[snp] Allocate additional padding for receive buffers

Some SNP implementations (observed with a wifi adapter in a Dell
Latitude 3440 laptop) seem to require additional space in the
allocated receive buffers, otherwise full-length packets will be
silently dropped.

The EDK2 MnpDxe driver happens to allocate an additional 8 bytes of
padding (4 for a VLAN tag, 4 for the Ethernet frame checksum).  Match
this behaviour since drivers are very likely to have been tested
against MnpDxe.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/drivers/net/efi/snpnet.c b/src/drivers/net/efi/snpnet.c
index 3b09d491819598845faefd35b99ab3e93f08554b..c66aa7d28d3a19ec512a05c84f04681fe0eafc5d 100644 (file)
--- a/src/drivers/net/efi/snpnet.c
+++ b/src/drivers/net/efi/snpnet.c
@@ -71,6 +71,19 @@ struct snp_nic {
 /** Delay between each initialisation retry */
 #define SNP_INITIALIZE_RETRY_DELAY_MS 10
 
+/** Additional padding for receive buffers
+ *
+ * Some SNP implementations seem to require additional space in the
+ * allocated receive buffers, otherwise full-length packets will be
+ * silently dropped.
+ *
+ * The EDK2 MnpDxe driver happens to allocate an additional 8 bytes of
+ * padding (4 for a VLAN tag, 4 for the Ethernet frame checksum).
+ * Match this behaviour since drivers are very likely to have been
+ * tested against MnpDxe.
+ */
+#define SNP_RX_PAD 8
+
 /**
  * Format SNP MAC address (for debugging)
  *
@@ -246,7 +259,7 @@ static void snpnet_poll_rx ( struct net_device *netdev ) {
 
                /* Allocate buffer, if required */
                if ( ! snp->rxbuf ) {
-                       snp->rxbuf = alloc_iob ( snp->mtu );
+                       snp->rxbuf = alloc_iob ( snp->mtu + SNP_RX_PAD );
                        if ( ! snp->rxbuf ) {
                                /* Leave for next poll */
                                break;