NetworkPkg/HttpBootDxe: Correctly uninstall HttpBootCallbackProtocol

The existing HttpBootUninstallCallback was passing the wrong handle (the
PrivateData root controller handle, not the correct child IPv4 or IPv6
NIC controller handle; cf HttpBootInstallCallback for matching logic) and
was also passing the address of a pointer to the interface to be removed
rather than the pointer itself, so always failed with EFI_NOT_FOUND.

This resulted in the prior behaviour that if multiple HTTP boot attempts
were made, on the second and subsequent attempts the instance of this
protocol installed by the first attempt would be re-used. As long as only
one driver using the protocol is installed, this ends up producing the
same results as if the protocol had been uninstalled then reinstalled
correctly.

After this commit, the protocol is installed at the start of an HTTP boot
attempt and uninstalled it at the end of it (assuming nothing else has
accessed the protocol in a way which blocks the uninstall).

It might seem attractive to add an ASSERT to confirm when debugging
that the uninstall succeeds as expected, but this is recommended against
because uninstallation of protocol interfaces is allowed to fail under
the UEFI model:
https://edk2.groups.io/g/devel/message/117469.
An ASSERT could therefore arise from a sequence of events which is
perfectly valid - or at least is out of the control of this driver.

Signed-off-by: Mike Beaton <[email protected]>

NetworkPkg/HttpBootDxe/HttpBootImpl.c

@@ -77,11 +77,19 @@ HttpBootUninstallCallback (
   IN HTTP_BOOT_PRIVATE_DATA  *Private
   )
 {
+  EFI_HANDLE  ControllerHandle;
+
   if (Private->HttpBootCallback == &Private->LoadFileCallback) {
+    if (!Private->UsingIpv6) {
+      ControllerHandle = Private->Ip4Nic->Controller;
+    } else {
+      ControllerHandle = Private->Ip6Nic->Controller;
+    }
+
     gBS->UninstallProtocolInterface (
-           Private->Controller,
+           ControllerHandle,
            &gEfiHttpBootCallbackProtocolGuid,
-           &Private->HttpBootCallback
+           Private->HttpBootCallback
            );
     Private->HttpBootCallback = NULL;
   }