Add ping client

ping/cmsg_windows.go

@@ -0,0 +1,46 @@
+package ping
+
+import (
+	"encoding/binary"
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/windows"
+)
+
+const (
+	IPV6_HOPLIMIT   = 21
+	IPV6_TCLASS     = 39
+	IPV6_RECVTCLASS = 40
+)
+
+var (
+	alignedSizeofCmsghdr = (sizeofCmsghdr + cmsgAlignTo - 1) & ^(cmsgAlignTo - 1)
+	sizeofCmsghdr        = int(unsafe.Sizeof(windows.WSACMSGHDR{}))
+	cmsgAlignTo          = int(unsafe.Sizeof(uintptr(0)))
+)
+
+func cmsgAlign(n int) int {
+	return (n + cmsgAlignTo - 1) & ^(cmsgAlignTo - 1)
+}
+
+func parseIPv6ControlMessage(cmsg []byte) (*ipv6.ControlMessage, error) {
+	var controlMessage ipv6.ControlMessage
+	for len(cmsg) >= sizeofCmsghdr {
+		cmsghdr := (*windows.WSACMSGHDR)(unsafe.Pointer(unsafe.SliceData(cmsg)))
+		msgLen := int(cmsghdr.Len)
+		msgSize := cmsgAlign(msgLen)
+		if msgLen < sizeofCmsghdr || msgSize > len(cmsg) {
+			return nil, fmt.Errorf("invalid control message length %d", cmsghdr.Len)
+		}
+		switch cmsghdr.Type {
+		case IPV6_TCLASS:
+			controlMessage.TrafficClass = int(binary.NativeEndian.Uint32(cmsg[alignedSizeofCmsghdr : alignedSizeofCmsghdr+4]))
+		case IPV6_HOPLIMIT:
+			controlMessage.HopLimit = int(binary.NativeEndian.Uint32(cmsg[alignedSizeofCmsghdr : alignedSizeofCmsghdr+4]))
+		}
+		cmsg = cmsg[msgSize:]
+	}
+	return &controlMessage, nil
+}