Allow dual stack sockets to operate on AF_INET

Fixes #1490
Fixes #1495

PiperOrigin-RevId: 289523250

4 files changed, 64 insertions, 65 deletions

diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index a47ceba54..113b457fb 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -547,6 +547,49 @@ type TransportEndpointInfo struct {
 	RegisterNICID tcpip.NICID
 }
 
+// AddrNetProto unwraps the specified address if it is a V4-mapped V6 address
+// and returns the network protocol number to be used to communicate with the
+// specified address. It returns an error if the passed address is incompatible
+// with the receiver.
+func (e *TransportEndpointInfo) AddrNetProto(addr tcpip.FullAddress, v6only bool) (tcpip.FullAddress, tcpip.NetworkProtocolNumber, *tcpip.Error) {
+	netProto := e.NetProto
+	switch len(addr.Addr) {
+	case header.IPv4AddressSize:
+		netProto = header.IPv4ProtocolNumber
+	case header.IPv6AddressSize:
+		if header.IsV4MappedAddress(addr.Addr) {
+			netProto = header.IPv4ProtocolNumber
+			addr.Addr = addr.Addr[header.IPv6AddressSize-header.IPv4AddressSize:]
+			if addr.Addr == header.IPv4Any {
+				addr.Addr = ""
+			}
+		}
+	}
+
+	switch len(e.ID.LocalAddress) {
+	case header.IPv4AddressSize:
+		if len(addr.Addr) == header.IPv6AddressSize {
+			return tcpip.FullAddress{}, 0, tcpip.ErrInvalidEndpointState
+		}
+	case header.IPv6AddressSize:
+		if len(addr.Addr) == header.IPv4AddressSize {
+			return tcpip.FullAddress{}, 0, tcpip.ErrNetworkUnreachable
+		}
+	}
+
+	switch {
+	case netProto == e.NetProto:
+	case netProto == header.IPv4ProtocolNumber && e.NetProto == header.IPv6ProtocolNumber:
+		if v6only {
+			return tcpip.FullAddress{}, 0, tcpip.ErrNoRoute
+		}
+	default:
+		return tcpip.FullAddress{}, 0, tcpip.ErrInvalidEndpointState
+	}
+
+	return addr, netProto, nil
+}
+
 // IsEndpointInfo is an empty method to implement the tcpip.EndpointInfo
 // marker interface.
 func (*TransportEndpointInfo) IsEndpointInfo() {}
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 330786f4c..42afb3f5b 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -288,7 +288,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 
 		toCopy := *to
 		to = &toCopy
-		netProto, err := e.checkV4Mapped(to, true)
+		netProto, err := e.checkV4Mapped(to)
 		if err != nil {
 			return 0, nil, err
 		}
@@ -475,18 +475,12 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Err
 	})
 }
 
-func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress, allowMismatch bool) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
-	netProto := e.NetProto
-	if header.IsV4MappedAddress(addr.Addr) {
-		return 0, tcpip.ErrNoRoute
-	}
-
-	// Fail if we're bound to an address length different from the one we're
-	// checking.
-	if l := len(e.ID.LocalAddress); !allowMismatch && l != 0 && l != len(addr.Addr) {
-		return 0, tcpip.ErrInvalidEndpointState
+func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
+	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProto(*addr, false /* v6only */)
+	if err != nil {
+		return 0, err
 	}
-
+	*addr = unwrapped
 	return netProto, nil
 }
 
@@ -518,7 +512,7 @@ func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	netProto, err := e.checkV4Mapped(&addr, false)
+	netProto, err := e.checkV4Mapped(&addr)
 	if err != nil {
 		return err
 	}
@@ -631,7 +625,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	netProto, err := e.checkV4Mapped(&addr, false)
+	netProto, err := e.checkV4Mapped(&addr)
 	if err != nil {
 		return err
 	}
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index cca511fb9..cc8b533c8 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1691,26 +1691,11 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 }
 
 func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
-	netProto := e.NetProto
-	if header.IsV4MappedAddress(addr.Addr) {
-		// Fail if using a v4 mapped address on a v6only endpoint.
-		if e.v6only {
-			return 0, tcpip.ErrNoRoute
-		}
-
-		netProto = header.IPv4ProtocolNumber
-		addr.Addr = addr.Addr[header.IPv6AddressSize-header.IPv4AddressSize:]
-		if addr.Addr == header.IPv4Any {
-			addr.Addr = ""
-		}
-	}
-
-	// Fail if we're bound to an address length different from the one we're
-	// checking.
-	if l := len(e.ID.LocalAddress); l != 0 && len(addr.Addr) != 0 && l != len(addr.Addr) {
-		return 0, tcpip.ErrInvalidEndpointState
+	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProto(*addr, e.v6only)
+	if err != nil {
+		return 0, err
 	}
-
+	*addr = unwrapped
 	return netProto, nil
 }
 
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index a4ff29a7d..13446f5d9 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -402,7 +402,7 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c
 			return 0, nil, tcpip.ErrBroadcastDisabled
 		}
 
-		netProto, err := e.checkV4Mapped(to, false)
+		netProto, err := e.checkV4Mapped(to)
 		if err != nil {
 			return 0, nil, err
 		}
@@ -501,7 +501,7 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		defer e.mu.Unlock()
 
 		fa := tcpip.FullAddress{Addr: v.InterfaceAddr}
-		netProto, err := e.checkV4Mapped(&fa, false)
+		netProto, err := e.checkV4Mapped(&fa)
 		if err != nil {
 			return err
 		}
@@ -839,35 +839,12 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 	return nil
 }
 
-func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress, allowMismatch bool) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
-	netProto := e.NetProto
-	if len(addr.Addr) == 0 {
-		return netProto, nil
-	}
-	if header.IsV4MappedAddress(addr.Addr) {
-		// Fail if using a v4 mapped address on a v6only endpoint.
-		if e.v6only {
-			return 0, tcpip.ErrNoRoute
-		}
-
-		netProto = header.IPv4ProtocolNumber
-		addr.Addr = addr.Addr[header.IPv6AddressSize-header.IPv4AddressSize:]
-		if addr.Addr == header.IPv4Any {
-			addr.Addr = ""
-		}
-
-		// Fail if we are bound to an IPv6 address.
-		if !allowMismatch && len(e.ID.LocalAddress) == 16 {
-			return 0, tcpip.ErrNetworkUnreachable
-		}
-	}
-
-	// Fail if we're bound to an address length different from the one we're
-	// checking.
-	if l := len(e.ID.LocalAddress); l != 0 && l != len(addr.Addr) {
-		return 0, tcpip.ErrInvalidEndpointState
+func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
+	unwrapped, netProto, err := e.TransportEndpointInfo.AddrNetProto(*addr, e.v6only)
+	if err != nil {
+		return 0, err
 	}
-
+	*addr = unwrapped
 	return netProto, nil
 }
 
@@ -916,7 +893,7 @@ func (e *endpoint) Disconnect() *tcpip.Error {
 
 // Connect connects the endpoint to its peer. Specifying a NIC is optional.
 func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
-	netProto, err := e.checkV4Mapped(&addr, false)
+	netProto, err := e.checkV4Mapped(&addr)
 	if err != nil {
 		return err
 	}
@@ -1074,7 +1051,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	netProto, err := e.checkV4Mapped(&addr, true)
+	netProto, err := e.checkV4Mapped(&addr)
 	if err != nil {
 		return err
 	}