net/bridge/br_input.c

   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/slab.h>
  15 #include <linux/kernel.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/etherdevice.h>
  18 #include <linux/netfilter_bridge.h>
  19 #include "br_private.h"
  20
  21 /* Bridge group multicast address 802.1d (pg 51). */
  22 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  23
  24 static int br_pass_frame_up(struct sk_buff *skb)
  25 {
  26         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  27         struct net_bridge *br = netdev_priv(brdev);
  28         struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
  29
  30         u64_stats_update_begin(&brstats->syncp);
  31         brstats->rx_packets++;
  32         brstats->rx_bytes += skb->len;
  33         u64_stats_update_end(&brstats->syncp);
  34
  35         indev = skb->dev;
  36         skb->dev = brdev;
  37
  38         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  39                        netif_receive_skb);
  40 }
  41
  42 /* note: already called with rcu_read_lock */
  43 int br_handle_frame_finish(struct sk_buff *skb)
  44 {
  45         const unsigned char *dest = eth_hdr(skb)->h_dest;
  46         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
  47         struct net_bridge *br;
  48         struct net_bridge_fdb_entry *dst;
  49         struct net_bridge_mdb_entry *mdst;
  50         struct sk_buff *skb2;
  51
  52         if (!p || p->state == BR_STATE_DISABLED)
  53                 goto drop;
  54
  55         /* insert into forwarding database after filtering to avoid spoofing */
  56         br = p->br;
  57         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  58
  59         if (is_multicast_ether_addr(dest) &&
  60             br_multicast_rcv(br, p, skb))
  61                 goto drop;
  62
  63         if (p->state == BR_STATE_LEARNING)
  64                 goto drop;
  65
  66         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  67
  68         /* The packet skb2 goes to the local host (NULL to skip). */
  69         skb2 = NULL;
  70
  71         if (br->dev->flags & IFF_PROMISC)
  72                 skb2 = skb;
  73
  74         dst = NULL;
  75
  76         if (is_multicast_ether_addr(dest)) {
  77                 mdst = br_mdb_get(br, skb);
  78                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  79                         if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
  80                             br_multicast_is_router(br))
  81                                 skb2 = skb;
  82                         br_multicast_forward(mdst, skb, skb2);
  83                         skb = NULL;
  84                         if (!skb2)
  85                                 goto out;
  86                 } else
  87                         skb2 = skb;
  88
  89                 br->dev->stats.multicast++;
  90         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  91                 skb2 = skb;
  92                 /* Do not forward the packet since it's local. */
  93                 skb = NULL;
  94         }
  95
  96         if (skb) {
  97                 if (dst)
  98                         br_forward(dst->dst, skb, skb2);
  99                 else
 100                         br_flood_forward(br, skb, skb2);
 101         }
 102
 103         if (skb2)
 104                 return br_pass_frame_up(skb2);
 105
 106 out:
 107         return 0;
 108 drop:
 109         kfree_skb(skb);
 110         goto out;
 111 }
 112
 113 /* note: already called with rcu_read_lock */
 114 static int br_handle_local_finish(struct sk_buff *skb)
 115 {
 116         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 117
 118         br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 119         return 0;        /* process further */
 120 }
 121
 122 /* Does address match the link local multicast address.
 123  * 01:80:c2:00:00:0X
 124  */
 125 static inline int is_link_local(const unsigned char *dest)
 126 {
 127         __be16 *a = (__be16 *)dest;
 128         static const __be16 *b = (const __be16 *)br_group_address;
 129         static const __be16 m = cpu_to_be16(0xfff0);
 130
 131         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 132 }
 133
 134 /*
 135  * Return NULL if skb is handled
 136  * note: already called with rcu_read_lock
 137  */
 138 struct sk_buff *br_handle_frame(struct sk_buff *skb)
 139 {
 140         struct net_bridge_port *p;
 141         const unsigned char *dest = eth_hdr(skb)->h_dest;
 142         int (*rhook)(struct sk_buff *skb);
 143
 144         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 145                 return skb;
 146
 147         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 148                 goto drop;
 149
 150         skb = skb_share_check(skb, GFP_ATOMIC);
 151         if (!skb)
 152                 return NULL;
 153
 154         p = br_port_get_rcu(skb->dev);
 155
 156         if (unlikely(is_link_local(dest))) {
 157                 /* Pause frames shouldn't be passed up by driver anyway */
 158                 if (skb->protocol == htons(ETH_P_PAUSE))
 159                         goto drop;
 160
 161                 /* If STP is turned off, then forward */
 162                 if (p->br->stp_enabled == BR_NO_STP)
 163                         goto forward;
 164
 165                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 166                             NULL, br_handle_local_finish))
 167                         return NULL;    /* frame consumed by filter */
 168                 else
 169                         return skb;     /* continue processing */
 170         }
 171
 172 forward:
 173         switch (p->state) {
 174         case BR_STATE_FORWARDING:
 175                 rhook = rcu_dereference(br_should_route_hook);
 176                 if (rhook != NULL) {
 177                         if (rhook(skb))
 178                                 return skb;
 179                         dest = eth_hdr(skb)->h_dest;
 180                 }
 181                 /* fall through */
 182         case BR_STATE_LEARNING:
 183                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 184                         skb->pkt_type = PACKET_HOST;
 185
 186                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 187                         br_handle_frame_finish);
 188                 break;
 189         default:
 190 drop:
 191                 kfree_skb(skb);
 192         }
 193         return NULL;
 194 }