[PATCH v4 net-next 13/17] net: dsa: sja1105: Receive and decode meta frames

From: Vladimir Oltean
Date: Sat Jun 08 2019 - 08:10:18 EST


This adds support in the tagger for understanding the source port and
switch id of meta frames. Their timestamp is also extracted but not
used yet - this needs to be done in a state machine that modifies the
previously received timestampable frame - will be added in a follow-up
patch.

Also take the opportunity to:
- Remove a comment in sja1105_filter made obsolete by e8d67fa5696e
("net: dsa: sja1105: Don't store frame type in skb->cb")
- Reorder the checks in sja1105_filter to optimize for the most likely
scenario first: regular traffic.

Signed-off-by: Vladimir Oltean <olteanv@xxxxxxxxx>
---
Changes in v4:

See last paragraph from the commit message.

Changes in v3:

Split from previous 09/10 patch (no functional changes).

Changes in v2:

None.

net/dsa/tag_sja1105.c | 44 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 094711ced5c0..5b51e96130c7 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -24,6 +24,36 @@ static inline bool sja1105_is_link_local(const struct sk_buff *skb)
return false;
}

+struct sja1105_meta {
+ u64 tstamp;
+ u64 dmac_byte_4;
+ u64 dmac_byte_3;
+ u64 source_port;
+ u64 switch_id;
+};
+
+static void sja1105_meta_unpack(const struct sk_buff *skb,
+ struct sja1105_meta *meta)
+{
+ u8 *buf = skb_mac_header(skb) + ETH_HLEN;
+
+ /* UM10944.pdf section 4.2.17 AVB Parameters:
+ * Structure of the meta-data follow-up frame.
+ * It is in network byte order, so there are no quirks
+ * while unpacking the meta frame.
+ *
+ * Also SJA1105 E/T only populates bits 23:0 of the timestamp
+ * whereas P/Q/R/S does 32 bits. Since the structure is the
+ * same and the E/T puts zeroes in the high-order byte, use
+ * a unified unpacking command for both device series.
+ */
+ packing(buf, &meta->tstamp, 31, 0, 4, UNPACK, 0);
+ packing(buf + 4, &meta->dmac_byte_4, 7, 0, 1, UNPACK, 0);
+ packing(buf + 5, &meta->dmac_byte_3, 7, 0, 1, UNPACK, 0);
+ packing(buf + 6, &meta->source_port, 7, 0, 1, UNPACK, 0);
+ packing(buf + 7, &meta->switch_id, 7, 0, 1, UNPACK, 0);
+}
+
static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
{
const struct ethhdr *hdr = eth_hdr(skb);
@@ -40,14 +70,15 @@ static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
}

/* 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.
+ * Figure out if we can decode it.
*/
static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
{
+ if (!dsa_port_is_vlan_filtering(dev->dsa_ptr))
+ return true;
if (sja1105_is_link_local(skb))
return true;
- if (!dsa_port_is_vlan_filtering(dev->dsa_ptr))
+ if (sja1105_is_meta_frame(skb))
return true;
return false;
}
@@ -83,16 +114,19 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
struct net_device *netdev,
struct packet_type *pt)
{
+ struct sja1105_meta meta = {0};
int source_port, switch_id;
struct vlan_ethhdr *hdr;
u16 tpid, vid, tci;
bool is_link_local;
bool is_tagged;
+ bool is_meta;

hdr = vlan_eth_hdr(skb);
tpid = ntohs(hdr->h_vlan_proto);
is_tagged = (tpid == ETH_P_SJA1105);
is_link_local = sja1105_is_link_local(skb);
+ is_meta = sja1105_is_meta_frame(skb);

skb->offload_fwd_mark = 1;

@@ -113,6 +147,10 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
/* Clear the DMAC bytes that were mangled by the switch */
hdr->h_dest[3] = 0;
hdr->h_dest[4] = 0;
+ } else if (is_meta) {
+ sja1105_meta_unpack(skb, &meta);
+ source_port = meta.source_port;
+ switch_id = meta.switch_id;
} else {
return NULL;
}
--
2.17.1