1 files changed, 274 insertions, 0 deletions
diff --git a/pkg/dhcp/client.go b/pkg/dhcp/client.go
new file mode 100644
index 000000000..9a4fd7ae4
--- /dev/null
+++ b/pkg/dhcp/client.go
@@ -0,0 +1,274 @@
+// Copyright 2016 The Netstack Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package dhcp
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"fmt"
+	"log"
+	"sync"
+	"time"
+
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/transport/udp"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// Client is a DHCP client.
+type Client struct {
+	stack    *stack.Stack
+	nicid    tcpip.NICID
+	linkAddr tcpip.LinkAddress
+
+	mu          sync.Mutex
+	addr        tcpip.Address
+	cfg         Config
+	lease       time.Duration
+	cancelRenew func()
+}
+
+// NewClient creates a DHCP client.
+//
+// TODO: add s.LinkAddr(nicid) to *stack.Stack.
+func NewClient(s *stack.Stack, nicid tcpip.NICID, linkAddr tcpip.LinkAddress) *Client {
+	return &Client{
+		stack:    s,
+		nicid:    nicid,
+		linkAddr: linkAddr,
+	}
+}
+
+// Start starts the DHCP client.
+// It will periodically search for an IP address using the Request method.
+func (c *Client) Start() {
+	go func() {
+		for {
+			log.Print("DHCP request")
+			ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+			err := c.Request(ctx, "")
+			cancel()
+			if err == nil {
+				break
+			}
+		}
+		log.Printf("DHCP acquired IP %s for %s", c.Address(), c.Config().LeaseLength)
+	}()
+}
+
+// Address reports the IP address acquired by the DHCP client.
+func (c *Client) Address() tcpip.Address {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.addr
+}
+
+// Config reports the DHCP configuration acquired with the IP address lease.
+func (c *Client) Config() Config {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.cfg
+}
+
+// Shutdown relinquishes any lease and ends any outstanding renewal timers.
+func (c *Client) Shutdown() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.addr != "" {
+		c.stack.RemoveAddress(c.nicid, c.addr)
+	}
+	if c.cancelRenew != nil {
+		c.cancelRenew()
+	}
+}
+
+// Request executes a DHCP request session.
+//
+// On success, it adds a new address to this client's TCPIP stack.
+// If the server sets a lease limit a timer is set to automatically
+// renew it.
+func (c *Client) Request(ctx context.Context, requestedAddr tcpip.Address) error {
+	var wq waiter.Queue
+	ep, err := c.stack.NewEndpoint(udp.ProtocolNumber, ipv4.ProtocolNumber, &wq)
+	if err != nil {
+		return fmt.Errorf("dhcp: outbound endpoint: %v", err)
+	}
+	err = ep.Bind(tcpip.FullAddress{
+		Addr: "\x00\x00\x00\x00",
+		Port: clientPort,
+	}, nil)
+	defer ep.Close()
+	if err != nil {
+		return fmt.Errorf("dhcp: connect failed: %v", err)
+	}
+
+	epin, err := c.stack.NewEndpoint(udp.ProtocolNumber, ipv4.ProtocolNumber, &wq)
+	if err != nil {
+		return fmt.Errorf("dhcp: inbound endpoint: %v", err)
+	}
+	err = epin.Bind(tcpip.FullAddress{
+		Addr: "\xff\xff\xff\xff",
+		Port: clientPort,
+	}, nil)
+	defer epin.Close()
+	if err != nil {
+		return fmt.Errorf("dhcp: connect failed: %v", err)
+	}
+
+	var xid [4]byte
+	rand.Read(xid[:])
+
+	// DHCPDISCOVERY
+	options := options{
+		{optDHCPMsgType, []byte{byte(dhcpDISCOVER)}},
+		{optParamReq, []byte{
+			1,  // request subnet mask
+			3,  // request router
+			15, // domain name
+			6,  // domain name server
+		}},
+	}
+	if requestedAddr != "" {
+		options = append(options, option{optReqIPAddr, []byte(requestedAddr)})
+	}
+	h := make(header, headerBaseSize+options.len())
+	h.init()
+	h.setOp(opRequest)
+	copy(h.xidbytes(), xid[:])
+	h.setBroadcast()
+	copy(h.chaddr(), c.linkAddr)
+	h.setOptions(options)
+
+	serverAddr := &tcpip.FullAddress{
+		Addr: "\xff\xff\xff\xff",
+		Port: serverPort,
+	}
+	wopts := tcpip.WriteOptions{
+		To: serverAddr,
+	}
+	if _, err := ep.Write(tcpip.SlicePayload(h), wopts); err != nil {
+		return fmt.Errorf("dhcp discovery write: %v", err)
+	}
+
+	we, ch := waiter.NewChannelEntry(nil)
+	wq.EventRegister(&we, waiter.EventIn)
+	defer wq.EventUnregister(&we)
+
+	// DHCPOFFER
+	for {
+		var addr tcpip.FullAddress
+		v, err := epin.Read(&addr)
+		if err == tcpip.ErrWouldBlock {
+			select {
+			case <-ch:
+				continue
+			case <-ctx.Done():
+				return fmt.Errorf("reading dhcp offer: %v", tcpip.ErrAborted)
+			}
+		}
+		h = header(v)
+		if h.isValid() && h.op() == opReply && bytes.Equal(h.xidbytes(), xid[:]) {
+			break
+		}
+	}
+	if _, err := h.options(); err != nil {
+		return fmt.Errorf("dhcp offer: %v", err)
+	}
+
+	var ack bool
+	var cfg Config
+
+	// DHCPREQUEST
+	addr := tcpip.Address(h.yiaddr())
+	if err := c.stack.AddAddress(c.nicid, ipv4.ProtocolNumber, addr); err != nil {
+		if err != tcpip.ErrDuplicateAddress {
+			return fmt.Errorf("adding address: %v", err)
+		}
+	}
+	defer func() {
+		if ack {
+			c.mu.Lock()
+			c.addr = addr
+			c.cfg = cfg
+			c.mu.Unlock()
+		} else {
+			c.stack.RemoveAddress(c.nicid, addr)
+		}
+	}()
+	h.setOp(opRequest)
+	for i, b := 0, h.yiaddr(); i < len(b); i++ {
+		b[i] = 0
+	}
+	h.setOptions([]option{
+		{optDHCPMsgType, []byte{byte(dhcpREQUEST)}},
+		{optReqIPAddr, []byte(addr)},
+		{optDHCPServer, h.siaddr()},
+	})
+	if _, err := ep.Write(tcpip.SlicePayload(h), wopts); err != nil {
+		return fmt.Errorf("dhcp discovery write: %v", err)
+	}
+
+	// DHCPACK
+	for {
+		var addr tcpip.FullAddress
+		v, err := epin.Read(&addr)
+		if err == tcpip.ErrWouldBlock {
+			select {
+			case <-ch:
+				continue
+			case <-ctx.Done():
+				return fmt.Errorf("reading dhcp ack: %v", tcpip.ErrAborted)
+			}
+		}
+		h = header(v)
+		if h.isValid() && h.op() == opReply && bytes.Equal(h.xidbytes(), xid[:]) {
+			break
+		}
+	}
+	opts, e := h.options()
+	if e != nil {
+		return fmt.Errorf("dhcp ack: %v", e)
+	}
+	if err := cfg.decode(opts); err != nil {
+		return fmt.Errorf("dhcp ack bad options: %v", err)
+	}
+	msgtype, e := opts.dhcpMsgType()
+	if e != nil {
+		return fmt.Errorf("dhcp ack: %v", e)
+	}
+	ack = msgtype == dhcpACK
+	if !ack {
+		return fmt.Errorf("dhcp: request not acknowledged")
+	}
+	if cfg.LeaseLength != 0 {
+		go c.renewAfter(cfg.LeaseLength)
+	}
+	return nil
+}
+
+func (c *Client) renewAfter(d time.Duration) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.cancelRenew != nil {
+		c.cancelRenew()
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	c.cancelRenew = cancel
+	go func() {
+		timer := time.NewTimer(d)
+		defer timer.Stop()
+		select {
+		case <-ctx.Done():
+		case <-timer.C:
+			if err := c.Request(ctx, c.addr); err != nil {
+				log.Printf("address renewal failed: %v", err)
+				go c.renewAfter(1 * time.Minute)
+			}
+		}
+	}()
+}