go.net/ipv6: make it work with Go 1.1

This CL makes use of built-in syscall stuff to allow go.net/ipv6
to work together with Go 1.1. Also it's able to improve the package
without churning the Go standard library.

Fixes golang/go#6548.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/15040044

ipv6/sockopt_rfc3542_unix.go

diff --git a/ipv6/sockopt_rfc3542_unix.go b/ipv6/sockopt_rfc3542_unix.go
index 463f426..da9111c 100644
--- a/ipv6/sockopt_rfc3542_unix.go
+++ b/ipv6/sockopt_rfc3542_unix.go
@@ -8,41 +8,83 @@
 
 import (
 	"os"
-	"syscall"
+	"unsafe"
 )
 
 func ipv6ReceiveTrafficClass(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVTCLASS)
-	if err != nil {
+	var v int32
+	l := sysSockoptLen(4)
+	if err := getsockopt(fd, ianaProtocolIPv6, sysSockoptReceiveTrafficClass, uintptr(unsafe.Pointer(&v)), &l); err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
 	return v == 1, nil
 }
 
 func setIPv6ReceiveTrafficClass(fd int, v bool) error {
-	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVTCLASS, boolint(v)))
+	vv := int32(boolint(v))
+	return os.NewSyscallError("setsockopt", setsockopt(fd, ianaProtocolIPv6, sysSockoptReceiveTrafficClass, uintptr(unsafe.Pointer(&vv)), 4))
 }
 
 func ipv6ReceiveHopLimit(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVHOPLIMIT)
-	if err != nil {
+	var v int32
+	l := sysSockoptLen(4)
+	if err := getsockopt(fd, ianaProtocolIPv6, sysSockoptReceiveHopLimit, uintptr(unsafe.Pointer(&v)), &l); err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
 	return v == 1, nil
 }
 
 func setIPv6ReceiveHopLimit(fd int, v bool) error {
-	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVHOPLIMIT, boolint(v)))
+	vv := int32(boolint(v))
+	return os.NewSyscallError("setsockopt", setsockopt(fd, ianaProtocolIPv6, sysSockoptReceiveHopLimit, uintptr(unsafe.Pointer(&vv)), 4))
 }
 
 func ipv6ReceivePacketInfo(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVPKTINFO)
-	if err != nil {
+	var v int32
+	l := sysSockoptLen(4)
+	if err := getsockopt(fd, ianaProtocolIPv6, sysSockoptReceivePacketInfo, uintptr(unsafe.Pointer(&v)), &l); err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
 	return v == 1, nil
 }
 
 func setIPv6ReceivePacketInfo(fd int, v bool) error {
-	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd, ianaProtocolIPv6, syscall.IPV6_RECVPKTINFO, boolint(v)))
+	vv := int32(boolint(v))
+	return os.NewSyscallError("setsockopt", setsockopt(fd, ianaProtocolIPv6, sysSockoptReceivePacketInfo, uintptr(unsafe.Pointer(&vv)), 4))
+}
+
+func ipv6PathMTU(fd int) (int, error) {
+	var v sysMTUInfo
+	l := sysSockoptLen(sysSizeofMTUInfo)
+	if err := getsockopt(fd, ianaProtocolIPv6, sysSockoptPathMTU, uintptr(unsafe.Pointer(&v)), &l); err != nil {
+		return 0, os.NewSyscallError("getsockopt", err)
+	}
+	return int(v.MTU), nil
+}
+
+func ipv6ReceivePathMTU(fd int) (bool, error) {
+	var v int32
+	l := sysSockoptLen(4)
+	if err := getsockopt(fd, ianaProtocolIPv6, sysSockoptReceivePathMTU, uintptr(unsafe.Pointer(&v)), &l); err != nil {
+		return false, os.NewSyscallError("getsockopt", err)
+	}
+	return v == 1, nil
+}
+
+func setIPv6ReceivePathMTU(fd int, v bool) error {
+	vv := int32(boolint(v))
+	return os.NewSyscallError("setsockopt", setsockopt(fd, ianaProtocolIPv6, sysSockoptReceivePathMTU, uintptr(unsafe.Pointer(&vv)), 4))
+}
+
+func ipv6ICMPFilter(fd int) (*ICMPFilter, error) {
+	var v ICMPFilter
+	l := sysSockoptLen(sysSizeofICMPFilter)
+	if err := getsockopt(fd, ianaProtocolIPv6ICMP, sysSockoptICMPFilter, uintptr(unsafe.Pointer(&v.sysICMPFilter)), &l); err != nil {
+		return nil, os.NewSyscallError("getsockopt", err)
+	}
+	return &v, nil
+}
+
+func setIPv6ICMPFilter(fd int, f *ICMPFilter) error {
+	return os.NewSyscallError("setsockopt", setsockopt(fd, ianaProtocolIPv6ICMP, sysSockoptICMPFilter, uintptr(unsafe.Pointer(&f.sysICMPFilter)), sysSizeofICMPFilter))
 }