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   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
  28         brdev->stats.rx_packets++;
  29         brdev->stats.rx_bytes += skb->len;
  30
  31         indev = skb->dev;
  32         skb->dev = brdev;
  33
  34         return NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  35                        netif_receive_skb);
  36 }
  37
  38 /* note: already called with rcu_read_lock (preempt_disabled) */
  39 int br_handle_frame_finish(struct sk_buff *skb)
  40 {
  41         const unsigned char *dest = eth_hdr(skb)->h_dest;
  42         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  43         struct net_bridge *br;
  44         struct net_bridge_fdb_entry *dst;
  45         struct net_bridge_mdb_entry *mdst;
  46         struct sk_buff *skb2;
  47
  48         if (!p || p->state == BR_STATE_DISABLED)
  49                 goto drop;
  50
  51         /* insert into forwarding database after filtering to avoid spoofing */
  52         br = p->br;
  53         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  54
  55         if (is_multicast_ether_addr(dest) &&
  56             br_multicast_rcv(br, p, skb))
  57                 goto drop;
  58
  59         if (p->state == BR_STATE_LEARNING)
  60                 goto drop;
  61
  62         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  63
  64         /* The packet skb2 goes to the local host (NULL to skip). */
  65         skb2 = NULL;
  66
  67         if (br->dev->flags & IFF_PROMISC)
  68                 skb2 = skb;
  69
  70         dst = NULL;
  71
  72         if (is_multicast_ether_addr(dest)) {
  73                 mdst = br_mdb_get(br, skb);
  74                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  75                         if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
  76                             br_multicast_is_router(br))
  77                                 skb2 = skb;
  78                         br_multicast_forward(mdst, skb, skb2);
  79                         skb = NULL;
  80                         if (!skb2)
  81                                 goto out;
  82                 } else
  83                         skb2 = skb;
  84
  85                 br->dev->stats.multicast++;
  86         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  87                 skb2 = skb;
  88                 /* Do not forward the packet since it's local. */
  89                 skb = NULL;
  90         }
  91
  92         if (skb) {
  93                 if (dst)
  94                         br_forward(dst->dst, skb, skb2);
  95                 else
  96                         br_flood_forward(br, skb, skb2);
  97         }
  98
  99         if (skb2)
 100                 return br_pass_frame_up(skb2);
 101
 102 out:
 103         return 0;
 104 drop:
 105         kfree_skb(skb);
 106         goto out;
 107 }
 108
 109 /* note: already called with rcu_read_lock (preempt_disabled) */
 110 static int br_handle_local_finish(struct sk_buff *skb)
 111 {
 112         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
 113
 114         if (p)
 115                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 116         return 0;        /* process further */
 117 }
 118
 119 /* Does address match the link local multicast address.
 120  * 01:80:c2:00:00:0X
 121  */
 122 static inline int is_link_local(const unsigned char *dest)
 123 {
 124         __be16 *a = (__be16 *)dest;
 125         static const __be16 *b = (const __be16 *)br_group_address;
 126         static const __be16 m = cpu_to_be16(0xfff0);
 127
 128         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 129 }
 130
 131 /*
 132  * Called via br_handle_frame_hook.
 133  * Return NULL if skb is handled
 134  * note: already called with rcu_read_lock (preempt_disabled)
 135  */
 136 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 137 {
 138         const unsigned char *dest = eth_hdr(skb)->h_dest;
 139         int (*rhook)(struct sk_buff *skb);
 140
 141         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 142                 goto drop;
 143
 144         skb = skb_share_check(skb, GFP_ATOMIC);
 145         if (!skb)
 146                 return NULL;
 147
 148         if (unlikely(is_link_local(dest))) {
 149                 /* Pause frames shouldn't be passed up by driver anyway */
 150                 if (skb->protocol == htons(ETH_P_PAUSE))
 151                         goto drop;
 152
 153                 /* If STP is turned off, then forward */
 154                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 155                         goto forward;
 156
 157                 if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 158                             NULL, br_handle_local_finish))
 159                         return NULL;    /* frame consumed by filter */
 160                 else
 161                         return skb;     /* continue processing */
 162         }
 163
 164 forward:
 165         switch (p->state) {
 166         case BR_STATE_FORWARDING:
 167                 rhook = rcu_dereference(br_should_route_hook);
 168                 if (rhook != NULL) {
 169                         if (rhook(skb))
 170                                 return skb;
 171                         dest = eth_hdr(skb)->h_dest;
 172                 }
 173                 /* fall through */
 174         case BR_STATE_LEARNING:
 175                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 176                         skb->pkt_type = PACKET_HOST;
 177
 178                 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 179                         br_handle_frame_finish);
 180                 break;
 181         default:
 182 drop:
 183                 kfree_skb(skb);
 184         }
 185         return NULL;
 186 }