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 /* Hook for brouter */
  25 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  26 EXPORT_SYMBOL(br_should_route_hook);
  27
  28 static int br_pass_frame_up(struct sk_buff *skb)
  29 {
  30         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  31         struct net_bridge *br = netdev_priv(brdev);
  32         struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
  33
  34         u64_stats_update_begin(&brstats->syncp);
  35         brstats->rx_packets++;
  36         brstats->rx_bytes += skb->len;
  37         u64_stats_update_end(&brstats->syncp);
  38
  39         indev = skb->dev;
  40         skb->dev = brdev;
  41
  42         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  43                        netif_receive_skb);
  44 }
  45
  46 /* note: already called with rcu_read_lock */
  47 int br_handle_frame_finish(struct sk_buff *skb)
  48 {
  49         const unsigned char *dest = eth_hdr(skb)->h_dest;
  50         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
  51         struct net_bridge *br;
  52         struct net_bridge_fdb_entry *dst;
  53         struct net_bridge_mdb_entry *mdst;
  54         struct sk_buff *skb2;
  55
  56         if (!p || p->state == BR_STATE_DISABLED)
  57                 goto drop;
  58
  59         /* insert into forwarding database after filtering to avoid spoofing */
  60         br = p->br;
  61         br_fdb_update(br, p, eth_hdr(skb)->h_source);
  62
  63         if (is_multicast_ether_addr(dest) &&
  64             br_multicast_rcv(br, p, skb))
  65                 goto drop;
  66
  67         if (p->state == BR_STATE_LEARNING)
  68                 goto drop;
  69
  70         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
  71
  72         /* The packet skb2 goes to the local host (NULL to skip). */
  73         skb2 = NULL;
  74
  75         if (br->dev->flags & IFF_PROMISC)
  76                 skb2 = skb;
  77
  78         dst = NULL;
  79
  80         if (is_multicast_ether_addr(dest)) {
  81                 mdst = br_mdb_get(br, skb);
  82                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
  83                         if ((mdst && mdst->mglist) ||
  84                             br_multicast_is_router(br))
  85                                 skb2 = skb;
  86                         br_multicast_forward(mdst, skb, skb2);
  87                         skb = NULL;
  88                         if (!skb2)
  89                                 goto out;
  90                 } else
  91                         skb2 = skb;
  92
  93                 br->dev->stats.multicast++;
  94         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
  95                 skb2 = skb;
  96                 /* Do not forward the packet since it's local. */
  97                 skb = NULL;
  98         }
  99
 100         if (skb) {
 101                 if (dst)
 102                         br_forward(dst->dst, skb, skb2);
 103                 else
 104                         br_flood_forward(br, skb, skb2);
 105         }
 106
 107         if (skb2)
 108                 return br_pass_frame_up(skb2);
 109
 110 out:
 111         return 0;
 112 drop:
 113         kfree_skb(skb);
 114         goto out;
 115 }
 116
 117 /* note: already called with rcu_read_lock */
 118 static int br_handle_local_finish(struct sk_buff *skb)
 119 {
 120         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 121
 122         br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
 123         return 0;        /* process further */
 124 }
 125
 126 /* Does address match the link local multicast address.
 127  * 01:80:c2:00:00:0X
 128  */
 129 static inline int is_link_local(const unsigned char *dest)
 130 {
 131         __be16 *a = (__be16 *)dest;
 132         static const __be16 *b = (const __be16 *)br_group_address;
 133         static const __be16 m = cpu_to_be16(0xfff0);
 134
 135         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 136 }
 137
 138 /*
 139  * Return NULL if skb is handled
 140  * note: already called with rcu_read_lock
 141  */
 142 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 143 {
 144         struct net_bridge_port *p;
 145         struct sk_buff *skb = *pskb;
 146         const unsigned char *dest = eth_hdr(skb)->h_dest;
 147         br_should_route_hook_t *rhook;
 148
 149         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 150                 return RX_HANDLER_PASS;
 151
 152         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 153                 goto drop;
 154
 155         skb = skb_share_check(skb, GFP_ATOMIC);
 156         if (!skb)
 157                 return RX_HANDLER_CONSUMED;
 158
 159         p = br_port_get_rcu(skb->dev);
 160
 161         if (unlikely(is_link_local(dest))) {
 162                 /* Pause frames shouldn't be passed up by driver anyway */
 163                 if (skb->protocol == htons(ETH_P_PAUSE))
 164                         goto drop;
 165
 166                 /* If STP is turned off, then forward */
 167                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
 168                         goto forward;
 169
 170                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 171                             NULL, br_handle_local_finish)) {
 172                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 173                 } else {
 174                         *pskb = skb;
 175                         return RX_HANDLER_PASS; /* continue processing */
 176                 }
 177         }
 178
 179 forward:
 180         switch (p->state) {
 181         case BR_STATE_FORWARDING:
 182                 rhook = rcu_dereference(br_should_route_hook);
 183                 if (rhook) {
 184                         if ((*rhook)(skb)) {
 185                                 *pskb = skb;
 186                                 return RX_HANDLER_PASS;
 187                         }
 188                         dest = eth_hdr(skb)->h_dest;
 189                 }
 190                 /* fall through */
 191         case BR_STATE_LEARNING:
 192                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
 193                         skb->pkt_type = PACKET_HOST;
 194
 195                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 196                         br_handle_frame_finish);
 197                 break;
 198         default:
 199 drop:
 200                 kfree_skb(skb);
 201         }
 202         return RX_HANDLER_CONSUMED;
 203 }