diff --git a/ipv6/example_test.go b/ipv6/example_test.go
index d0c9695..2f7540f 100644
--- a/ipv6/example_test.go
+++ b/ipv6/example_test.go
@@ -122,8 +122,8 @@
 	}
 	var f ipv6.ICMPFilter
 	f.SetAll(true)
-	f.Set(ipv6.ICMPTypeTimeExceeded, false)
-	f.Set(ipv6.ICMPTypeEchoReply, false)
+	f.Accept(ipv6.ICMPTypeTimeExceeded)
+	f.Accept(ipv6.ICMPTypeEchoReply)
 	if err := p.SetICMPFilter(&f); err != nil {
 		log.Fatal(err)
 	}
diff --git a/ipv6/icmp.go b/ipv6/icmp.go
index 9a6dc2d..a2de65a 100644
--- a/ipv6/icmp.go
+++ b/ipv6/icmp.go
@@ -4,11 +4,7 @@
 
 package ipv6
 
-import (
-	"sync"
-
-	"golang.org/x/net/internal/iana"
-)
+import "golang.org/x/net/internal/iana"
 
 // An ICMPType represents a type of ICMP message.
 type ICMPType int
@@ -27,30 +23,35 @@
 }
 
 // An ICMPFilter represents an ICMP message filter for incoming
-// packets.
+// packets. The filter belongs to a packet delivery path on a host and
+// it cannot interact with forwarding packets or tunnel-outer packets.
+//
+// Note: RFC 2460 defines a reasonable role model. A node means a
+// device that implements IP. A router means a node that forwards IP
+// packets not explicitly addressed to itself, and a host means a node
+// that is not a router.
 type ICMPFilter struct {
-	mu sync.RWMutex
 	sysICMPv6Filter
 }
 
-// Set sets the ICMP type and filter action to the filter.
-func (f *ICMPFilter) Set(typ ICMPType, block bool) {
-	f.mu.Lock()
-	f.set(typ, block)
-	f.mu.Unlock()
+// Accept accepts incoming ICMP packets including the type field value
+// typ.
+func (f *ICMPFilter) Accept(typ ICMPType) {
+	f.accept(typ)
+}
+
+// Block blocks incoming ICMP packets including the type field value
+// typ.
+func (f *ICMPFilter) Block(typ ICMPType) {
+	f.block(typ)
 }
 
 // SetAll sets the filter action to the filter.
 func (f *ICMPFilter) SetAll(block bool) {
-	f.mu.Lock()
 	f.setAll(block)
-	f.mu.Unlock()
 }
 
 // WillBlock reports whether the ICMP type will be blocked.
 func (f *ICMPFilter) WillBlock(typ ICMPType) bool {
-	f.mu.RLock()
-	ok := f.willBlock(typ)
-	f.mu.RUnlock()
-	return ok
+	return f.willBlock(typ)
 }
diff --git a/ipv6/icmp_bsd.go b/ipv6/icmp_bsd.go
index f6f7d78..30e3ce4 100644
--- a/ipv6/icmp_bsd.go
+++ b/ipv6/icmp_bsd.go
@@ -6,12 +6,12 @@
 
 package ipv6
 
-func (f *sysICMPv6Filter) set(typ ICMPType, block bool) {
-	if block {
-		f.Filt[typ>>5] &^= 1 << (uint32(typ) & 31)
-	} else {
-		f.Filt[typ>>5] |= 1 << (uint32(typ) & 31)
-	}
+func (f *sysICMPv6Filter) accept(typ ICMPType) {
+	f.Filt[typ>>5] |= 1 << (uint32(typ) & 31)
+}
+
+func (f *sysICMPv6Filter) block(typ ICMPType) {
+	f.Filt[typ>>5] &^= 1 << (uint32(typ) & 31)
 }
 
 func (f *sysICMPv6Filter) setAll(block bool) {
diff --git a/ipv6/icmp_linux.go b/ipv6/icmp_linux.go
index c04e585..a67ecf6 100644
--- a/ipv6/icmp_linux.go
+++ b/ipv6/icmp_linux.go
@@ -4,12 +4,12 @@
 
 package ipv6
 
-func (f *sysICMPv6Filter) set(typ ICMPType, block bool) {
-	if block {
-		f.Data[typ>>5] |= 1 << (uint32(typ) & 31)
-	} else {
-		f.Data[typ>>5] &^= 1 << (uint32(typ) & 31)
-	}
+func (f *sysICMPv6Filter) accept(typ ICMPType) {
+	f.Data[typ>>5] &^= 1 << (uint32(typ) & 31)
+}
+
+func (f *sysICMPv6Filter) block(typ ICMPType) {
+	f.Data[typ>>5] |= 1 << (uint32(typ) & 31)
 }
 
 func (f *sysICMPv6Filter) setAll(block bool) {
diff --git a/ipv6/icmp_solaris.go b/ipv6/icmp_solaris.go
index b5efef0..a942f35 100644
--- a/ipv6/icmp_solaris.go
+++ b/ipv6/icmp_solaris.go
@@ -6,7 +6,11 @@
 
 package ipv6
 
-func (f *sysICMPv6Filter) set(typ ICMPType, block bool) {
+func (f *sysICMPv6Filter) accept(typ ICMPType) {
+	// TODO(mikio): implement this
+}
+
+func (f *sysICMPv6Filter) block(typ ICMPType) {
 	// TODO(mikio): implement this
 }
 
diff --git a/ipv6/icmp_stub.go b/ipv6/icmp_stub.go
index 58b6a04..c1263ec 100644
--- a/ipv6/icmp_stub.go
+++ b/ipv6/icmp_stub.go
@@ -9,7 +9,10 @@
 type sysICMPv6Filter struct {
 }
 
-func (f *sysICMPv6Filter) set(typ ICMPType, block bool) {
+func (f *sysICMPv6Filter) accept(typ ICMPType) {
+}
+
+func (f *sysICMPv6Filter) block(typ ICMPType) {
 }
 
 func (f *sysICMPv6Filter) setAll(block bool) {
diff --git a/ipv6/icmp_test.go b/ipv6/icmp_test.go
index 6ca2c16..76e02dc 100644
--- a/ipv6/icmp_test.go
+++ b/ipv6/icmp_test.go
@@ -9,7 +9,6 @@
 	"os"
 	"reflect"
 	"runtime"
-	"sync"
 	"testing"
 
 	"golang.org/x/net/ipv6"
@@ -42,27 +41,21 @@
 	var f ipv6.ICMPFilter
 	for _, toggle := range []bool{false, true} {
 		f.SetAll(toggle)
-		var wg sync.WaitGroup
 		for _, typ := range []ipv6.ICMPType{
 			ipv6.ICMPTypeDestinationUnreachable,
 			ipv6.ICMPTypeEchoReply,
 			ipv6.ICMPTypeNeighborSolicitation,
 			ipv6.ICMPTypeDuplicateAddressConfirmation,
 		} {
-			wg.Add(1)
-			go func(typ ipv6.ICMPType) {
-				defer wg.Done()
-				f.Set(typ, false)
-				if f.WillBlock(typ) {
-					t.Errorf("ipv6.ICMPFilter.Set(%v, false) failed", typ)
-				}
-				f.Set(typ, true)
-				if !f.WillBlock(typ) {
-					t.Errorf("ipv6.ICMPFilter.Set(%v, true) failed", typ)
-				}
-			}(typ)
+			f.Accept(typ)
+			if f.WillBlock(typ) {
+				t.Errorf("ipv6.ICMPFilter.Set(%v, false) failed", typ)
+			}
+			f.Block(typ)
+			if !f.WillBlock(typ) {
+				t.Errorf("ipv6.ICMPFilter.Set(%v, true) failed", typ)
+			}
 		}
-		wg.Wait()
 	}
 }
 
@@ -88,8 +81,8 @@
 
 	var f ipv6.ICMPFilter
 	f.SetAll(true)
-	f.Set(ipv6.ICMPTypeEchoRequest, false)
-	f.Set(ipv6.ICMPTypeEchoReply, false)
+	f.Accept(ipv6.ICMPTypeEchoRequest)
+	f.Accept(ipv6.ICMPTypeEchoReply)
 	if err := p.SetICMPFilter(&f); err != nil {
 		t.Fatal(err)
 	}
diff --git a/ipv6/icmp_windows.go b/ipv6/icmp_windows.go
index 510c0d4..9dcfb81 100644
--- a/ipv6/icmp_windows.go
+++ b/ipv6/icmp_windows.go
@@ -8,7 +8,11 @@
 	// TODO(mikio): implement this
 }
 
-func (f *sysICMPv6Filter) set(typ ICMPType, block bool) {
+func (f *sysICMPv6Filter) accept(typ ICMPType) {
+	// TODO(mikio): implement this
+}
+
+func (f *sysICMPv6Filter) block(typ ICMPType) {
 	// TODO(mikio): implement this
 }
 
diff --git a/ipv6/multicast_test.go b/ipv6/multicast_test.go
index 60dea5d..768f404 100644
--- a/ipv6/multicast_test.go
+++ b/ipv6/multicast_test.go
@@ -197,7 +197,7 @@
 
 		var f ipv6.ICMPFilter
 		f.SetAll(true)
-		f.Set(ipv6.ICMPTypeEchoReply, false)
+		f.Accept(ipv6.ICMPTypeEchoReply)
 		if err := p.SetICMPFilter(&f); err != nil {
 			t.Fatal(err)
 		}
diff --git a/ipv6/unicast_test.go b/ipv6/unicast_test.go
index c4699c1..6394965 100644
--- a/ipv6/unicast_test.go
+++ b/ipv6/unicast_test.go
@@ -119,7 +119,7 @@
 
 	var f ipv6.ICMPFilter
 	f.SetAll(true)
-	f.Set(ipv6.ICMPTypeEchoReply, false)
+	f.Accept(ipv6.ICMPTypeEchoReply)
 	if err := p.SetICMPFilter(&f); err != nil {
 		t.Fatal(err)
 	}