[BRIDGE]: use llc for receiving STP packets

Use LLC for the receive path of Spanning Tree Protocol packets.
This allows link local multicast packets to be received by
other protocols (if they care), and uses the existing LLC
code to get STP packets back into bridge code.

The bridge multicast address is also checked, so bridges using
other link local multicast addresses are ignored. This allows
for use of different multicast addresses to define separate STP
domains.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 18 deletions

diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index c3da01cc6a6f..a99e90e20952 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -15,6 +15,9 @@
 
 #include <linux/kernel.h>
 #include <linux/netfilter_bridge.h>
+#include <linux/etherdevice.h>
+#include <linux/llc.h>
+#include <net/llc_pdu.h>
 
 #include "br_private.h"
 #include "br_private_stp.h"
@@ -130,42 +133,54 @@ void br_send_tcn_bpdu(struct net_bridge_port *p)
         br_send_bpdu(p, buf, 7);
 }
 
-static const unsigned char header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
-
-/* NO locks, but rcu_read_lock (preempt_disabled)  */
-int br_stp_handle_bpdu(struct sk_buff *skb)
+/*
+ * Called from llc.
+ *
+ * NO locks, but rcu_read_lock (preempt_disabled)
+ */
+int br_stp_rcv(struct sk_buff *skb, struct net_device *dev,
+               struct packet_type *pt, struct net_device *orig_dev)
 {
-        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
+        const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
+        const unsigned char *dest = eth_hdr(skb)->h_dest;
+        struct net_bridge_port *p = rcu_dereference(dev->br_port);
         struct net_bridge *br;
-        unsigned char *buf;
+        const unsigned char *buf;
 
         if (!p)
                 goto err;
 
-        br = p->br;
-        spin_lock(&br->lock);
+        if (pdu->ssap != LLC_SAP_BSPAN
+            || pdu->dsap != LLC_SAP_BSPAN
+            || pdu->ctrl_1 != LLC_PDU_TYPE_U)
+                goto err;
 
-        if (p->state == BR_STATE_DISABLED || !(br->dev->flags & IFF_UP))
-                goto out;
+        if (!pskb_may_pull(skb, 4))
+                goto err;
+
+        /* compare of protocol id and version */
+        buf = skb->data;
+        if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
+                goto err;
 
-        /* insert into forwarding database after filtering to avoid spoofing */
-        br_fdb_update(br, p, eth_hdr(skb)->h_source);
+        br = p->br;
+        spin_lock(&br->lock);
 
-        if (!br->stp_enabled)
+        if (p->state == BR_STATE_DISABLED
+            || !br->stp_enabled
+            || !(br->dev->flags & IFF_UP))
                 goto out;
 
-        /* need at least the 802 and STP headers */
-        if (!pskb_may_pull(skb, sizeof(header)+1) ||
-            memcmp(skb->data, header, sizeof(header)))
+        if (compare_ether_addr(dest, bridge_ula) != 0)
                 goto out;
 
-        buf = skb_pull(skb, sizeof(header));
+        buf = skb_pull(skb, 3);
 
         if (buf[0] == BPDU_TYPE_CONFIG) {
                 struct br_config_bpdu bpdu;
 
                 if (!pskb_may_pull(skb, 32))
-                    goto out;
+                        goto out;
 
                 buf = skb->data;
                 bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;