[PATCH] bridge (2.6.5) -- correctl handle up to 256 ports per bridge

[Stephen Hemminger <shemminger@xxxxxxxx>]

Bridge code is limited to 256 ports per bridge because the Spanning
Tree Protocol has limit of one octet for port number.  This code
fixes:
        * bogus unlock in error path when port list is full.
        * passes different error status for out of memory, vs
          port list full.
        * O(n) vs O(n^2) lookup for free port number
        * since port and priority are both limited to one byte
          don't store them as int's
        * makes limit explicit in code

diff -Nru a/net/bridge/br_if.c b/net/bridge/br_if.c
--- a/net/bridge/br_if.c        Thu Apr  1 12:55:31 2004
+++ b/net/bridge/br_if.c        Thu Apr  1 12:55:31 2004
@@ -24,6 +24,9 @@
 #include <asm/uaccess.h>
 #include "br_private.h"
 
+/* Limited to 256 ports because of STP protocol pdu */
+#define  BR_MAX_PORTS  256
+
 static int br_initial_port_cost(struct net_device *dev)
 {
        if (!strncmp(dev->name, "lec", 3))
@@ -126,34 +129,46 @@
        return br;
 }
 
+static int free_port(struct net_bridge *br)
+{
+       int index;
+       struct net_bridge_port *p;
+       long inuse[BR_MAX_PORTS/(sizeof(long)*8)];
+
+       /* find free port number */
+       memset(inuse, 0, sizeof(inuse));
+       list_for_each_entry(p, &br->port_list, list) {
+               set_bit(p->port_no, inuse);
+       }
+
+       index = find_first_zero_bit(inuse, BR_MAX_PORTS);
+       if (index >= BR_MAX_PORTS)
+               return -EXFULL;
+
+       return index;
+}
+
 /* called under bridge lock */
 static struct net_bridge_port *new_nbp(struct net_bridge *br, struct 
net_device *dev)
 {
-       int i;
+       int index;
        struct net_bridge_port *p;
+       
+       index = free_port(br);
+       if (index < 0)
+               return ERR_PTR(index);
 
        p = kmalloc(sizeof(*p), GFP_ATOMIC);
        if (p == NULL)
-               return p;
+               return ERR_PTR(-ENOMEM);
 
        memset(p, 0, sizeof(*p));
        p->br = br;
        p->dev = dev;
        p->path_cost = br_initial_port_cost(dev);
        p->priority = 0x80;
-
-       for (i=1;i<255;i++)
-               if (br_get_port(br, i) == NULL)
-                       break;
-
-       if (i == 255) {
-               kfree(p);
-               return NULL;
-       }
-
        dev->br_port = p;
-
-       p->port_no = i;
+       p->port_no = index;
        br_init_port(p);
        p->state = BR_STATE_DISABLED;
 
@@ -218,10 +233,10 @@
                return -ELOOP;
 
        dev_hold(dev);
-       if ((p = new_nbp(br, dev)) == NULL) {
-               spin_unlock_bh(&br->lock);
+       p = new_nbp(br, dev);
+       if (IS_ERR(p)) {
                dev_put(dev);
-               return -EXFULL;
+               return PTR_ERR(p);
        }
 
        dev_set_promiscuity(dev, 1);
diff -Nru a/net/bridge/br_private.h b/net/bridge/br_private.h
--- a/net/bridge/br_private.h   Thu Apr  1 12:55:31 2004
+++ b/net/bridge/br_private.h   Thu Apr  1 12:55:31 2004
@@ -57,7 +57,8 @@
        struct net_bridge               *br;
        struct net_device               *dev;
        struct list_head                list;
-       int                             port_no;
+       __u8                            port_no;
+       __u8                            priority;
 
        /* STP */
        port_id                         port_id;
@@ -69,7 +70,6 @@
        port_id                         designated_port;
        unsigned                        topology_change_ack:1;
        unsigned                        config_pending:1;
-       int                             priority;
 
        struct timer_list               forward_delay_timer;
        struct timer_list               hold_timer;