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/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). */
  21 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  22
  23 static int br_pass_frame_up(struct sk_buff *skb)
  24 {
  25         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  26
  27         brdev->stats.rx_packets++;
  28         brdev->stats.rx_bytes += skb->len;
  29
  30         indev = skb->dev;
  31         skb->dev = brdev;
  32
  33         return 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) */
  38 int 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         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  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 (skb) {
  79                 if (dst)
  80                         br_forward(dst->dst, skb);
  81                 else
  82                         br_flood_forward(br, skb);
  83         }
  84
  85         if (skb2)
  86                 return br_pass_frame_up(skb2);
  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                 /* If STP is turned off, then forward */
 140                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 141                         goto forward;
 142
 143                 if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 144                             NULL, br_handle_local_finish))
 145                         return NULL;    /* frame consumed by filter */
 146                 else
 147                         return skb;     /* continue processing */
 148         }
 149
 150 forward:
 151         switch (p->state) {
 152         case BR_STATE_FORWARDING:
 153                 rhook = rcu_dereference(br_should_route_hook);
 154                 if (rhook != NULL) {
 155                         if (rhook(skb))
 156                                 return skb;
 157                         dest = eth_hdr(skb)->h_dest;
 158                 }
 159                 /* fall through */
 160         case BR_STATE_LEARNING:
 161                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 162                         skb->pkt_type = PACKET_HOST;
 163
 164                 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 165                         br_handle_frame_finish);
 166                 break;
 167         default:
 168 drop:
 169                 kfree_skb(skb);
 170         }
 171         return NULL;
 172 }