[PATCH V2] efinet: handle get_status() on buggy firmware properly

[Josef Bacik <jbacik@fb.com>]

The EFI spec indicates that get_status() should return the address of the buffer
we passed into transmit to indicate the the buffer was transmitted.  However we
have boxes where the firmware returns some arbitrary address instead, which
makes grub think that we've not sent anything.  So since we have the SNP stuff
opened in exclusive mode just assume any non-NULL txbuf means that our transmit
occurred properly.  This makes grub able to do its networking stuff properly on
our broken firmware.  Thanks,

cc: Peter Jones <pjones@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
---
V1->V2:
-updated the changelog to be more clear about what we are fixing.
-added a comment to the code to indicate why it is safe to only check for
 non-NULL txbufs and why we need to do it.

 grub-core/net/drivers/efi/efinet.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/grub-core/net/drivers/efi/efinet.c b/grub-core/net/drivers/efi/efinet.c
index f27a117..692d5ad 100644
--- a/grub-core/net/drivers/efi/efinet.c
+++ b/grub-core/net/drivers/efi/efinet.c
@@ -47,19 +47,19 @@ send_card_buffer (struct grub_net_card *dev,
 	if (st != GRUB_EFI_SUCCESS)
 	  return grub_error (GRUB_ERR_IO,
 			     N_("couldn't send network packet"));
-	if (txbuf == dev->txbuf)
+	/*
+	   Some buggy firmware could return an arbitrary address instead of the
+	   txbuf address we trasmitted, so just check that txbuf is non NULL
+	   for success.  This is ok because we open the SNP protocol in
+	   exclusive mode so we know we're the only ones transmitting on this
+	   box and since we only transmit one packet at a time we know our
+	   transmit was successfull.
+	 */
+	if (txbuf)
 	  {
 	    dev->txbusy = 0;
 	    break;
 	  }
-	if (txbuf)
-	  {
-	    st = efi_call_7 (net->transmit, net, 0, dev->last_pkt_size,
-			     dev->txbuf, NULL, NULL, NULL);
-	    if (st != GRUB_EFI_SUCCESS)
-	      return grub_error (GRUB_ERR_IO,
-				 N_("couldn't send network packet"));
-	  }
 	if (limit_time < grub_get_time_ms ())
 	  return grub_error (GRUB_ERR_TIMEOUT,
 			     N_("couldn't send network packet"));
@@ -84,8 +84,9 @@ send_card_buffer (struct grub_net_card *dev,
      we run in the GRUB_ERR_TIMEOUT case above.
      Perhaps a timeout in the FW has discarded the recycle buffer.
    */
+  txbuf = NULL;
   st = efi_call_3 (net->get_status, net, 0, &txbuf);
-  dev->txbusy = !(st == GRUB_EFI_SUCCESS && txbuf == dev->txbuf);
+  dev->txbusy = !(st == GRUB_EFI_SUCCESS && txbuf);
 
   return GRUB_ERR_NONE;
 }
-- 
1.8.1