Handle subnet and broadcast addresses correctly with NIC.subnets

This also renames "subnet" to "addressRange" to avoid any more confusion with
an interface IP's subnet.

Lastly, this also removes the Stack.ContainsSubnet(..) API since it isn't used
by anyone. Plus the same information can be obtained from
Stack.NICAddressRanges().

PiperOrigin-RevId: 267229843

1 files changed, 33 insertions, 30 deletions

diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index ae56e0ffd..43719085e 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -36,13 +36,13 @@ type NIC struct {
 
 	demux *transportDemuxer
 
-	mu          sync.RWMutex
-	spoofing    bool
-	promiscuous bool
-	primary     map[tcpip.NetworkProtocolNumber]*ilist.List
-	endpoints   map[NetworkEndpointID]*referencedNetworkEndpoint
-	subnets     []tcpip.Subnet
-	mcastJoins  map[NetworkEndpointID]int32
+	mu            sync.RWMutex
+	spoofing      bool
+	promiscuous   bool
+	primary       map[tcpip.NetworkProtocolNumber]*ilist.List
+	endpoints     map[NetworkEndpointID]*referencedNetworkEndpoint
+	addressRanges []tcpip.Subnet
+	mcastJoins    map[NetworkEndpointID]int32
 
 	stats NICStats
 }
@@ -224,7 +224,17 @@ func (n *NIC) getRefOrCreateTemp(protocol tcpip.NetworkProtocolNumber, address t
 	// the caller or if the address is found in the NIC's subnets.
 	createTempEP := spoofingOrPromiscuous
 	if !createTempEP {
-		for _, sn := range n.subnets {
+		for _, sn := range n.addressRanges {
+			// Skip the subnet address.
+			if address == sn.ID() {
+				continue
+			}
+			// For now just skip the broadcast address, until we support it.
+			// FIXME(b/137608825): Add support for sending/receiving directed
+			// (subnet) broadcast.
+			if address == sn.Broadcast() {
+				continue
+			}
 			if sn.Contains(address) {
 				createTempEP = true
 				break
@@ -381,45 +391,38 @@ func (n *NIC) Addresses() []tcpip.ProtocolAddress {
 	return addrs
 }
 
-// AddSubnet adds a new subnet to n, so that it starts accepting packets
-// targeted at the given address and network protocol.
-func (n *NIC) AddSubnet(protocol tcpip.NetworkProtocolNumber, subnet tcpip.Subnet) {
+// AddAddressRange adds a range of addresses to n, so that it starts accepting
+// packets targeted at the given addresses and network protocol. The range is
+// given by a subnet address, and all addresses contained in the subnet are
+// used except for the subnet address itself and the subnet's broadcast
+// address.
+func (n *NIC) AddAddressRange(protocol tcpip.NetworkProtocolNumber, subnet tcpip.Subnet) {
 	n.mu.Lock()
-	n.subnets = append(n.subnets, subnet)
+	n.addressRanges = append(n.addressRanges, subnet)
 	n.mu.Unlock()
 }
 
-// RemoveSubnet removes the given subnet from n.
-func (n *NIC) RemoveSubnet(subnet tcpip.Subnet) {
+// RemoveAddressRange removes the given address range from n.
+func (n *NIC) RemoveAddressRange(subnet tcpip.Subnet) {
 	n.mu.Lock()
 
 	// Use the same underlying array.
-	tmp := n.subnets[:0]
-	for _, sub := range n.subnets {
+	tmp := n.addressRanges[:0]
+	for _, sub := range n.addressRanges {
 		if sub != subnet {
 			tmp = append(tmp, sub)
 		}
 	}
-	n.subnets = tmp
+	n.addressRanges = tmp
 
 	n.mu.Unlock()
 }
 
-// ContainsSubnet reports whether this NIC contains the given subnet.
-func (n *NIC) ContainsSubnet(subnet tcpip.Subnet) bool {
-	for _, s := range n.Subnets() {
-		if s == subnet {
-			return true
-		}
-	}
-	return false
-}
-
 // Subnets returns the Subnets associated with this NIC.
-func (n *NIC) Subnets() []tcpip.Subnet {
+func (n *NIC) AddressRanges() []tcpip.Subnet {
 	n.mu.RLock()
 	defer n.mu.RUnlock()
-	sns := make([]tcpip.Subnet, 0, len(n.subnets)+len(n.endpoints))
+	sns := make([]tcpip.Subnet, 0, len(n.addressRanges)+len(n.endpoints))
 	for nid := range n.endpoints {
 		sn, err := tcpip.NewSubnet(nid.LocalAddress, tcpip.AddressMask(strings.Repeat("\xff", len(nid.LocalAddress))))
 		if err != nil {
@@ -429,7 +432,7 @@ func (n *NIC) Subnets() []tcpip.Subnet {
 		}
 		sns = append(sns, sn)
 	}
-	return append(sns, n.subnets...)
+	return append(sns, n.addressRanges...)
 }
 
 func (n *NIC) removeEndpointLocked(r *referencedNetworkEndpoint) {