root/net/bridge/br_stp_bpdu.c

DEFINITIONS

1. br_send_bpdu
2. br_set_ticks
3. br_get_ticks
4. br_send_config_bpdu
5. br_send_tcn_bpdu
6. br_stp_rcv

/*
 *      Spanning tree protocol; BPDU handling
 *      Linux ethernet bridge
 *
 *      Authors:
 *      Lennert Buytenhek               <buytenh@gnu.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/netfilter_bridge.h>
#include <linux/etherdevice.h>
#include <linux/llc.h>
#include <net/net_namespace.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#include <net/stp.h>
#include <asm/unaligned.h>

#include "br_private.h"
#include "br_private_stp.h"

#define STP_HZ          256

#define LLC_RESERVE sizeof(struct llc_pdu_un)

static void br_send_bpdu(struct net_bridge_port *p,
                         const unsigned char *data, int length)
{
        struct sk_buff *skb;

        skb = dev_alloc_skb(length+LLC_RESERVE);
        if (!skb)
                return;

        skb->dev = p->dev;
        skb->protocol = htons(ETH_P_802_2);

        skb_reserve(skb, LLC_RESERVE);
        memcpy(__skb_put(skb, length), data, length);

        llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
                            LLC_SAP_BSPAN, LLC_PDU_CMD);
        llc_pdu_init_as_ui_cmd(skb);

        llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);

        NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
                dev_queue_xmit);
}

static inline void br_set_ticks(unsigned char *dest, int j)
{
        unsigned long ticks = (STP_HZ * j)/ HZ;

        put_unaligned_be16(ticks, dest);
}

static inline int br_get_ticks(const unsigned char *src)
{
        unsigned long ticks = get_unaligned_be16(src);

        return DIV_ROUND_UP(ticks * HZ, STP_HZ);
}

/* called under bridge lock */
void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
{
        unsigned char buf[35];

        if (p->br->stp_enabled != BR_KERNEL_STP)
                return;

        buf[0] = 0;
        buf[1] = 0;
        buf[2] = 0;
        buf[3] = BPDU_TYPE_CONFIG;
        buf[4] = (bpdu->topology_change ? 0x01 : 0) |
                (bpdu->topology_change_ack ? 0x80 : 0);
        buf[5] = bpdu->root.prio[0];
        buf[6] = bpdu->root.prio[1];
        buf[7] = bpdu->root.addr[0];
        buf[8] = bpdu->root.addr[1];
        buf[9] = bpdu->root.addr[2];
        buf[10] = bpdu->root.addr[3];
        buf[11] = bpdu->root.addr[4];
        buf[12] = bpdu->root.addr[5];
        buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
        buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
        buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
        buf[16] = bpdu->root_path_cost & 0xFF;
        buf[17] = bpdu->bridge_id.prio[0];
        buf[18] = bpdu->bridge_id.prio[1];
        buf[19] = bpdu->bridge_id.addr[0];
        buf[20] = bpdu->bridge_id.addr[1];
        buf[21] = bpdu->bridge_id.addr[2];
        buf[22] = bpdu->bridge_id.addr[3];
        buf[23] = bpdu->bridge_id.addr[4];
        buf[24] = bpdu->bridge_id.addr[5];
        buf[25] = (bpdu->port_id >> 8) & 0xFF;
        buf[26] = bpdu->port_id & 0xFF;

        br_set_ticks(buf+27, bpdu->message_age);
        br_set_ticks(buf+29, bpdu->max_age);
        br_set_ticks(buf+31, bpdu->hello_time);
        br_set_ticks(buf+33, bpdu->forward_delay);

        br_send_bpdu(p, buf, 35);
}

/* called under bridge lock */
void br_send_tcn_bpdu(struct net_bridge_port *p)
{
        unsigned char buf[4];

        if (p->br->stp_enabled != BR_KERNEL_STP)
                return;

        buf[0] = 0;
        buf[1] = 0;
        buf[2] = 0;
        buf[3] = BPDU_TYPE_TCN;
        br_send_bpdu(p, buf, 4);
}

/*
 * Called from llc.
 *
 * NO locks, but rcu_read_lock (preempt_disabled)
 */
void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
                struct net_device *dev)
{
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        struct net_bridge_port *p = rcu_dereference(dev->br_port);
        struct net_bridge *br;
        const unsigned char *buf;

        if (!p)
                goto err;

        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;

        br = p->br;
        spin_lock(&br->lock);

        if (br->stp_enabled != BR_KERNEL_STP)
                goto out;

        if (!(br->dev->flags & IFF_UP))
                goto out;

        if (p->state == BR_STATE_DISABLED)
                goto out;

        if (compare_ether_addr(dest, br->group_addr) != 0)
                goto out;

        buf = skb_pull(skb, 3);

        if (buf[0] == BPDU_TYPE_CONFIG) {
                struct br_config_bpdu bpdu;

                if (!pskb_may_pull(skb, 32))
                        goto out;

                buf = skb->data;
                bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
                bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;

                bpdu.root.prio[0] = buf[2];
                bpdu.root.prio[1] = buf[3];
                bpdu.root.addr[0] = buf[4];
                bpdu.root.addr[1] = buf[5];
                bpdu.root.addr[2] = buf[6];
                bpdu.root.addr[3] = buf[7];
                bpdu.root.addr[4] = buf[8];
                bpdu.root.addr[5] = buf[9];
                bpdu.root_path_cost =
                        (buf[10] << 24) |
                        (buf[11] << 16) |
                        (buf[12] << 8) |
                        buf[13];
                bpdu.bridge_id.prio[0] = buf[14];
                bpdu.bridge_id.prio[1] = buf[15];
                bpdu.bridge_id.addr[0] = buf[16];
                bpdu.bridge_id.addr[1] = buf[17];
                bpdu.bridge_id.addr[2] = buf[18];
                bpdu.bridge_id.addr[3] = buf[19];
                bpdu.bridge_id.addr[4] = buf[20];
                bpdu.bridge_id.addr[5] = buf[21];
                bpdu.port_id = (buf[22] << 8) | buf[23];

                bpdu.message_age = br_get_ticks(buf+24);
                bpdu.max_age = br_get_ticks(buf+26);
                bpdu.hello_time = br_get_ticks(buf+28);
                bpdu.forward_delay = br_get_ticks(buf+30);

                br_received_config_bpdu(p, &bpdu);
        }

        else if (buf[0] == BPDU_TYPE_TCN) {
                br_received_tcn_bpdu(p);
        }
 out:
        spin_unlock(&br->lock);
 err:
        kfree_skb(skb);
}