windows: add iphlpapi routing functions

NotifyRouteChange2 registers to be notified for changes to IP route
entries. Call GetIpForwardEntry2 on received row to retrieve complete
information.

GetIpForwardTable2 retrieves the full routing table.
FreeMibTable frees the buffer allocated by the functions that return
tables of network interfaces, addresses, and routes.

Change-Id: I9fba75f1f728661e45dc3092e35eb9099b0570dd
Reviewed-on: https://go-review.googlesource.com/c/sys/+/695195
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

windows/syscall_windows.go

@@ -892,8 +892,12 @@ const socket_error = uintptr(^uint32(0))
 //sys	MultiByteToWideChar(codePage uint32, dwFlags uint32, str *byte, nstr int32, wchar *uint16, nwchar int32) (nwrite int32, err error) = kernel32.MultiByteToWideChar
 //sys	getBestInterfaceEx(sockaddr unsafe.Pointer, pdwBestIfIndex *uint32) (errcode error) = iphlpapi.GetBestInterfaceEx
 //sys   GetIfEntry2Ex(level uint32, row *MibIfRow2) (errcode error) = iphlpapi.GetIfEntry2Ex
+//sys   GetIpForwardEntry2(row *MibIpForwardRow2) (errcode error) = iphlpapi.GetIpForwardEntry2
+//sys   GetIpForwardTable2(family uint16, table **MibIpForwardTable2) (errcode error) = iphlpapi.GetIpForwardTable2
 //sys   GetUnicastIpAddressEntry(row *MibUnicastIpAddressRow) (errcode error) = iphlpapi.GetUnicastIpAddressEntry
+//sys   FreeMibTable(memory unsafe.Pointer) = iphlpapi.FreeMibTable
 //sys   NotifyIpInterfaceChange(family uint16, callback uintptr, callerContext unsafe.Pointer, initialNotification bool, notificationHandle *Handle) (errcode error) = iphlpapi.NotifyIpInterfaceChange
+//sys   NotifyRouteChange2(family uint16, callback uintptr, callerContext unsafe.Pointer, initialNotification bool, notificationHandle *Handle) (errcode error) = iphlpapi.NotifyRouteChange2
 //sys   NotifyUnicastIpAddressChange(family uint16, callback uintptr, callerContext unsafe.Pointer, initialNotification bool, notificationHandle *Handle) (errcode error) = iphlpapi.NotifyUnicastIpAddressChange
 //sys   CancelMibChangeNotify2(notificationHandle Handle) (errcode error) = iphlpapi.CancelMibChangeNotify2
 
@@ -916,6 +920,17 @@ type RawSockaddrInet6 struct {
 	Scope_id uint32
 }
 
+// RawSockaddrInet is a union that contains an IPv4, an IPv6 address, or an address family. See
+// https://learn.microsoft.com/en-us/windows/win32/api/ws2ipdef/ns-ws2ipdef-sockaddr_inet.
+//
+// A [*RawSockaddrInet] may be converted to a [*RawSockaddrInet4] or [*RawSockaddrInet6] using
+// unsafe, depending on the address family.
+type RawSockaddrInet struct {
+	Family uint16
+	Port   uint16
+	Data   [6]uint32
+}
+
 type RawSockaddr struct {
 	Family uint16
 	Data   [14]int8

windows/types_windows.go

@@ -2320,6 +2320,82 @@ type MibIfRow2 struct {
 	OutQLen                     uint64
 }
 
+// IP_ADDRESS_PREFIX stores an IP address prefix. See
+// https://learn.microsoft.com/en-us/windows/win32/api/netioapi/ns-netioapi-ip_address_prefix.
+type IpAddressPrefix struct {
+	Prefix       RawSockaddrInet
+	PrefixLength uint8
+}
+
+// NL_ROUTE_ORIGIN enumeration from nldef.h or
+// https://learn.microsoft.com/en-us/windows/win32/api/nldef/ne-nldef-nl_route_origin.
+const (
+	NlroManual              = 0
+	NlroWellKnown           = 1
+	NlroDHCP                = 2
+	NlroRouterAdvertisement = 3
+	Nlro6to4                = 4
+)
+
+// NL_ROUTE_ORIGIN enumeration from nldef.h or
+// https://learn.microsoft.com/en-us/windows/win32/api/nldef/ne-nldef-nl_route_protocol.
+const (
+	MIB_IPPROTO_OTHER             = 1
+	MIB_IPPROTO_LOCAL             = 2
+	MIB_IPPROTO_NETMGMT           = 3
+	MIB_IPPROTO_ICMP              = 4
+	MIB_IPPROTO_EGP               = 5
+	MIB_IPPROTO_GGP               = 6
+	MIB_IPPROTO_HELLO             = 7
+	MIB_IPPROTO_RIP               = 8
+	MIB_IPPROTO_IS_IS             = 9
+	MIB_IPPROTO_ES_IS             = 10
+	MIB_IPPROTO_CISCO             = 11
+	MIB_IPPROTO_BBN               = 12
+	MIB_IPPROTO_OSPF              = 13
+	MIB_IPPROTO_BGP               = 14
+	MIB_IPPROTO_IDPR              = 15
+	MIB_IPPROTO_EIGRP             = 16
+	MIB_IPPROTO_DVMRP             = 17
+	MIB_IPPROTO_RPL               = 18
+	MIB_IPPROTO_DHCP              = 19
+	MIB_IPPROTO_NT_AUTOSTATIC     = 10002
+	MIB_IPPROTO_NT_STATIC         = 10006
+	MIB_IPPROTO_NT_STATIC_NON_DOD = 10007
+)
+
+// MIB_IPFORWARD_ROW2 stores information about an IP route entry. See
+// https://learn.microsoft.com/en-us/windows/win32/api/netioapi/ns-netioapi-mib_ipforward_row2.
+type MibIpForwardRow2 struct {
+	InterfaceLuid        uint64
+	InterfaceIndex       uint32
+	DestinationPrefix    IpAddressPrefix
+	NextHop              RawSockaddrInet
+	SitePrefixLength     uint8
+	ValidLifetime        uint32
+	PreferredLifetime    uint32
+	Metric               uint32
+	Protocol             uint32
+	Loopback             uint8
+	AutoconfigureAddress uint8
+	Publish              uint8
+	Immortal             uint8
+	Age                  uint32
+	Origin               uint32
+}
+
+// MIB_IPFORWARD_TABLE2 contains a table of IP route entries. See
+// https://learn.microsoft.com/en-us/windows/win32/api/netioapi/ns-netioapi-mib_ipforward_table2.
+type MibIpForwardTable2 struct {
+	NumEntries uint32
+	Table      [1]MibIpForwardRow2
+}
+
+// Rows returns the IP route entries in the table.
+func (t *MibIpForwardTable2) Rows() []MibIpForwardRow2 {
+	return unsafe.Slice(&t.Table[0], t.NumEntries)
+}
+
 // MIB_UNICASTIPADDRESS_ROW stores information about a unicast IP address. See
 // https://learn.microsoft.com/en-us/windows/win32/api/netioapi/ns-netioapi-mib_unicastipaddress_row.
 type MibUnicastIpAddressRow struct {

windows/zsyscall_windows.go

@@ -182,13 +182,17 @@ var (
 	procDwmGetWindowAttribute                                = moddwmapi.NewProc("DwmGetWindowAttribute")
 	procDwmSetWindowAttribute                                = moddwmapi.NewProc("DwmSetWindowAttribute")
 	procCancelMibChangeNotify2                               = modiphlpapi.NewProc("CancelMibChangeNotify2")
+	procFreeMibTable                                         = modiphlpapi.NewProc("FreeMibTable")
 	procGetAdaptersAddresses                                 = modiphlpapi.NewProc("GetAdaptersAddresses")
 	procGetAdaptersInfo                                      = modiphlpapi.NewProc("GetAdaptersInfo")
 	procGetBestInterfaceEx                                   = modiphlpapi.NewProc("GetBestInterfaceEx")
 	procGetIfEntry                                           = modiphlpapi.NewProc("GetIfEntry")
 	procGetIfEntry2Ex                                        = modiphlpapi.NewProc("GetIfEntry2Ex")
+	procGetIpForwardEntry2                                   = modiphlpapi.NewProc("GetIpForwardEntry2")
+	procGetIpForwardTable2                                   = modiphlpapi.NewProc("GetIpForwardTable2")
 	procGetUnicastIpAddressEntry                             = modiphlpapi.NewProc("GetUnicastIpAddressEntry")
 	procNotifyIpInterfaceChange                              = modiphlpapi.NewProc("NotifyIpInterfaceChange")
+	procNotifyRouteChange2                                   = modiphlpapi.NewProc("NotifyRouteChange2")
 	procNotifyUnicastIpAddressChange                         = modiphlpapi.NewProc("NotifyUnicastIpAddressChange")
 	procAddDllDirectory                                      = modkernel32.NewProc("AddDllDirectory")
 	procAssignProcessToJobObject                             = modkernel32.NewProc("AssignProcessToJobObject")
@@ -1624,6 +1628,11 @@ func CancelMibChangeNotify2(notificationHandle Handle) (errcode error) {
 	return
 }
 
+func FreeMibTable(memory unsafe.Pointer) {
+	syscall.SyscallN(procFreeMibTable.Addr(), uintptr(memory))
+	return
+}
+
 func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) {
 	r0, _, _ := syscall.SyscallN(procGetAdaptersAddresses.Addr(), uintptr(family), uintptr(flags), uintptr(reserved), uintptr(unsafe.Pointer(adapterAddresses)), uintptr(unsafe.Pointer(sizePointer)))
 	if r0 != 0 {
@@ -1664,6 +1673,22 @@ func GetIfEntry2Ex(level uint32, row *MibIfRow2) (errcode error) {
 	return
 }
 
+func GetIpForwardEntry2(row *MibIpForwardRow2) (errcode error) {
+	r0, _, _ := syscall.SyscallN(procGetIpForwardEntry2.Addr(), uintptr(unsafe.Pointer(row)))
+	if r0 != 0 {
+		errcode = syscall.Errno(r0)
+	}
+	return
+}
+
+func GetIpForwardTable2(family uint16, table **MibIpForwardTable2) (errcode error) {
+	r0, _, _ := syscall.SyscallN(procGetIpForwardTable2.Addr(), uintptr(family), uintptr(unsafe.Pointer(table)))
+	if r0 != 0 {
+		errcode = syscall.Errno(r0)
+	}
+	return
+}
+
 func GetUnicastIpAddressEntry(row *MibUnicastIpAddressRow) (errcode error) {
 	r0, _, _ := syscall.SyscallN(procGetUnicastIpAddressEntry.Addr(), uintptr(unsafe.Pointer(row)))
 	if r0 != 0 {
@@ -1684,6 +1709,18 @@ func NotifyIpInterfaceChange(family uint16, callback uintptr, callerContext unsa
 	return
 }
 
+func NotifyRouteChange2(family uint16, callback uintptr, callerContext unsafe.Pointer, initialNotification bool, notificationHandle *Handle) (errcode error) {
+	var _p0 uint32
+	if initialNotification {
+		_p0 = 1
+	}
+	r0, _, _ := syscall.SyscallN(procNotifyRouteChange2.Addr(), uintptr(family), uintptr(callback), uintptr(callerContext), uintptr(_p0), uintptr(unsafe.Pointer(notificationHandle)))
+	if r0 != 0 {
+		errcode = syscall.Errno(r0)
+	}
+	return
+}
+
 func NotifyUnicastIpAddressChange(family uint16, callback uintptr, callerContext unsafe.Pointer, initialNotification bool, notificationHandle *Handle) (errcode error) {
 	var _p0 uint32
 	if initialNotification {