Add support for a subnet prefix length on interface network addresses

This allows the user code to add a network address with a subnet prefix length.
The prefix length value is stored in the network endpoint and provided back to
the user in the ProtocolAddress type.

PiperOrigin-RevId: 259807693

5 files changed, 59 insertions, 26 deletions

diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go
index cb35635fc..60070874d 100644
--- a/pkg/tcpip/network/arp/arp.go
+++ b/pkg/tcpip/network/arp/arp.go
@@ -46,7 +46,6 @@ const (
 // endpoint implements stack.NetworkEndpoint.
 type endpoint struct {
 	nicid         tcpip.NICID
-	addr          tcpip.Address
 	linkEP        stack.LinkEndpoint
 	linkAddrCache stack.LinkAddressCache
 }
@@ -73,6 +72,10 @@ func (e *endpoint) ID() *stack.NetworkEndpointID {
 	return &stack.NetworkEndpointID{ProtocolAddress}
 }
 
+func (e *endpoint) PrefixLen() int {
+	return 0
+}
+
 func (e *endpoint) MaxHeaderLength() uint16 {
 	return e.linkEP.MaxHeaderLength() + header.ARPSize
 }
@@ -122,19 +125,19 @@ type protocol struct {
 
 func (p *protocol) Number() tcpip.NetworkProtocolNumber { return ProtocolNumber }
 func (p *protocol) MinimumPacketSize() int              { return header.ARPSize }
+func (p *protocol) DefaultPrefixLen() int               { return 0 }
 
 func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 	h := header.ARP(v)
 	return tcpip.Address(h.ProtocolAddressSender()), ProtocolAddress
 }
 
-func (p *protocol) NewEndpoint(nicid tcpip.NICID, addr tcpip.Address, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, sender stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
-	if addr != ProtocolAddress {
+func (p *protocol) NewEndpoint(nicid tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, sender stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
+	if addrWithPrefix.Address != ProtocolAddress {
 		return nil, tcpip.ErrBadLocalAddress
 	}
 	return &endpoint{
 		nicid:         nicid,
-		addr:          addr,
 		linkEP:        sender,
 		linkAddrCache: linkAddrCache,
 	}, nil
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index 8ff428445..55e9eec99 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -29,16 +29,18 @@ import (
 )
 
 const (
-	localIpv4Addr  = "\x0a\x00\x00\x01"
-	remoteIpv4Addr = "\x0a\x00\x00\x02"
-	ipv4SubnetAddr = "\x0a\x00\x00\x00"
-	ipv4SubnetMask = "\xff\xff\xff\x00"
-	ipv4Gateway    = "\x0a\x00\x00\x03"
-	localIpv6Addr  = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"
-	remoteIpv6Addr = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
-	ipv6SubnetAddr = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
-	ipv6SubnetMask = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00"
-	ipv6Gateway    = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03"
+	localIpv4Addr      = "\x0a\x00\x00\x01"
+	localIpv4PrefixLen = 24
+	remoteIpv4Addr     = "\x0a\x00\x00\x02"
+	ipv4SubnetAddr     = "\x0a\x00\x00\x00"
+	ipv4SubnetMask     = "\xff\xff\xff\x00"
+	ipv4Gateway        = "\x0a\x00\x00\x03"
+	localIpv6Addr      = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"
+	localIpv6PrefixLen = 120
+	remoteIpv6Addr     = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
+	ipv6SubnetAddr     = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+	ipv6SubnetMask     = "\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00"
+	ipv6Gateway        = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03"
 )
 
 // testObject implements two interfaces: LinkEndpoint and TransportDispatcher.
@@ -197,7 +199,7 @@ func buildIPv6Route(local, remote tcpip.Address) (stack.Route, *tcpip.Error) {
 func TestIPv4Send(t *testing.T) {
 	o := testObject{t: t, v4: true}
 	proto := ipv4.NewProtocol()
-	ep, err := proto.NewEndpoint(1, localIpv4Addr, nil, nil, &o)
+	ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv4Addr, localIpv4PrefixLen}, nil, nil, &o)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
 	}
@@ -229,7 +231,7 @@ func TestIPv4Send(t *testing.T) {
 func TestIPv4Receive(t *testing.T) {
 	o := testObject{t: t, v4: true}
 	proto := ipv4.NewProtocol()
-	ep, err := proto.NewEndpoint(1, localIpv4Addr, nil, &o, nil)
+	ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv4Addr, localIpv4PrefixLen}, nil, &o, nil)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
 	}
@@ -295,7 +297,7 @@ func TestIPv4ReceiveControl(t *testing.T) {
 		t.Run(c.name, func(t *testing.T) {
 			o := testObject{t: t}
 			proto := ipv4.NewProtocol()
-			ep, err := proto.NewEndpoint(1, localIpv4Addr, nil, &o, nil)
+			ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv4Addr, localIpv4PrefixLen}, nil, &o, nil)
 			if err != nil {
 				t.Fatalf("NewEndpoint failed: %v", err)
 			}
@@ -359,7 +361,7 @@ func TestIPv4ReceiveControl(t *testing.T) {
 func TestIPv4FragmentationReceive(t *testing.T) {
 	o := testObject{t: t, v4: true}
 	proto := ipv4.NewProtocol()
-	ep, err := proto.NewEndpoint(1, localIpv4Addr, nil, &o, nil)
+	ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv4Addr, localIpv4PrefixLen}, nil, &o, nil)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
 	}
@@ -426,7 +428,7 @@ func TestIPv4FragmentationReceive(t *testing.T) {
 func TestIPv6Send(t *testing.T) {
 	o := testObject{t: t}
 	proto := ipv6.NewProtocol()
-	ep, err := proto.NewEndpoint(1, localIpv6Addr, nil, nil, &o)
+	ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv6Addr, localIpv6PrefixLen}, nil, nil, &o)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
 	}
@@ -458,7 +460,7 @@ func TestIPv6Send(t *testing.T) {
 func TestIPv6Receive(t *testing.T) {
 	o := testObject{t: t}
 	proto := ipv6.NewProtocol()
-	ep, err := proto.NewEndpoint(1, localIpv6Addr, nil, &o, nil)
+	ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv6Addr, localIpv6PrefixLen}, nil, &o, nil)
 	if err != nil {
 		t.Fatalf("NewEndpoint failed: %v", err)
 	}
@@ -532,7 +534,7 @@ func TestIPv6ReceiveControl(t *testing.T) {
 		t.Run(c.name, func(t *testing.T) {
 			o := testObject{t: t}
 			proto := ipv6.NewProtocol()
-			ep, err := proto.NewEndpoint(1, localIpv6Addr, nil, &o, nil)
+			ep, err := proto.NewEndpoint(1, tcpip.AddressWithPrefix{localIpv6Addr, localIpv6PrefixLen}, nil, &o, nil)
 			if err != nil {
 				t.Fatalf("NewEndpoint failed: %v", err)
 			}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index e44a73d96..b7a06f525 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -49,16 +49,18 @@ const (
 type endpoint struct {
 	nicid         tcpip.NICID
 	id            stack.NetworkEndpointID
+	prefixLen     int
 	linkEP        stack.LinkEndpoint
 	dispatcher    stack.TransportDispatcher
 	fragmentation *fragmentation.Fragmentation
 }
 
 // NewEndpoint creates a new ipv4 endpoint.
-func (p *protocol) NewEndpoint(nicid tcpip.NICID, addr tcpip.Address, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
+func (p *protocol) NewEndpoint(nicid tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
 	e := &endpoint{
 		nicid:         nicid,
-		id:            stack.NetworkEndpointID{LocalAddress: addr},
+		id:            stack.NetworkEndpointID{LocalAddress: addrWithPrefix.Address},
+		prefixLen:     addrWithPrefix.PrefixLen,
 		linkEP:        linkEP,
 		dispatcher:    dispatcher,
 		fragmentation: fragmentation.NewFragmentation(fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout),
@@ -93,6 +95,11 @@ func (e *endpoint) ID() *stack.NetworkEndpointID {
 	return &e.id
 }
 
+// PrefixLen returns the ipv4 endpoint subnet prefix length in bits.
+func (e *endpoint) PrefixLen() int {
+	return e.prefixLen
+}
+
 // MaxHeaderLength returns the maximum length needed by ipv4 headers (and
 // underlying protocols).
 func (e *endpoint) MaxHeaderLength() uint16 {
@@ -338,6 +345,11 @@ func (p *protocol) MinimumPacketSize() int {
 	return header.IPv4MinimumSize
 }
 
+// DefaultPrefixLen returns the IPv4 default prefix length.
+func (p *protocol) DefaultPrefixLen() int {
+	return header.IPv4AddressSize * 8
+}
+
 // ParseAddresses implements NetworkProtocol.ParseAddresses.
 func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 	h := header.IPv4(v)
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index d46d68e73..726362c87 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -99,7 +99,11 @@ func TestICMPCounts(t *testing.T) {
 		}},
 	)
 
-	ep, err := s.NetworkProtocolInstance(ProtocolNumber).NewEndpoint(0, lladdr1, &stubLinkAddressCache{}, &stubDispatcher{}, nil)
+	netProto := s.NetworkProtocolInstance(ProtocolNumber)
+	if netProto == nil {
+		t.Fatalf("cannot find protocol instance for network protocol %d", ProtocolNumber)
+	}
+	ep, err := netProto.NewEndpoint(0, tcpip.AddressWithPrefix{lladdr1, netProto.DefaultPrefixLen()}, &stubLinkAddressCache{}, &stubDispatcher{}, nil)
 	if err != nil {
 		t.Fatalf("NewEndpoint(_) = _, %s, want = _, nil", err)
 	}
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index e3e8739fd..331a8bdaa 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -46,6 +46,7 @@ const (
 type endpoint struct {
 	nicid         tcpip.NICID
 	id            stack.NetworkEndpointID
+	prefixLen     int
 	linkEP        stack.LinkEndpoint
 	linkAddrCache stack.LinkAddressCache
 	dispatcher    stack.TransportDispatcher
@@ -72,6 +73,11 @@ func (e *endpoint) ID() *stack.NetworkEndpointID {
 	return &e.id
 }
 
+// PrefixLen returns the ipv6 endpoint subnet prefix length in bits.
+func (e *endpoint) PrefixLen() int {
+	return e.prefixLen
+}
+
 // Capabilities implements stack.NetworkEndpoint.Capabilities.
 func (e *endpoint) Capabilities() stack.LinkEndpointCapabilities {
 	return e.linkEP.Capabilities()
@@ -172,6 +178,11 @@ func (p *protocol) MinimumPacketSize() int {
 	return header.IPv6MinimumSize
 }
 
+// DefaultPrefixLen returns the IPv6 default prefix length.
+func (p *protocol) DefaultPrefixLen() int {
+	return header.IPv6AddressSize * 8
+}
+
 // ParseAddresses implements NetworkProtocol.ParseAddresses.
 func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 	h := header.IPv6(v)
@@ -179,10 +190,11 @@ func (*protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
 }
 
 // NewEndpoint creates a new ipv6 endpoint.
-func (p *protocol) NewEndpoint(nicid tcpip.NICID, addr tcpip.Address, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
+func (p *protocol) NewEndpoint(nicid tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint) (stack.NetworkEndpoint, *tcpip.Error) {
 	return &endpoint{
 		nicid:         nicid,
-		id:            stack.NetworkEndpointID{LocalAddress: addr},
+		id:            stack.NetworkEndpointID{LocalAddress: addrWithPrefix.Address},
+		prefixLen:     addrWithPrefix.PrefixLen,
 		linkEP:        linkEP,
 		linkAddrCache: linkAddrCache,
 		dispatcher:    dispatcher,