root/net/bridge/br_input.c

DEFINITIONS

1. br_pass_frame_up
2. br_handle_frame_finish
3. br_handle_local_finish
4. is_link_local
5. br_handle_frame

/*
 *      Handle incoming frames
 *      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/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/netfilter_bridge.h>
#include "br_private.h"

/* Bridge group multicast address 802.1d (pg 51). */
const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };

static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
{
        struct net_device *indev, *brdev = br->dev;

        brdev->stats.rx_packets++;
        brdev->stats.rx_bytes += skb->len;

        indev = skb->dev;
        skb->dev = brdev;

        NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
                netif_receive_skb);
}

/* note: already called with rcu_read_lock (preempt_disabled) */
int br_handle_frame_finish(struct sk_buff *skb)
{
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
        struct net_bridge *br;
        struct net_bridge_fdb_entry *dst;
        struct sk_buff *skb2;

        if (!p || p->state == BR_STATE_DISABLED)
                goto drop;

        /* insert into forwarding database after filtering to avoid spoofing */
        br = p->br;
        br_fdb_update(br, p, eth_hdr(skb)->h_source);

        if (p->state == BR_STATE_LEARNING)
                goto drop;

        /* The packet skb2 goes to the local host (NULL to skip). */
        skb2 = NULL;

        if (br->dev->flags & IFF_PROMISC)
                skb2 = skb;

        dst = NULL;

        if (is_multicast_ether_addr(dest)) {
                br->dev->stats.multicast++;
                skb2 = skb;
        } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
                skb2 = skb;
                /* Do not forward the packet since it's local. */
                skb = NULL;
        }

        if (skb2 == skb)
                skb2 = skb_clone(skb, GFP_ATOMIC);

        if (skb2)
                br_pass_frame_up(br, skb2);

        if (skb) {
                if (dst)
                        br_forward(dst->dst, skb);
                else
                        br_flood_forward(br, skb);
        }

out:
        return 0;
drop:
        kfree_skb(skb);
        goto out;
}

/* note: already called with rcu_read_lock (preempt_disabled) */
static int br_handle_local_finish(struct sk_buff *skb)
{
        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);

        if (p)
                br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
        return 0;        /* process further */
}

/* Does address match the link local multicast address.
 * 01:80:c2:00:00:0X
 */
static inline int is_link_local(const unsigned char *dest)
{
        __be16 *a = (__be16 *)dest;
        static const __be16 *b = (const __be16 *)br_group_address;
        static const __be16 m = cpu_to_be16(0xfff0);

        return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
}

/*
 * Called via br_handle_frame_hook.
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock (preempt_disabled)
 */
struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
{
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        int (*rhook)(struct sk_buff *skb);

        if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
                goto drop;

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
                return NULL;

        if (unlikely(is_link_local(dest))) {
                /* Pause frames shouldn't be passed up by driver anyway */
                if (skb->protocol == htons(ETH_P_PAUSE))
                        goto drop;

                if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
                            NULL, br_handle_local_finish))
                        return NULL;    /* frame consumed by filter */
                else
                        return skb;     /* continue processing */
        }

        switch (p->state) {
        case BR_STATE_FORWARDING:
                rhook = rcu_dereference(br_should_route_hook);
                if (rhook != NULL) {
                        if (rhook(skb))
                                return skb;
                        dest = eth_hdr(skb)->h_dest;
                }
                /* fall through */
        case BR_STATE_LEARNING:
                if (!compare_ether_addr(p->br->dev->dev_addr, dest))
                        skb->pkt_type = PACKET_HOST;

                NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
                        br_handle_frame_finish);
                break;
        default:
drop:
                kfree_skb(skb);
        }
        return NULL;
}