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
  30 br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
  31 {
  32         return netif_receive_skb(skb);
  33 }
  34
  35 static int br_pass_frame_up(struct sk_buff *skb)
  36 {
  37         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  38         struct net_bridge *br = netdev_priv(brdev);
  39         struct net_bridge_vlan_group *vg;
  40         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
  41
  42         u64_stats_update_begin(&brstats->syncp);
  43         brstats->rx_packets++;
  44         brstats->rx_bytes += skb->len;
  45         u64_stats_update_end(&brstats->syncp);
  46
  47         vg = br_vlan_group_rcu(br);
  48         /* Bridge is just like any other port.  Make sure the
  49          * packet is allowed except in promisc modue when someone
  50          * may be running packet capture.
  51          */
  52         if (!(brdev->flags & IFF_PROMISC) &&
  53             !br_allowed_egress(vg, skb)) {
  54                 kfree_skb(skb);
  55                 return NET_RX_DROP;
  56         }
  57
  58         indev = skb->dev;
  59         skb->dev = brdev;
  60         skb = br_handle_vlan(br, vg, skb);
  61         if (!skb)
  62                 return NET_RX_DROP;
  63         /* update the multicast stats if the packet is IGMP/MLD */
  64         br_multicast_count(br, NULL, skb, br_multicast_igmp_type(skb),
  65                            BR_MCAST_DIR_TX);
  66
  67         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
  68                        dev_net(indev), NULL, skb, indev, NULL,
  69                        br_netif_receive_skb);
  70 }
  71
  72 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
  73                             u16 vid, struct net_bridge_port *p)
  74 {
  75         struct net_device *dev = br->dev;
  76         struct neighbour *n;
  77         struct arphdr *parp;
  78         u8 *arpptr, *sha;
  79         __be32 sip, tip;
  80
  81         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
  82
  83         if ((dev->flags & IFF_NOARP) ||
  84             !pskb_may_pull(skb, arp_hdr_len(dev)))
  85                 return;
  86
  87         parp = arp_hdr(skb);
  88
  89         if (parp->ar_pro != htons(ETH_P_IP) ||
  90             parp->ar_op != htons(ARPOP_REQUEST) ||
  91             parp->ar_hln != dev->addr_len ||
  92             parp->ar_pln != 4)
  93                 return;
  94
  95         arpptr = (u8 *)parp + sizeof(struct arphdr);
  96         sha = arpptr;
  97         arpptr += dev->addr_len;        /* sha */
  98         memcpy(&sip, arpptr, sizeof(sip));
  99         arpptr += sizeof(sip);
 100         arpptr += dev->addr_len;        /* tha */
 101         memcpy(&tip, arpptr, sizeof(tip));
 102
 103         if (ipv4_is_loopback(tip) ||
 104             ipv4_is_multicast(tip))
 105                 return;
 106
 107         n = neigh_lookup(&arp_tbl, &tip, dev);
 108         if (n) {
 109                 struct net_bridge_fdb_entry *f;
 110
 111                 if (!(n->nud_state & NUD_VALID)) {
 112                         neigh_release(n);
 113                         return;
 114                 }
 115
 116                 f = __br_fdb_get(br, n->ha, vid);
 117                 if (f && ((p->flags & BR_PROXYARP) ||
 118                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
 119                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
 120                                  sha, n->ha, sha);
 121                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
 122                 }
 123
 124                 neigh_release(n);
 125         }
 126 }
 127
 128 /* note: already called with rcu_read_lock */
 129 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 130 {
 131         bool local_rcv = false, mcast_hit = false, unicast = true;
 132         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 133         const unsigned char *dest = eth_hdr(skb)->h_dest;
 134         struct net_bridge_fdb_entry *dst = NULL;
 135         struct net_bridge_mdb_entry *mdst;
 136         struct net_bridge *br;
 137         u16 vid = 0;
 138
 139         if (!p || p->state == BR_STATE_DISABLED)
 140                 goto drop;
 141
 142         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
 143                 goto out;
 144
 145         /* insert into forwarding database after filtering to avoid spoofing */
 146         br = p->br;
 147         if (p->flags & BR_LEARNING)
 148                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 149
 150         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 151             br_multicast_rcv(br, p, skb, vid))
 152                 goto drop;
 153
 154         if (p->state == BR_STATE_LEARNING)
 155                 goto drop;
 156
 157         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 158
 159         local_rcv = !!(br->dev->flags & IFF_PROMISC);
 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                 local_rcv = true;
 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                                 local_rcv = true;
 174                                 br->dev->stats.multicast++;
 175                         }
 176                         mcast_hit = true;
 177                 } else {
 178                         local_rcv = true;
 179                         br->dev->stats.multicast++;
 180                 }
 181                 unicast = false;
 182         } else if ((dst = __br_fdb_get(br, dest, vid)) && dst->is_local) {
 183                 /* Do not forward the packet since it's local. */
 184                 return br_pass_frame_up(skb);
 185         }
 186
 187         if (dst) {
 188                 dst->used = jiffies;
 189                 br_forward(dst->dst, skb, local_rcv, false);
 190         } else {
 191                 if (!mcast_hit)
 192                         br_flood(br, skb, unicast, local_rcv, false);
 193                 else
 194                         br_multicast_flood(mdst, skb, local_rcv, false);
 195         }
 196
 197         if (local_rcv)
 198                 return br_pass_frame_up(skb);
 199
 200 out:
 201         return 0;
 202 drop:
 203         kfree_skb(skb);
 204         goto out;
 205 }
 206 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 207
 208 static void __br_handle_local_finish(struct sk_buff *skb)
 209 {
 210         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 211         u16 vid = 0;
 212
 213         /* check if vlan is allowed, to avoid spoofing */
 214         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 215                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 216 }
 217
 218 /* note: already called with rcu_read_lock */
 219 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 220 {
 221         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 222
 223         __br_handle_local_finish(skb);
 224
 225         BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
 226         br_pass_frame_up(skb);
 227         return 0;
 228 }
 229
 230 /*
 231  * Return NULL if skb is handled
 232  * note: already called with rcu_read_lock
 233  */
 234 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 235 {
 236         struct net_bridge_port *p;
 237         struct sk_buff *skb = *pskb;
 238         const unsigned char *dest = eth_hdr(skb)->h_dest;
 239         br_should_route_hook_t *rhook;
 240
 241         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 242                 return RX_HANDLER_PASS;
 243
 244         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 245                 goto drop;
 246
 247         skb = skb_share_check(skb, GFP_ATOMIC);
 248         if (!skb)
 249                 return RX_HANDLER_CONSUMED;
 250
 251         p = br_port_get_rcu(skb->dev);
 252
 253         if (unlikely(is_link_local_ether_addr(dest))) {
 254                 u16 fwd_mask = p->br->group_fwd_mask_required;
 255
 256                 /*
 257                  * See IEEE 802.1D Table 7-10 Reserved addresses
 258                  *
 259                  * Assignment                           Value
 260                  * Bridge Group Address         01-80-C2-00-00-00
 261                  * (MAC Control) 802.3          01-80-C2-00-00-01
 262                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 263                  * 802.1X PAE address           01-80-C2-00-00-03
 264                  *
 265                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 266                  *
 267                  * Others reserved for future standardization
 268                  */
 269                 switch (dest[5]) {
 270                 case 0x00:      /* Bridge Group Address */
 271                         /* If STP is turned off,
 272                            then must forward to keep loop detection */
 273                         if (p->br->stp_enabled == BR_NO_STP ||
 274                             fwd_mask & (1u << dest[5]))
 275                                 goto forward;
 276                         *pskb = skb;
 277                         __br_handle_local_finish(skb);
 278                         return RX_HANDLER_PASS;
 279
 280                 case 0x01:      /* IEEE MAC (Pause) */
 281                         goto drop;
 282
 283                 case 0x0E:      /* 802.1AB LLDP */
 284                         fwd_mask |= p->br->group_fwd_mask;
 285                         if (fwd_mask & (1u << dest[5]))
 286                                 goto forward;
 287                         *pskb = skb;
 288                         __br_handle_local_finish(skb);
 289                         return RX_HANDLER_PASS;
 290
 291                 default:
 292                         /* Allow selective forwarding for most other protocols */
 293                         fwd_mask |= p->br->group_fwd_mask;
 294                         if (fwd_mask & (1u << dest[5]))
 295                                 goto forward;
 296                 }
 297
 298                 /* Deliver packet to local host only */
 299                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
 300                         NULL, skb, skb->dev, NULL, br_handle_local_finish);
 301                 return RX_HANDLER_CONSUMED;
 302         }
 303
 304 forward:
 305         switch (p->state) {
 306         case BR_STATE_FORWARDING:
 307                 rhook = rcu_dereference(br_should_route_hook);
 308                 if (rhook) {
 309                         if ((*rhook)(skb)) {
 310                                 *pskb = skb;
 311                                 return RX_HANDLER_PASS;
 312                         }
 313                         dest = eth_hdr(skb)->h_dest;
 314                 }
 315                 /* fall through */
 316         case BR_STATE_LEARNING:
 317                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 318                         skb->pkt_type = PACKET_HOST;
 319
 320                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
 321                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 322                         br_handle_frame_finish);
 323                 break;
 324         default:
 325 drop:
 326                 kfree_skb(skb);
 327         }
 328         return RX_HANDLER_CONSUMED;
 329 }