[PATCH] Updating the GEM MAC IP to properly filter out the multicast addresses

["Wasim, Bilal" <Bilal_Wasim@mentor.com>]

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[PATCH] Updating the GEM MAC IP to properly filter out the multicast
addresses. The current code makes a bad assumption that the most-significant
byte of the MAC address is used to determine if the address is multicast or
unicast, but in reality only a single bit is used to determine this. This
caused IPv6 to not work.. Fix is now in place and has been tested with
ZCU102-A53 / IPv6 on a TAP interface. Works well..

Signed-off-by: Bilal Wasim <bilal_wasim@mentor.com>
---
hw/net/cadence_gem.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
index b8be73d..f8bcbb3 100644
--- a/hw/net/cadence_gem.c
+++ b/hw/net/cadence_gem.c
@@ -315,6 +315,12 @@
 #define GEM_MODID_VALUE 0x00020118
+/* IEEE has specified that the most significant bit of the most significant byte be used for
+ * distinguishing between Unicast and Multicast addresses.
+ * If its a 1, that means multicast, 0 means unicast.   */
+#define IS_MULTICAST(address)           (((address[0] & 0x01) == 0x01) ? 1 : 0)
+#define IS_UNICAST(address)             (!IS_MULTICAST(address))
+
static inline uint64_t tx_desc_get_buffer(CadenceGEMState *s, uint32_t *desc)
{
     uint64_t ret = desc[0];
@@ -690,21 +696,21 @@ static int gem_mac_address_filter(CadenceGEMState *s, const uint8_t *packet)
     }
     /* Accept packets -w- hash match? */
-    if ((packet[0] == 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
-        (packet[0] != 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
+    if ((IS_MULTICAST(packet) && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
+        (IS_UNICAST(packet)   && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
         unsigned hash_index;
         hash_index = calc_mac_hash(packet);
         if (hash_index < 32) {
             if (s->regs[GEM_HASHLO] & (1<<hash_index)) {
-                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
-                                           GEM_RX_UNICAST_HASH_ACCEPT;
+                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
+                                              GEM_RX_UNICAST_HASH_ACCEPT;
             }
         } else {
             hash_index -= 32;
             if (s->regs[GEM_HASHHI] & (1<<hash_index)) {
-                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
-                                           GEM_RX_UNICAST_HASH_ACCEPT;
+                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
+                                              GEM_RX_UNICAST_HASH_ACCEPT;
             }
         }
     }
--
2.9.3


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