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

1 files changed, 14 insertions, 2 deletions

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)