net: dsa: sja1105: Build a minimal understanding of meta frames

Meta frames are sent on the CPU port by the switch if RX timestamping is
enabled. They contain a partial timestamp of the previous frame.

They are Ethernet frames with the Ethernet header constructed out of:

- SJA1105_META_DMAC
- SJA1105_META_SMAC
- ETH_P_SJA1105_META

The Ethernet payload will be decoded in a follow-up patch.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/dsa/sja1105.h b/include/linux/dsa/sja1105.h
index 5a956f3..cc4a909 100644 (file)
--- a/include/linux/dsa/sja1105.h
+++ b/include/linux/dsa/sja1105.h
@@ -12,6 +12,7 @@
 #include <net/dsa.h>
 
 #define ETH_P_SJA1105                          ETH_P_DSA_8021Q
+#define ETH_P_SJA1105_META                     0x0008
 
 /* IEEE 802.3 Annex 57A: Slow Protocols PDUs (01:80:C2:xx:xx:xx) */
 #define SJA1105_LINKLOCAL_FILTER_A             0x0180C2000000ull
@@ -20,6 +21,16 @@
 #define SJA1105_LINKLOCAL_FILTER_B             0x011B19000000ull
 #define SJA1105_LINKLOCAL_FILTER_B_MASK                0xFFFFFF000000ull
 
+/* Source and Destination MAC of follow-up meta frames.
+ * Whereas the choice of SMAC only affects the unique identification of the
+ * switch as sender of meta frames, the DMAC must be an address that is present
+ * in the DSA master port's multicast MAC filter.
+ * 01-80-C2-00-00-0E is a good choice for this, as all profiles of IEEE 1588
+ * over L2 use this address for some purpose already.
+ */
+#define SJA1105_META_SMAC                      0x222222222222ull
+#define SJA1105_META_DMAC                      0x0180C200000Eull
+
 struct sja1105_port {
        struct dsa_port *dp;
        bool hwts_tx_en;

diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index cd8e0bf..0beb525 100644 (file)
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -22,6 +22,21 @@ static inline bool sja1105_is_link_local(const struct sk_buff *skb)
        return false;
 }
 
+static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
+{
+       const struct ethhdr *hdr = eth_hdr(skb);
+       u64 smac = ether_addr_to_u64(hdr->h_source);
+       u64 dmac = ether_addr_to_u64(hdr->h_dest);
+
+       if (smac != SJA1105_META_SMAC)
+               return false;
+       if (dmac != SJA1105_META_DMAC)
+               return false;
+       if (ntohs(hdr->h_proto) != ETH_P_SJA1105_META)
+               return false;
+       return true;
+}
+
 /* This is the first time the tagger sees the frame on RX.
  * Figure out if we can decode it, and if we can, annotate skb->cb with how we
  * plan to do that, so we don't need to check again in the rcv function.