[PATCH v3 net-next 1/3] net: dsa: tag_dsa: Allow forwarding of redirected IGMP traffic

[Tobias Waldekranz]

When receiving an IGMP/MLD frame with a TO_CPU tag, the switch has not
performed any forwarding of it. This means that we should not set the
offload_fwd_mark on the skb, in case a software bridge wants it
forwarded.

This is a port of:

1ed9ec9b08ad ("dsa: Allow forwarding of redirected IGMP traffic")

Which corrected the issue for chips using EDSA tags, but not for those
using regular DSA tags.

Signed-off-by: Tobias Waldekranz <tob...@waldekranz.com>
---
 net/dsa/tag_dsa.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index 63d690a0fca6..af340a4945dc 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -12,6 +12,11 @@
 
 #define DSA_HLEN       4
 
+#define FRAME_TYPE_TO_CPU      0x00
+#define FRAME_TYPE_FORWARD     0x03
+
+#define TO_CPU_CODE_IGMP_MLD_TRAP      0x02
+
 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 {
        struct dsa_port *dp = dsa_slave_to_port(dev);
@@ -61,6 +66,8 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct 
net_device *dev,
        u8 *dsa_header;
        int source_device;
        int source_port;
+       int frame_type;
+       int code;
 
        if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
                return NULL;
@@ -73,8 +80,29 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct 
net_device *dev,
        /*
         * Check that frame type is either TO_CPU or FORWARD.
         */
-       if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
+       frame_type = dsa_header[0] >> 6;
+
+       switch (frame_type) {
+       case FRAME_TYPE_TO_CPU:
+               code = (dsa_header[1] & 0x6) | ((dsa_header[2] >> 4) & 1);
+
+               /*
+                * Mark the frame to never egress on any port of the same switch
+                * unless it's a trapped IGMP/MLD packet, in which case the
+                * bridge might want to forward it.
+                */
+               if (code != TO_CPU_CODE_IGMP_MLD_TRAP)
+                       skb->offload_fwd_mark = 1;
+
+               break;
+
+       case FRAME_TYPE_FORWARD:
+               skb->offload_fwd_mark = 1;
+               break;
+
+       default:
                return NULL;
+       }
 
        /*
         * Determine source device and port.
@@ -132,8 +160,6 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct 
net_device *dev,
                        2 * ETH_ALEN);
        }
 
-       skb->offload_fwd_mark = 1;
-
        return skb;
 }
 
-- 
2.17.1