LXR linux/net/bridge/br

   1/*
   2 *      Handle incoming frames
   3 *      Linux ethernet bridge
   4 *
   5 *      Authors:
   6 *      Lennert Buytenhek               <buytenh@gnu.org>
   7 *
   8 *      This program is free software; you can redistribute it and/or
   9 *      modify it under the terms of the GNU General Public License
  10 *      as published by the Free Software Foundation; either version
  11 *      2 of the License, or (at your option) any later version.
  12 */
  13
  14#include <linux/kernel.h>
  15#include <linux/netdevice.h>
  16#include <linux/etherdevice.h>
  17#include <linux/netfilter_bridge.h>
  18#include "br_private.h"
  19
  20/* Bridge group multicast address 802.1d (pg 51). */
  21const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  22
  23static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
  24{
  25        struct net_device *indev, *brdev = br->dev;
  26
  27        brdev->stats.rx_packets++;
  28        brdev->stats.rx_bytes += skb->len;
  29
  30        indev = skb->dev;
  31        skb->dev = brdev;
  32
  33        NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  34                netif_receive_skb);
  35}
  36
  37/* note: already called with rcu_read_lock (preempt_disabled) */
  38int br_handle_frame_finish(struct sk_buff *skb)
  39{
  40        const unsigned char *dest = eth_hdr(skb)->h_dest;
  41        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  42        struct net_bridge *br;
  43        struct net_bridge_fdb_entry *dst;
  44        struct sk_buff *skb2;
  45
  46        if (!p || p->state == BR_STATE_DISABLED)
  47                goto drop;
  48
  49        /* insert into forwarding database after filtering to avoid spoofing */
  50        br = p->br;
  51        br_fdb_update(br, p, eth_hdr(skb)->h_source);
  52
  53        if (p->state == BR_STATE_LEARNING)
  54                goto drop;
  55
  56        /* The packet skb2 goes to the local host (NULL to skip). */
  57        skb2 = NULL;
  58
  59        if (br->dev->flags & IFF_PROMISC)
  60                skb2 = skb;
  61
  62        dst = NULL;
  63
  64        if (is_multicast_ether_addr(dest)) {
  65                br->dev->stats.multicast++;
  66                skb2 = skb;
  67        } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  68                skb2 = skb;
  69                /* Do not forward the packet since it's local. */
  70                skb = NULL;
  71        }
  72
  73        if (skb2 == skb)
  74                skb2 = skb_clone(skb, GFP_ATOMIC);
  75
  76        if (skb2)
  77                br_pass_frame_up(br, skb2);
  78
  79        if (skb) {
  80                if (dst)
  81                        br_forward(dst->dst, skb);
  82                else
  83                        br_flood_forward(br, skb);
  84        }
  85
  86out:
  87        return 0;
  88drop:
  89        kfree_skb(skb);
  90        goto out;
  91}
  92
  93/* note: already called with rcu_read_lock (preempt_disabled) */
  94static int br_handle_local_finish(struct sk_buff *skb)
  95{
  96        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  97
  98        if (p)
  99                br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 100        return 0;        /* process further */
 101}
 102
 103/* Does address match the link local multicast address.
 104 * 01:80:c2:00:00:0X
 105 */
 106static inline int is_link_local(const unsigned char *dest)
 107{
 108        __be16 *a = (__be16 *)dest;
 109        static const __be16 *b = (const __be16 *)br_group_address;
 110        static const __be16 m = cpu_to_be16(0xfff0);
 111
 112        return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 113}
 114
 115/*
 116 * Called via br_handle_frame_hook.
 117 * Return NULL if skb is handled
 118 * note: already called with rcu_read_lock (preempt_disabled)
 119 */
 120struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 121{
 122        const unsigned char *dest = eth_hdr(skb)->h_dest;
 123        int (*rhook)(struct sk_buff *skb);
 124
 125        if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 126                goto drop;
 127
 128        skb = skb_share_check(skb, GFP_ATOMIC);
 129        if (!skb)
 130                return NULL;
 131
 132        if (unlikely(is_link_local(dest))) {
 133                /* Pause frames shouldn't be passed up by driver anyway */
 134                if (skb->protocol == htons(ETH_P_PAUSE))
 135                        goto drop;
 136
 137                /* If STP is turned off, then forward */
 138                if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 139                        goto forward;
 140
 141                if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 142                            NULL, br_handle_local_finish))
 143                        return NULL;    /* frame consumed by filter */
 144                else
 145                        return skb;     /* continue processing */
 146        }
 147
 148forward:
 149        switch (p->state) {
 150        case BR_STATE_FORWARDING:
 151                rhook = rcu_dereference(br_should_route_hook);
 152                if (rhook != NULL) {
 153                        if (rhook(skb))
 154                                return skb;
 155                        dest = eth_hdr(skb)->h_dest;
 156                }
 157                /* fall through */
 158        case BR_STATE_LEARNING:
 159                if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 160                        skb->pkt_type = PACKET_HOST;
 161
 162                NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 163                        br_handle_frame_finish);
 164                break;
 165        default:
 166drop:
 167                kfree_skb(skb);
 168        }
 169        return NULL;
 170}
 171