/*
 *      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/slab.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/netfilter_bridge.h>
#include <linux/export.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 };

/* Hook for brouter */
br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
EXPORT_SYMBOL(br_should_route_hook);

static int br_pass_frame_up(struct sk_buff *skb)
{
        struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
        struct net_bridge *br = netdev_priv(brdev);
        struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);

        u64_stats_update_begin(&brstats->syncp);
        brstats->rx_packets++;
        brstats->rx_bytes += skb->len;
        u64_stats_update_end(&brstats->syncp);

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

        return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
                       netif_receive_skb);
}

/* note: already called with rcu_read_lock */
int br_handle_frame_finish(struct sk_buff *skb)
{
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        struct net_bridge_port *p = br_port_get_rcu(skb->dev);
        struct net_bridge *br;
        struct net_bridge_fdb_entry *dst;
        struct net_bridge_mdb_entry *mdst;
        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 (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
            br_multicast_rcv(br, p, skb))
                goto drop;

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

        BR_INPUT_SKB_CB(skb)->brdev = br->dev;

        /* 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_broadcast_ether_addr(dest))
                skb2 = skb;
        else if (is_multicast_ether_addr(dest)) {
                mdst = br_mdb_get(br, skb);
                if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
                        if ((mdst && mdst->mglist) ||
                            br_multicast_is_router(br))
                                skb2 = skb;
                        br_multicast_forward(mdst, skb, skb2);
                        skb = NULL;
                        if (!skb2)
                                goto out;
                } else
                        skb2 = skb;

                br->dev->stats.multicast++;
        } 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 (skb) {
                if (dst) {
                        dst->used = jiffies;
                        br_forward(dst->dst, skb, skb2);
                } else
                        br_flood_forward(br, skb, skb2);
        }

        if (skb2)
                return br_pass_frame_up(skb2);

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

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

        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;
}

/*
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock
 */
rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
{
        struct net_bridge_port *p;
        struct sk_buff *skb = *pskb;
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        br_should_route_hook_t *rhook;

        if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
                return RX_HANDLER_PASS;

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

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

        p = br_port_get_rcu(skb->dev);

        if (unlikely(is_link_local(dest))) {
                /*
                 * See IEEE 802.1D Table 7-10 Reserved addresses
                 *
                 * Assignment                           Value
                 * Bridge Group Address         01-80-C2-00-00-00
                 * (MAC Control) 802.3          01-80-C2-00-00-01
                 * (Link Aggregation) 802.3     01-80-C2-00-00-02
                 * 802.1X PAE address           01-80-C2-00-00-03
                 *
                 * 802.1AB LLDP                 01-80-C2-00-00-0E
                 *
                 * Others reserved for future standardization
                 */
                switch (dest[5]) {
                case 0x00:      /* Bridge Group Address */
                        /* If STP is turned off,
                           then must forward to keep loop detection */
                        if (p->br->stp_enabled == BR_NO_STP)
                                goto forward;
                        break;

                case 0x01:      /* IEEE MAC (Pause) */
                        goto drop;

                default:
                        /* Allow selective forwarding for most other protocols */
                        if (p->br->group_fwd_mask & (1u << dest[5]))
                                goto forward;
                }

                /* Deliver packet to local host only */
                if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
                            NULL, br_handle_local_finish)) {
                        return RX_HANDLER_CONSUMED; /* consumed by filter */
                } else {
                        *pskb = skb;
                        return RX_HANDLER_PASS; /* continue processing */
                }
        }

forward:
        switch (p->state) {
        case BR_STATE_FORWARDING:
                rhook = rcu_dereference(br_should_route_hook);
                if (rhook) {
                        if ((*rhook)(skb)) {
                                *pskb = skb;
                                return RX_HANDLER_PASS;
                        }
                        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(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
                        br_handle_frame_finish);
                break;
        default:
drop:
                kfree_skb(skb);
        }
        return RX_HANDLER_CONSUMED;
}