		for {
+			n, addr, err := vnetSocket.ReadFrom(buf)
+			if err != nil {
+				return
+			}
+
+			if n <= 0 || addr == nil {
+				continue // Drop packet
+			}
+
+			realSocket, err := findEndpointBy(addr)
+			if err != nil {
+				continue // Drop packet.
+			}
+
+			if _, err := realSocket.Write(buf[:n]); err != nil {
+				return
+			}
+		}
+	}()
+
+	return nil
+}

vendor/github.com/pion/transport/vnet/udpproxy_direct.go

@@ -0,0 +1,44 @@
+package vnet
+
+import (
+	"fmt"
+	"net"
+)
+
+// Deliver directly send packet to vnet or real-server.
+// For example, we can use this API to simulate the REPLAY ATTACK.
+func (v *UDPProxy) Deliver(sourceAddr, destAddr net.Addr, b []byte) (nn int, err error) {
+	v.workers.Range(func(key, value interface{}) bool {
+		if nn, err = value.(*aUDPProxyWorker).Deliver(sourceAddr, destAddr, b); err != nil {
+			return false // Fail, abort.
+		} else if nn == len(b) {
+			return false // Done.
+		}
+
+		return true // Deliver by next worker.
+	})
+	return
+}
+
+func (v *aUDPProxyWorker) Deliver(sourceAddr, destAddr net.Addr, b []byte) (nn int, err error) {
+	addr, ok := sourceAddr.(*net.UDPAddr)
+	if !ok {
+		return 0, fmt.Errorf("invalid addr %v", sourceAddr) // nolint:goerr113
+	}
+
+	// nolint:godox // TODO: Support deliver packet from real server to vnet.
+	// If packet is from vnet, proxy to real server.
+	var realSocket *net.UDPConn
+	if value, ok := v.endpoints.Load(addr.String()); !ok {
+		return 0, nil
+	} else { // nolint:golint
+		realSocket = value.(*net.UDPConn)
+	}
+
+	// Send to real server.
+	if _, err := realSocket.Write(b); err != nil {
+		return 0, err
+	}
+
+	return len(b), nil
+}

vendor/github.com/pion/transport/vnet/vnet.go

@@ -0,0 +1,2 @@
+// Package vnet provides a virtual network layer for pion
+package vnet