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wgengine/winnet: invoke some COM methods directly instead of through IDispatch.

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Intermittently in the wild we are seeing failures when calling
`INetworkConnection::GetNetwork`. It is unclear what the root cause is, but what
is clear is that the error is happening inside the object's `IDispatch` invoker
(as opposed to the method implementation itself).

This patch replaces our wrapper for `INetworkConnection::GetNetwork` with an
alternate implementation that directly invokes the method, instead of using
`IDispatch`. I also replaced the implementations of `INetwork::SetCategory` and
`INetwork::GetCategory` while I was there.

This patch is speculative and tightly-scoped so that we could possibly add it
to a dot-release if necessary.

Updates https://github.com/tailscale/tailscale/issues/4134
Updates https://github.com/tailscale/tailscale/issues/6037

Signed-off-by: Aaron Klotz <aaron@tailscale.com>
This commit is contained in:
Aaron Klotz 2022-10-26 14:41:29 -06:00
parent 4021ae6b9d
commit a44687e71f
1 changed files with 54 additions and 18 deletions
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72
wgengine/winnet/winnet.go
View File

@ -9,6 +9,7 @@
import (
"fmt"
"syscall"
"unsafe"
"github.com/go-ole/go-ole"
@ -45,6 +46,23 @@ type INetwork struct {
ole.IDispatch
}
type INetworkVtbl struct {
ole.IDispatchVtbl
GetName uintptr
SetName uintptr
GetDescription uintptr
SetDescription uintptr
GetNetworkId uintptr
GetDomainType uintptr
GetNetworkConnections uintptr
GetTimeCreatedAndConnected uintptr
Get_IsConnectedToInternet uintptr
Get_IsConnected uintptr
GetConnectivity uintptr
GetCategory uintptr
SetCategory uintptr
}
func NewNetworkListManager(c *ole.Connection) (*NetworkListManager, error) {
err := c.Create(CLSID_NetworkListManager)
if err != nil {
@ -124,16 +142,35 @@ func (n *INetwork) GetName() (string, error) {
}
func (n *INetwork) GetCategory() (int32, error) {
v, err := n.CallMethod("GetCategory")
if err != nil {
return 0, err
var result int32
r, _, _ := syscall.SyscallN(
n.VTable().GetCategory,
uintptr(unsafe.Pointer(n)),
uintptr(unsafe.Pointer(&result)),
)
if int32(r) < 0 {
return 0, ole.NewError(r)
}
return v.Value().(int32), err
return result, nil
}
func (n *INetwork) SetCategory(v uint32) error {
_, err := n.CallMethod("SetCategory", v)
return err
func (n *INetwork) SetCategory(v int32) error {
r, _, _ := syscall.SyscallN(
n.VTable().SetCategory,
uintptr(unsafe.Pointer(n)),
uintptr(v),
)
if int32(r) < 0 {
return ole.NewError(r)
}
return nil
}
func (n *INetwork) VTable() *INetworkVtbl {
return (*INetworkVtbl)(unsafe.Pointer(n.RawVTable))
}
func (v *INetworkConnection) VTable() *INetworkConnectionVtbl {
@ -141,17 +178,16 @@ func (v *INetworkConnection) VTable() *INetworkConnectionVtbl {
}
func (v *INetworkConnection) GetNetwork() (*INetwork, error) {
nraw, err := v.CallMethod("GetNetwork")
if err != nil {
return nil, err
var result *INetwork
r, _, _ := syscall.SyscallN(
v.VTable().GetNetwork,
uintptr(unsafe.Pointer(v)),
uintptr(unsafe.Pointer(&result)),
)
if int32(r) < 0 {
return nil, ole.NewError(r)
}
n := nraw.ToIDispatch()
if n == nil {
return nil, fmt.Errorf("GetNetwork: nil IDispatch")
}
if err != nil {
return nil, err
}
return (*INetwork)(unsafe.Pointer(n)), nil
return result, nil
}