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 <linux/neighbour.h>
  20 #include <net/arp.h>
  21 #include <linux/export.h>
  22 #include <linux/rculist.h>
  23 #include "br_private.h"
  24
  25 /* Hook for brouter */
  26 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  27 EXPORT_SYMBOL(br_should_route_hook);
  28
  29 static int br_pass_frame_up(struct sk_buff *skb)
  30 {
  31         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  32         struct net_bridge *br = netdev_priv(brdev);
  33         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
  34         struct net_port_vlans *pv;
  35
  36         u64_stats_update_begin(&brstats->syncp);
  37         brstats->rx_packets++;
  38         brstats->rx_bytes += skb->len;
  39         u64_stats_update_end(&brstats->syncp);
  40
  41         /* Bridge is just like any other port.  Make sure the
  42          * packet is allowed except in promisc modue when someone
  43          * may be running packet capture.
  44          */
  45         pv = br_get_vlan_info(br);
  46         if (!(brdev->flags & IFF_PROMISC) &&
  47             !br_allowed_egress(br, pv, skb)) {
  48                 kfree_skb(skb);
  49                 return NET_RX_DROP;
  50         }
  51
  52         indev = skb->dev;
  53         skb->dev = brdev;
  54         skb = br_handle_vlan(br, pv, skb);
  55         if (!skb)
  56                 return NET_RX_DROP;
  57
  58         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  59                        netif_receive_skb);
  60 }
  61
  62 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
  63                             u16 vid, struct net_bridge_port *p)
  64 {
  65         struct net_device *dev = br->dev;
  66         struct neighbour *n;
  67         struct arphdr *parp;
  68         u8 *arpptr, *sha;
  69         __be32 sip, tip;
  70
  71         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
  72
  73         if (dev->flags & IFF_NOARP)
  74                 return;
  75
  76         if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
  77                 dev->stats.tx_dropped++;
  78                 return;
  79         }
  80         parp = arp_hdr(skb);
  81
  82         if (parp->ar_pro != htons(ETH_P_IP) ||
  83             parp->ar_op != htons(ARPOP_REQUEST) ||
  84             parp->ar_hln != dev->addr_len ||
  85             parp->ar_pln != 4)
  86                 return;
  87
  88         arpptr = (u8 *)parp + sizeof(struct arphdr);
  89         sha = arpptr;
  90         arpptr += dev->addr_len;        /* sha */
  91         memcpy(&sip, arpptr, sizeof(sip));
  92         arpptr += sizeof(sip);
  93         arpptr += dev->addr_len;        /* tha */
  94         memcpy(&tip, arpptr, sizeof(tip));
  95
  96         if (ipv4_is_loopback(tip) ||
  97             ipv4_is_multicast(tip))
  98                 return;
  99
 100         n = neigh_lookup(&arp_tbl, &tip, dev);
 101         if (n) {
 102                 struct net_bridge_fdb_entry *f;
 103
 104                 if (!(n->nud_state & NUD_VALID)) {
 105                         neigh_release(n);
 106                         return;
 107                 }
 108
 109                 f = __br_fdb_get(br, n->ha, vid);
 110                 if (f && ((p->flags & BR_PROXYARP) ||
 111                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
 112                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
 113                                  sha, n->ha, sha);
 114                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
 115                 }
 116
 117                 neigh_release(n);
 118         }
 119 }
 120
 121 /* note: already called with rcu_read_lock */
 122 int br_handle_frame_finish(struct sk_buff *skb)
 123 {
 124         const unsigned char *dest = eth_hdr(skb)->h_dest;
 125         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 126         struct net_bridge *br;
 127         struct net_bridge_fdb_entry *dst;
 128         struct net_bridge_mdb_entry *mdst;
 129         struct sk_buff *skb2;
 130         bool unicast = true;
 131         u16 vid = 0;
 132
 133         if (!p || p->state == BR_STATE_DISABLED)
 134                 goto drop;
 135
 136         if (!br_allowed_ingress(p->br, nbp_get_vlan_info(p), skb, &vid))
 137                 goto out;
 138
 139         /* insert into forwarding database after filtering to avoid spoofing */
 140         br = p->br;
 141         if (p->flags & BR_LEARNING)
 142                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 143
 144         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 145             br_multicast_rcv(br, p, skb, vid))
 146                 goto drop;
 147
 148         if (p->state == BR_STATE_LEARNING)
 149                 goto drop;
 150
 151         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 152
 153         /* The packet skb2 goes to the local host (NULL to skip). */
 154         skb2 = NULL;
 155
 156         if (br->dev->flags & IFF_PROMISC)
 157                 skb2 = skb;
 158
 159         dst = NULL;
 160
 161         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
 162                 br_do_proxy_arp(skb, br, vid, p);
 163
 164         if (is_broadcast_ether_addr(dest)) {
 165                 skb2 = skb;
 166                 unicast = false;
 167         } else if (is_multicast_ether_addr(dest)) {
 168                 mdst = br_mdb_get(br, skb, vid);
 169                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 170                     br_multicast_querier_exists(br, eth_hdr(skb))) {
 171                         if ((mdst && mdst->mglist) ||
 172                             br_multicast_is_router(br))
 173                                 skb2 = skb;
 174                         br_multicast_forward(mdst, skb, skb2);
 175                         skb = NULL;
 176                         if (!skb2)
 177                                 goto out;
 178                 } else
 179                         skb2 = skb;
 180
 181                 unicast = false;
 182                 br->dev->stats.multicast++;
 183         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
 184                         dst->is_local) {
 185                 skb2 = skb;
 186                 /* Do not forward the packet since it's local. */
 187                 skb = NULL;
 188         }
 189
 190         if (skb) {
 191                 if (dst) {
 192                         dst->used = jiffies;
 193                         br_forward(dst->dst, skb, skb2);
 194                 } else
 195                         br_flood_forward(br, skb, skb2, unicast);
 196         }
 197
 198         if (skb2)
 199                 return br_pass_frame_up(skb2);
 200
 201 out:
 202         return 0;
 203 drop:
 204         kfree_skb(skb);
 205         goto out;
 206 }
 207 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 208
 209 /* note: already called with rcu_read_lock */
 210 static int br_handle_local_finish(struct sk_buff *skb)
 211 {
 212         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 213         u16 vid = 0;
 214
 215         /* check if vlan is allowed, to avoid spoofing */
 216         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 217                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 218         return 0;        /* process further */
 219 }
 220
 221 /*
 222  * Return NULL if skb is handled
 223  * note: already called with rcu_read_lock
 224  */
 225 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 226 {
 227         struct net_bridge_port *p;
 228         struct sk_buff *skb = *pskb;
 229         const unsigned char *dest = eth_hdr(skb)->h_dest;
 230         br_should_route_hook_t *rhook;
 231
 232         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 233                 return RX_HANDLER_PASS;
 234
 235         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 236                 goto drop;
 237
 238         skb = skb_share_check(skb, GFP_ATOMIC);
 239         if (!skb)
 240                 return RX_HANDLER_CONSUMED;
 241
 242         p = br_port_get_rcu(skb->dev);
 243
 244         if (unlikely(is_link_local_ether_addr(dest))) {
 245                 u16 fwd_mask = p->br->group_fwd_mask_required;
 246
 247                 /*
 248                  * See IEEE 802.1D Table 7-10 Reserved addresses
 249                  *
 250                  * Assignment                           Value
 251                  * Bridge Group Address         01-80-C2-00-00-00
 252                  * (MAC Control) 802.3          01-80-C2-00-00-01
 253                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 254                  * 802.1X PAE address           01-80-C2-00-00-03
 255                  *
 256                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 257                  *
 258                  * Others reserved for future standardization
 259                  */
 260                 switch (dest[5]) {
 261                 case 0x00:      /* Bridge Group Address */
 262                         /* If STP is turned off,
 263                            then must forward to keep loop detection */
 264                         if (p->br->stp_enabled == BR_NO_STP ||
 265                             fwd_mask & (1u << dest[5]))
 266                                 goto forward;
 267                         break;
 268
 269                 case 0x01:      /* IEEE MAC (Pause) */
 270                         goto drop;
 271
 272                 default:
 273                         /* Allow selective forwarding for most other protocols */
 274                         fwd_mask |= p->br->group_fwd_mask;
 275                         if (fwd_mask & (1u << dest[5]))
 276                                 goto forward;
 277                 }
 278
 279                 /* Deliver packet to local host only */
 280                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
 281                             NULL, br_handle_local_finish)) {
 282                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 283                 } else {
 284                         *pskb = skb;
 285                         return RX_HANDLER_PASS; /* continue processing */
 286                 }
 287         }
 288
 289 forward:
 290         switch (p->state) {
 291         case BR_STATE_FORWARDING:
 292                 rhook = rcu_dereference(br_should_route_hook);
 293                 if (rhook) {
 294                         if ((*rhook)(skb)) {
 295                                 *pskb = skb;
 296                                 return RX_HANDLER_PASS;
 297                         }
 298                         dest = eth_hdr(skb)->h_dest;
 299                 }
 300                 /* fall through */
 301         case BR_STATE_LEARNING:
 302                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 303                         skb->pkt_type = PACKET_HOST;
 304
 305                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 306                         br_handle_frame_finish);
 307                 break;
 308         default:
 309 drop:
 310                 kfree_skb(skb);
 311         }
 312         return RX_HANDLER_CONSUMED;
 313 }