br_stp_bpdu.c

Go to the documentation of this file.

/*
 *  Spanning tree protocol; BPDU handling
 *  Linux ethernet bridge
 *
 *  Authors:
 *  Lennert Buytenhek       <[email protected]>
 *
 *  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 <linux/slab.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);

    skb_reset_mac_header(skb);

    NF_HOOK(NFPROTO_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
 */
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;
    struct net_bridge *br;
    const unsigned char *buf;

    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;

    p = br_port_get_rcu(dev);
    if (!p)
        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 (!ether_addr_equal(dest, br->group_addr))
        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);

        if (bpdu.message_age > bpdu.max_age) {
            if (net_ratelimit())
                br_notice(p->br,
                      "port %u config from %pM"
                      " (message_age %ul > max_age %ul)\n",
                      p->port_no,
                      eth_hdr(skb)->h_source,
                      bpdu.message_age, bpdu.max_age);
            goto out;
        }

        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);
}