Validate the checksum for incoming ICMPv6 packets

This change validates the ICMPv6 checksum field before further processing an
ICMPv6 packet.

Tests: Unittests to make sure that only ICMPv6 packets with a valid checksum
are accepted/processed. Existing tests using checker.ICMPv6 now also check the
ICMPv6 checksum field.
PiperOrigin-RevId: 276779148

pkg/tcpip/checker/BUILD

@@ -10,6 +10,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/tcpip",
+        "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/seqnum",
     ],

pkg/tcpip/checker/checker.go

@@ -22,6 +22,7 @@ import (
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 )
@@ -639,6 +640,8 @@ func ICMPv4Code(want byte) TransportChecker {
 
 // ICMPv6 creates a checker that checks that the transport protocol is ICMPv6 and
 // potentially additional ICMPv6 header fields.
+//
+// ICMPv6 will validate the checksum field before calling checkers.
 func ICMPv6(checkers ...TransportChecker) NetworkChecker {
 	return func(t *testing.T, h []header.Network) {
 		t.Helper()
@@ -650,6 +653,10 @@ func ICMPv6(checkers ...TransportChecker) NetworkChecker {
 		}
 
 		icmp := header.ICMPv6(last.Payload())
+		if got, want := icmp.Checksum(), header.ICMPv6Checksum(icmp, last.SourceAddress(), last.DestinationAddress(), buffer.VectorisedView{}); got != want {
+			t.Fatalf("Bad ICMPv6 checksum; got %d, want %d", got, want)
+		}
+
 		for _, f := range checkers {
 			f(t, icmp)
 		}

pkg/tcpip/header/icmpv6.go

@@ -132,7 +132,7 @@ func (b ICMPv6) Checksum() uint16 {
 	return binary.BigEndian.Uint16(b[icmpv6ChecksumOffset:])
 }
 
-// SetChecksum calculates and sets the ICMP checksum field.
+// SetChecksum sets the ICMP checksum field.
 func (b ICMPv6) SetChecksum(checksum uint16) {
 	binary.BigEndian.PutUint16(b[icmpv6ChecksumOffset:], checksum)
 }
@@ -197,7 +197,7 @@ func (b ICMPv6) Payload() []byte {
 	return b[ICMPv6PayloadOffset:]
 }
 
-// ICMPv6Checksum calculates the ICMP checksum over the provided ICMP header,
+// ICMPv6Checksum calculates the ICMP checksum over the provided ICMPv6 header,
 // IPv6 src/dst addresses and the payload.
 func ICMPv6Checksum(h ICMPv6, src, dst tcpip.Address, vv buffer.VectorisedView) uint16 {
 	// Calculate the IPv6 pseudo-header upper-layer checksum.

pkg/tcpip/network/ip_test.go

@@ -519,6 +519,7 @@ func TestIPv6ReceiveControl(t *testing.T) {
 	newUint16 := func(v uint16) *uint16 { return &v }
 
 	const mtu = 0xffff
+	const outerSrcAddr = "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xaa"
 	cases := []struct {
 		name           string
 		expectedCount  int
@@ -570,7 +571,7 @@ func TestIPv6ReceiveControl(t *testing.T) {
 				PayloadLength: uint16(len(view) - header.IPv6MinimumSize - c.trunc),
 				NextHeader:    uint8(header.ICMPv6ProtocolNumber),
 				HopLimit:      20,
-				SrcAddr:       "\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xaa",
+				SrcAddr:       outerSrcAddr,
 				DstAddr:       localIpv6Addr,
 			})
 
@@ -618,6 +619,10 @@ func TestIPv6ReceiveControl(t *testing.T) {
 			o.extra = c.expectedExtra
 
 			vv := view[:len(view)-c.trunc].ToVectorisedView()
+
+			// Set ICMPv6 checksum.
+			icmp.SetChecksum(header.ICMPv6Checksum(icmp, outerSrcAddr, localIpv6Addr, buffer.VectorisedView{}))
+
 			ep.HandlePacket(&r, vv)
 			if want := c.expectedCount; o.controlCalls != want {
 				t.Fatalf("Bad number of control calls for %q case: got %v, want %v", c.name, o.controlCalls, want)

pkg/tcpip/network/ipv6/icmp.go

@@ -72,6 +72,18 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V
 	h := header.ICMPv6(v)
 	iph := header.IPv6(netHeader)
 
+	// Validate ICMPv6 checksum before processing the packet.
+	//
+	// Only the first view in vv is accounted for by h. To account for the
+	// rest of vv, a shallow copy is made and the first view is removed.
+	// This copy is used as extra payload during the checksum calculation.
+	payload := vv
+	payload.RemoveFirst()
+	if got, want := h.Checksum(), header.ICMPv6Checksum(h, iph.SourceAddress(), iph.DestinationAddress(), payload); got != want {
+		received.Invalid.Increment()
+		return
+	}
+
 	// As per RFC 4861 sections 4.1 - 4.5, 6.1.1, 6.1.2, 7.1.1, 7.1.2 and
 	// 8.1, nodes MUST silently drop NDP packets where the Hop Limit field
 	// in the IPv6 header is not set to 255.

pkg/tcpip/transport/icmp/endpoint.go

@@ -445,13 +445,13 @@ func send6(r *stack.Route, ident uint16, data buffer.View, ttl uint8) *tcpip.Err
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	icmpv6.SetChecksum(0)
-	icmpv6.SetChecksum(^header.Checksum(icmpv6, header.Checksum(data, 0)))
+	dataVV := data.ToVectorisedView()
+	icmpv6.SetChecksum(header.ICMPv6Checksum(icmpv6, r.LocalAddress, r.RemoteAddress, dataVV))
 
 	if ttl == 0 {
 		ttl = r.DefaultTTL()
 	}
-	return r.WritePacket(nil /* gso */, hdr, data.ToVectorisedView(), stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS})
+	return r.WritePacket(nil /* gso */, hdr, dataVV, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: ttl, TOS: stack.DefaultTOS})
 }
 
 func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress, allowMismatch bool) (tcpip.NetworkProtocolNumber, *tcpip.Error) {