[BRIDGE]: netlink interface for link management

Add basic netlink support to the Ethernet bridge. Including:
 * dump interfaces in bridges
 * monitor link status changes
 * change state of bridge port

For some demo programs see:
	http://developer.osdl.org/shemminger/prototypes/brnl.tar.gz

These are to allow building a daemon that does alternative
implementations of Spanning Tree Protocol.

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

1 files changed, 199 insertions, 0 deletions

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
new file mode 100644
index 000000000000..881d7d1a732a
--- /dev/null
+++ b/net/bridge/br_netlink.c
@@ -0,0 +1,199 @@
+/*
+ *      Bridge netlink control interface
+ *
+ *      Authors:
+ *      Stephen Hemminger               <shemminger@osdl.org>
+ *
+ *      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/kernel.h>
+#include <linux/rtnetlink.h>
+#include "br_private.h"
+
+/*
+ * Create one netlink message for one interface
+ * Contains port and master info as well as carrier and bridge state.
+ */
+static int br_fill_ifinfo(struct sk_buff *skb, const struct net_bridge_port *port,
+                          u32 pid, u32 seq, int event, unsigned int flags)
+{
+        const struct net_bridge *br = port->br;
+        const struct net_device *dev = port->dev;
+        struct ifinfomsg *r;
+        struct nlmsghdr *nlh;
+        unsigned char *b = skb->tail;
+        u32 mtu = dev->mtu;
+        u8 operstate = netif_running(dev) ? dev->operstate : IF_OPER_DOWN;
+        u8 portstate = port->state;
+
+        pr_debug("br_fill_info event %d port %s master %s\n",
+                 event, dev->name, br->dev->name);
+
+        nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*r), flags);
+        r = NLMSG_DATA(nlh);
+        r->ifi_family = AF_BRIDGE;
+        r->__ifi_pad = 0;
+        r->ifi_type = dev->type;
+        r->ifi_index = dev->ifindex;
+        r->ifi_flags = dev_get_flags(dev);
+        r->ifi_change = 0;
+
+        RTA_PUT(skb, IFLA_IFNAME, strlen(dev->name)+1, dev->name);
+
+        RTA_PUT(skb, IFLA_MASTER, sizeof(int), &br->dev->ifindex);
+
+        if (dev->addr_len)
+                RTA_PUT(skb, IFLA_ADDRESS, dev->addr_len, dev->dev_addr);
+
+        RTA_PUT(skb, IFLA_MTU, sizeof(mtu), &mtu);
+        if (dev->ifindex != dev->iflink)
+                RTA_PUT(skb, IFLA_LINK, sizeof(int), &dev->iflink);
+
+
+        RTA_PUT(skb, IFLA_OPERSTATE, sizeof(operstate), &operstate);
+
+        if (event == RTM_NEWLINK)
+                RTA_PUT(skb, IFLA_PROTINFO, sizeof(portstate), &portstate);
+
+        nlh->nlmsg_len = skb->tail - b;
+
+        return skb->len;
+
+nlmsg_failure:
+rtattr_failure:
+
+        skb_trim(skb, b - skb->data);
+        return -EINVAL;
+}
+
+/*
+ * Notify listeners of a change in port information
+ */
+void br_ifinfo_notify(int event, struct net_bridge_port *port)
+{
+        struct sk_buff *skb;
+        int err = -ENOMEM;
+
+        pr_debug("bridge notify event=%d\n", event);
+        skb = alloc_skb(NLMSG_SPACE(sizeof(struct ifinfomsg) + 128),
+                        GFP_ATOMIC);
+        if (!skb)
+                goto err_out;
+
+        err = br_fill_ifinfo(skb, port, current->pid, 0, event, 0);
+        if (err)
+                goto err_kfree;
+
+        NETLINK_CB(skb).dst_group = RTNLGRP_LINK;
+        netlink_broadcast(rtnl, skb, 0, RTNLGRP_LINK, GFP_ATOMIC);
+        return;
+
+err_kfree:
+        kfree_skb(skb);
+err_out:
+        netlink_set_err(rtnl, 0, RTNLGRP_LINK, err);
+}
+
+/*
+ * Dump information about all ports, in response to GETLINK
+ */
+static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
+{
+        struct net_device *dev;
+        int idx;
+        int s_idx = cb->args[0];
+        int err = 0;
+
+        read_lock(&dev_base_lock);
+        for (dev = dev_base, idx = 0; dev; dev = dev->next) {
+                struct net_bridge_port *p = dev->br_port;
+
+                /* not a bridge port */
+                if (!p)
+                        continue;
+
+                if (idx < s_idx)
+                        continue;
+
+                err = br_fill_ifinfo(skb, p, NETLINK_CB(cb->skb).pid,
+                                     cb->nlh->nlmsg_seq, RTM_NEWLINK, NLM_F_MULTI);
+                if (err <= 0)
+                        break;
+                ++idx;
+        }
+        read_unlock(&dev_base_lock);
+
+        cb->args[0] = idx;
+
+        return skb->len;
+}
+
+/*
+ * Change state of port (ie from forwarding to blocking etc)
+ * Used by spanning tree in user space.
+ */
+static int br_rtm_setlink(struct sk_buff *skb,  struct nlmsghdr *nlh, void *arg)
+{
+        struct rtattr  **rta = arg;
+        struct ifinfomsg *ifm = NLMSG_DATA(nlh);
+        struct net_device *dev;
+        struct net_bridge_port *p;
+        u8 new_state;
+
+        if (ifm->ifi_family != AF_BRIDGE)
+                return -EPFNOSUPPORT;
+
+        /* Must pass valid state as PROTINFO */
+        if (rta[IFLA_PROTINFO-1]) {
+                u8 *pstate = RTA_DATA(rta[IFLA_PROTINFO-1]);
+                new_state = *pstate;
+        } else
+                return -EINVAL;
+
+        if (new_state > BR_STATE_BLOCKING)
+                return -EINVAL;
+
+        /* Find bridge port */
+        dev = __dev_get_by_index(ifm->ifi_index);
+        if (!dev)
+                return -ENODEV;
+
+        p = dev->br_port;
+        if (!p)
+                return -EINVAL;
+
+        /* if kernel STP is running, don't allow changes */
+        if (p->br->stp_enabled)
+                return -EBUSY;
+
+        if (!netif_running(dev))
+                return -ENETDOWN;
+
+        if (!netif_carrier_ok(dev) && new_state != BR_STATE_DISABLED)
+                return -ENETDOWN;
+
+        p->state = new_state;
+        br_log_state(p);
+        return 0;
+}
+
+
+static struct rtnetlink_link bridge_rtnetlink_table[RTM_NR_MSGTYPES] = {
+        [RTM_GETLINK - RTM_BASE] = { .dumpit    = br_dump_ifinfo, },
+        [RTM_SETLINK - RTM_BASE] = { .doit      = br_rtm_setlink, },
+};
+
+void __init br_netlink_init(void)
+{
+        rtnetlink_links[PF_BRIDGE] = bridge_rtnetlink_table;
+}
+
+void __exit br_netlink_fini(void)
+{
+        rtnetlink_links[PF_BRIDGE] = NULL;
+}
+