Support performing DAD for any address

...as long as the network protocol supports duplicate address detection.

This CL provides the facilities for a netstack integrator to perform
DAD.

DHCP recommends that clients effectively perform DAD before accepting an
offer. As per RFC 2131 section 4.4.1 pg 38,

  The client SHOULD perform a check on the suggested address to ensure
  that the address is not already in use.  For example, if the client
  is on a network that supports ARP, the client may issue an ARP request
  for the suggested request.

The implementation of ARP-based IPv4 DAD effectively operates the same
as IPv6's NDP DAD - using ARP requests and responses in place of
NDP neighbour solicitations and advertisements, respectively.

DAD performed by calls to (*Stack).CheckDuplicateAddress don't interfere
with DAD performed when a new IPv6 address is added. This is so that
integrator requests to check for duplicate addresses aren't unexpectedly
aborted when addresses are removed.

A network package internal package provides protocol agnostic DAD state
management that specific protocols that provide DAD can use.

Fixes #4550.

Tests:
  - internal/ip_test.*
  - integration_test.TestDAD
  - arp_test.TestDADARPRequestPacket
  - ipv6.TestCheckDuplicateAddress
PiperOrigin-RevId: 356405593

1 files changed, 92 insertions, 1 deletions

diff --git a/pkg/tcpip/stack/registration.go b/pkg/tcpip/stack/registration.go
index 2bc1c4270..43e9e4beb 100644
--- a/pkg/tcpip/stack/registration.go
+++ b/pkg/tcpip/stack/registration.go
@@ -16,6 +16,7 @@ package stack
 
 import (
 	"fmt"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
@@ -851,7 +852,97 @@ type InjectableLinkEndpoint interface {
 	InjectOutbound(dest tcpip.Address, packet []byte) tcpip.Error
 }
 
-// A LinkAddressResolver handles link address resolution for a network protocol.
+// DADResult is the result of a duplicate address detection process.
+type DADResult struct {
+	// Resolved is true when DAD completed without detecting a duplicate address
+	// on the link.
+	//
+	// Ignored when Err is non-nil.
+	Resolved bool
+
+	// Err is an error encountered while performing DAD.
+	Err tcpip.Error
+}
+
+// DADCompletionHandler is a handler for DAD completion.
+type DADCompletionHandler func(DADResult)
+
+// DADCheckAddressDisposition enumerates the possible return values from
+// DAD.CheckDuplicateAddress.
+type DADCheckAddressDisposition int
+
+const (
+	_ DADCheckAddressDisposition = iota
+
+	// DADDisabled indicates that DAD is disabled.
+	DADDisabled
+
+	// DADStarting indicates that DAD is starting for an address.
+	DADStarting
+
+	// DADAlreadyRunning indicates that DAD was already started for an address.
+	DADAlreadyRunning
+)
+
+const (
+	// defaultDupAddrDetectTransmits is the default number of NDP Neighbor
+	// Solicitation messages to send when doing Duplicate Address Detection
+	// for a tentative address.
+	//
+	// Default = 1 (from RFC 4862 section 5.1)
+	defaultDupAddrDetectTransmits = 1
+)
+
+// DADConfigurations holds configurations for duplicate address detection.
+type DADConfigurations struct {
+	// The number of Neighbor Solicitation messages to send when doing
+	// Duplicate Address Detection for a tentative address.
+	//
+	// Note, a value of zero effectively disables DAD.
+	DupAddrDetectTransmits uint8
+
+	// The amount of time to wait between sending Neighbor Solicitation
+	// messages.
+	//
+	// Must be greater than or equal to 1ms.
+	RetransmitTimer time.Duration
+}
+
+// DefaultDADConfigurations returns the default DAD configurations.
+func DefaultDADConfigurations() DADConfigurations {
+	return DADConfigurations{
+		DupAddrDetectTransmits: defaultDupAddrDetectTransmits,
+		RetransmitTimer:        defaultRetransmitTimer,
+	}
+}
+
+// Validate modifies the configuration with valid values. If invalid values are
+// present in the configurations, the corresponding default values are used
+// instead.
+func (c *DADConfigurations) Validate() {
+	if c.RetransmitTimer < minimumRetransmitTimer {
+		c.RetransmitTimer = defaultRetransmitTimer
+	}
+}
+
+// DuplicateAddressDetector handles checking if an address is already assigned
+// to some neighboring node on the link.
+type DuplicateAddressDetector interface {
+	// CheckDuplicateAddress checks if an address is assigned to a neighbor.
+	//
+	// If DAD is already being performed for the address, the handler will be
+	// called with the result of the original DAD request.
+	CheckDuplicateAddress(tcpip.Address, DADCompletionHandler) DADCheckAddressDisposition
+
+	// SetDADConfiguations sets the configurations for DAD.
+	SetDADConfigurations(c DADConfigurations)
+
+	// DuplicateAddressProtocol returns the network protocol the receiver can
+	// perform duplicate address detection for.
+	DuplicateAddressProtocol() tcpip.NetworkProtocolNumber
+}
+
+// LinkAddressResolver handles link address resolution for a network protocol.
 type LinkAddressResolver interface {
 	// LinkAddressRequest sends a request for the link address of the target
 	// address. The request is broadcasted on the local network if a remote link