dsa: add support for Trailer tagging format

This adds support for the Trailer switch tagging format.  This is
another tagging that doesn't explicitly mark tagged packets with a
distinct ethertype, so that we need to add a similar hack in the
receive path as for the Original DSA tagging format.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Tested-by: Byron Bradley <byron.bbradley@gmail.com>
Tested-by: Tim Ellis <tim.ellis@mac.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 152 insertions, 0 deletions

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 79bcd76d3f10..505aa14e67fc 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -18,6 +18,10 @@ config NET_DSA_TAG_EDSA
         bool
         default n
 
+config NET_DSA_TAG_TRAILER
+        bool
+        default n
+
 
 # switch drivers
 config NET_DSA_MV88E6XXX
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 7fb6f85a69ed..63d3c44908b0 100644
--- a/net/dsa/Makefile
+++ b/net/dsa/Makefile
@@ -1,6 +1,7 @@
 # tagging formats
 obj-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa.o
 obj-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
+obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
 
 # switch drivers
 obj-$(CONFIG_NET_DSA_MV88E6XXX) += mv88e6xxx.o
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index f8c549281c30..33e99462023a 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -217,6 +217,13 @@ bool dsa_uses_dsa_tags(void *dsa_ptr)
         return !!(ds->tag_protocol == htons(ETH_P_DSA));
 }
 
+bool dsa_uses_trailer_tags(void *dsa_ptr)
+{
+        struct dsa_switch *ds = dsa_ptr;
+
+        return !!(ds->tag_protocol == htons(ETH_P_TRAILER));
+}
+
 
 /* link polling *************************************************************/
 static void dsa_link_poll_work(struct work_struct *ugly)
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 2f1d68c495e8..7063378a1ebf 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -109,5 +109,8 @@ int dsa_xmit(struct sk_buff *skb, struct net_device *dev);
 /* tag_edsa.c */
 int edsa_xmit(struct sk_buff *skb, struct net_device *dev);
 
+/* tag_trailer.c */
+int trailer_xmit(struct sk_buff *skb, struct net_device *dev);
+
 
 #endif
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 8f8868dd4302..37616884b8a9 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -249,6 +249,11 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
                 slave_dev->hard_start_xmit = edsa_xmit;
                 break;
 #endif
+#ifdef CONFIG_NET_DSA_TAG_TRAILER
+        case htons(ETH_P_TRAILER):
+                slave_dev->hard_start_xmit = trailer_xmit;
+                break;
+#endif
         default:
                 BUG();
         }
diff --git a/net/dsa/tag_trailer.c b/net/dsa/tag_trailer.c
new file mode 100644
index 000000000000..d3117764b2c2
--- /dev/null
+++ b/net/dsa/tag_trailer.c
@@ -0,0 +1,130 @@
+/*
+ * net/dsa/tag_trailer.c - Trailer tag format handling
+ * Copyright (c) 2008 Marvell Semiconductor
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include "dsa_priv.h"
+
+int trailer_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+        struct dsa_slave_priv *p = netdev_priv(dev);
+        struct sk_buff *nskb;
+        int padlen;
+        u8 *trailer;
+
+        dev->stats.tx_packets++;
+        dev->stats.tx_bytes += skb->len;
+
+        /*
+         * We have to make sure that the trailer ends up as the very
+         * last 4 bytes of the packet.  This means that we have to pad
+         * the packet to the minimum ethernet frame size, if necessary,
+         * before adding the trailer.
+         */
+        padlen = 0;
+        if (skb->len < 60)
+                padlen = 60 - skb->len;
+
+        nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
+        if (nskb == NULL) {
+                kfree_skb(skb);
+                return NETDEV_TX_OK;
+        }
+        skb_reserve(nskb, NET_IP_ALIGN);
+
+        skb_reset_mac_header(nskb);
+        skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
+        skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
+        skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
+        kfree_skb(skb);
+
+        if (padlen) {
+                u8 *pad = skb_put(nskb, padlen);
+                memset(pad, 0, padlen);
+        }
+
+        trailer = skb_put(nskb, 4);
+        trailer[0] = 0x80;
+        trailer[1] = 1 << p->port;
+        trailer[2] = 0x10;
+        trailer[3] = 0x00;
+
+        nskb->protocol = htons(ETH_P_TRAILER);
+
+        nskb->dev = p->parent->master_netdev;
+        dev_queue_xmit(nskb);
+
+        return NETDEV_TX_OK;
+}
+
+static int trailer_rcv(struct sk_buff *skb, struct net_device *dev,
+                       struct packet_type *pt, struct net_device *orig_dev)
+{
+        struct dsa_switch *ds = dev->dsa_ptr;
+        u8 *trailer;
+        int source_port;
+
+        if (unlikely(ds == NULL))
+                goto out_drop;
+
+        skb = skb_unshare(skb, GFP_ATOMIC);
+        if (skb == NULL)
+                goto out;
+
+        if (skb_linearize(skb))
+                goto out_drop;
+
+        trailer = skb_tail_pointer(skb) - 4;
+        if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
+            (trailer[3] & 0xef) != 0x00 || trailer[3] != 0x00)
+                goto out_drop;
+
+        source_port = trailer[1] & 7;
+        if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
+                goto out_drop;
+
+        pskb_trim_rcsum(skb, skb->len - 4);
+
+        skb->dev = ds->ports[source_port];
+        skb_push(skb, ETH_HLEN);
+        skb->protocol = eth_type_trans(skb, skb->dev);
+
+        skb->dev->last_rx = jiffies;
+        skb->dev->stats.rx_packets++;
+        skb->dev->stats.rx_bytes += skb->len;
+
+        netif_receive_skb(skb);
+
+        return 0;
+
+out_drop:
+        kfree_skb(skb);
+out:
+        return 0;
+}
+
+static struct packet_type trailer_packet_type = {
+        .type   = __constant_htons(ETH_P_TRAILER),
+        .func   = trailer_rcv,
+};
+
+static int __init trailer_init_module(void)
+{
+        dev_add_pack(&trailer_packet_type);
+        return 0;
+}
+module_init(trailer_init_module);
+
+static void __exit trailer_cleanup_module(void)
+{
+        dev_remove_pack(&trailer_packet_type);
+}
+module_exit(trailer_cleanup_module);
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index dae47e7a44d8..b9d85af2dd31 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -193,6 +193,8 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
          */
         if (netdev_uses_dsa_tags(dev))
                 return htons(ETH_P_DSA);
+        if (netdev_uses_trailer_tags(dev))
+                return htons(ETH_P_TRAILER);
 
         if (ntohs(eth->h_proto) >= 1536)
                 return eth->h_proto;