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   1 /*
   2  *      Handle incoming frames
   3  *      Linux ethernet bridge
   4  *
   5  *      Authors:
   6  *      Lennert Buytenhek               <buytenh@gnu.org>
   7  *
   8  *      $Id: br_input.c,v 1.10 2001/12/24 04:50:20 davem Exp $
   9  *
  10  *      This program is free software; you can redistribute it and/or
  11  *      modify it under the terms of the GNU General Public License
  12  *      as published by the Free Software Foundation; either version
  13  *      2 of the License, or (at your option) any later version.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/etherdevice.h>
  19 #include <linux/netfilter_bridge.h>
  20 #include "br_private.h"
  21
  22 /* Bridge group multicast address 802.1d (pg 51). */
  23 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  24
  25 static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
  26 {
  27         struct net_device *indev, *brdev = br->dev;
  28
  29         brdev->stats.rx_packets++;
  30         brdev->stats.rx_bytes += skb->len;
  31
  32         indev = skb->dev;
  33         skb->dev = brdev;
  34
  35         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  36                 netif_receive_skb);
  37 }
  38
  39 /* note: already called with rcu_read_lock (preempt_disabled) */
  40 int br_handle_frame_finish(struct sk_buff *skb)
  41 {
  42         const unsigned char *dest = eth_hdr(skb)->h_dest;
  43         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  44         struct net_bridge *br;
  45         struct net_bridge_fdb_entry *dst;
  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 (p->state == BR_STATE_LEARNING)
  56                 goto drop;
  57
  58         /* The packet skb2 goes to the local host (NULL to skip). */
  59         skb2 = NULL;
  60
  61         if (br->dev->flags & IFF_PROMISC)
  62                 skb2 = skb;
  63
  64         dst = NULL;
  65
  66         if (is_multicast_ether_addr(dest)) {
  67                 br->dev->stats.multicast++;
  68                 skb2 = skb;
  69         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  70                 skb2 = skb;
  71                 /* Do not forward the packet since it's local. */
  72                 skb = NULL;
  73         }
  74
  75         if (skb2 == skb)
  76                 skb2 = skb_clone(skb, GFP_ATOMIC);
  77
  78         if (skb2)
  79                 br_pass_frame_up(br, skb2);
  80
  81         if (skb) {
  82                 if (dst)
  83                         br_forward(dst->dst, skb);
  84                 else
  85                         br_flood_forward(br, skb);
  86         }
  87
  88 out:
  89         return 0;
  90 drop:
  91         kfree_skb(skb);
  92         goto out;
  93 }
  94
  95 /* note: already called with rcu_read_lock (preempt_disabled) */
  96 static int br_handle_local_finish(struct sk_buff *skb)
  97 {
  98         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  99
 100         if (p)
 101                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 102         return 0;        /* process further */
 103 }
 104
 105 /* Does address match the link local multicast address.
 106  * 01:80:c2:00:00:0X
 107  */
 108 static inline int is_link_local(const unsigned char *dest)
 109 {
 110         __be16 *a = (__be16 *)dest;
 111         static const __be16 *b = (const __be16 *)br_group_address;
 112         static const __be16 m = cpu_to_be16(0xfff0);
 113
 114         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 115 }
 116
 117 /*
 118  * Called via br_handle_frame_hook.
 119  * Return NULL if skb is handled
 120  * note: already called with rcu_read_lock (preempt_disabled)
 121  */
 122 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 123 {
 124         const unsigned char *dest = eth_hdr(skb)->h_dest;
 125         int (*rhook)(struct sk_buff *skb);
 126
 127         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 128                 goto drop;
 129
 130         skb = skb_share_check(skb, GFP_ATOMIC);
 131         if (!skb)
 132                 return NULL;
 133
 134         if (unlikely(is_link_local(dest))) {
 135                 /* Pause frames shouldn't be passed up by driver anyway */
 136                 if (skb->protocol == htons(ETH_P_PAUSE))
 137                         goto drop;
 138
 139                 /* Process STP BPDU's through normal netif_receive_skb() path */
 140                 if (p->br->stp_enabled != BR_NO_STP) {
 141                         if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 142                                     NULL, br_handle_local_finish))
 143                                 return NULL;
 144                         else
 145                                 return skb;
 146                 }
 147         }
 148
 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:
 166 drop:
 167                 kfree_skb(skb);
 168         }
 169         return NULL;
 170 }