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                 return;
  85
  86         if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
  87                 dev->stats.tx_dropped++;
  88                 return;
  89         }
  90         parp = arp_hdr(skb);
  91
  92         if (parp->ar_pro != htons(ETH_P_IP) ||
  93             parp->ar_op != htons(ARPOP_REQUEST) ||
  94             parp->ar_hln != dev->addr_len ||
  95             parp->ar_pln != 4)
  96                 return;
  97
  98         arpptr = (u8 *)parp + sizeof(struct arphdr);
  99         sha = arpptr;
 100         arpptr += dev->addr_len;        /* sha */
 101         memcpy(&sip, arpptr, sizeof(sip));
 102         arpptr += sizeof(sip);
 103         arpptr += dev->addr_len;        /* tha */
 104         memcpy(&tip, arpptr, sizeof(tip));
 105
 106         if (ipv4_is_loopback(tip) ||
 107             ipv4_is_multicast(tip))
 108                 return;
 109
 110         n = neigh_lookup(&arp_tbl, &tip, dev);
 111         if (n) {
 112                 struct net_bridge_fdb_entry *f;
 113
 114                 if (!(n->nud_state & NUD_VALID)) {
 115                         neigh_release(n);
 116                         return;
 117                 }
 118
 119                 f = __br_fdb_get(br, n->ha, vid);
 120                 if (f && ((p->flags & BR_PROXYARP) ||
 121                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
 122                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
 123                                  sha, n->ha, sha);
 124                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
 125                 }
 126
 127                 neigh_release(n);
 128         }
 129 }
 130
 131 /* note: already called with rcu_read_lock */
 132 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 133 {
 134         const unsigned char *dest = eth_hdr(skb)->h_dest;
 135         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 136         struct net_bridge *br;
 137         struct net_bridge_fdb_entry *dst;
 138         struct net_bridge_mdb_entry *mdst;
 139         struct sk_buff *skb2;
 140         bool unicast = true;
 141         u16 vid = 0;
 142
 143         if (!p || p->state == BR_STATE_DISABLED)
 144                 goto drop;
 145
 146         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
 147                 goto out;
 148
 149         /* insert into forwarding database after filtering to avoid spoofing */
 150         br = p->br;
 151         if (p->flags & BR_LEARNING)
 152                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 153
 154         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 155             br_multicast_rcv(br, p, skb, vid))
 156                 goto drop;
 157
 158         if (p->state == BR_STATE_LEARNING)
 159                 goto drop;
 160
 161         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 162
 163         /* The packet skb2 goes to the local host (NULL to skip). */
 164         skb2 = NULL;
 165
 166         if (br->dev->flags & IFF_PROMISC)
 167                 skb2 = skb;
 168
 169         dst = NULL;
 170
 171         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
 172                 br_do_proxy_arp(skb, br, vid, p);
 173
 174         if (is_broadcast_ether_addr(dest)) {
 175                 skb2 = skb;
 176                 unicast = false;
 177         } else if (is_multicast_ether_addr(dest)) {
 178                 mdst = br_mdb_get(br, skb, vid);
 179                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 180                     br_multicast_querier_exists(br, eth_hdr(skb))) {
 181                         if ((mdst && mdst->mglist) ||
 182                             br_multicast_is_router(br))
 183                                 skb2 = skb;
 184                         br_multicast_forward(mdst, skb, skb2);
 185                         skb = NULL;
 186                         if (!skb2)
 187                                 goto out;
 188                 } else
 189                         skb2 = skb;
 190
 191                 unicast = false;
 192                 br->dev->stats.multicast++;
 193         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
 194                         dst->is_local) {
 195                 skb2 = skb;
 196                 /* Do not forward the packet since it's local. */
 197                 skb = NULL;
 198         }
 199
 200         if (skb) {
 201                 if (dst) {
 202                         dst->used = jiffies;
 203                         br_forward(dst->dst, skb, skb2);
 204                 } else
 205                         br_flood_forward(br, skb, skb2, unicast);
 206         }
 207
 208         if (skb2)
 209                 return br_pass_frame_up(skb2);
 210
 211 out:
 212         return 0;
 213 drop:
 214         kfree_skb(skb);
 215         goto out;
 216 }
 217 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 218
 219 static void __br_handle_local_finish(struct sk_buff *skb)
 220 {
 221         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 222         u16 vid = 0;
 223
 224         /* check if vlan is allowed, to avoid spoofing */
 225         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 226                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 227 }
 228
 229 /* note: already called with rcu_read_lock */
 230 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 231 {
 232         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 233
 234         __br_handle_local_finish(skb);
 235
 236         BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
 237         br_pass_frame_up(skb);
 238         return 0;
 239 }
 240
 241 /*
 242  * Return NULL if skb is handled
 243  * note: already called with rcu_read_lock
 244  */
 245 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 246 {
 247         struct net_bridge_port *p;
 248         struct sk_buff *skb = *pskb;
 249         const unsigned char *dest = eth_hdr(skb)->h_dest;
 250         br_should_route_hook_t *rhook;
 251
 252         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 253                 return RX_HANDLER_PASS;
 254
 255         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 256                 goto drop;
 257
 258         skb = skb_share_check(skb, GFP_ATOMIC);
 259         if (!skb)
 260                 return RX_HANDLER_CONSUMED;
 261
 262         p = br_port_get_rcu(skb->dev);
 263
 264         if (unlikely(is_link_local_ether_addr(dest))) {
 265                 u16 fwd_mask = p->br->group_fwd_mask_required;
 266
 267                 /*
 268                  * See IEEE 802.1D Table 7-10 Reserved addresses
 269                  *
 270                  * Assignment                           Value
 271                  * Bridge Group Address         01-80-C2-00-00-00
 272                  * (MAC Control) 802.3          01-80-C2-00-00-01
 273                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 274                  * 802.1X PAE address           01-80-C2-00-00-03
 275                  *
 276                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 277                  *
 278                  * Others reserved for future standardization
 279                  */
 280                 switch (dest[5]) {
 281                 case 0x00:      /* Bridge Group Address */
 282                         /* If STP is turned off,
 283                            then must forward to keep loop detection */
 284                         if (p->br->stp_enabled == BR_NO_STP ||
 285                             fwd_mask & (1u << dest[5]))
 286                                 goto forward;
 287                         *pskb = skb;
 288                         __br_handle_local_finish(skb);
 289                         return RX_HANDLER_PASS;
 290
 291                 case 0x01:      /* IEEE MAC (Pause) */
 292                         goto drop;
 293
 294                 default:
 295                         /* Allow selective forwarding for most other protocols */
 296                         fwd_mask |= p->br->group_fwd_mask;
 297                         if (fwd_mask & (1u << dest[5]))
 298                                 goto forward;
 299                 }
 300
 301                 /* Deliver packet to local host only */
 302                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
 303                         NULL, skb, skb->dev, NULL, br_handle_local_finish);
 304                 return RX_HANDLER_CONSUMED;
 305         }
 306
 307 forward:
 308         switch (p->state) {
 309         case BR_STATE_FORWARDING:
 310                 rhook = rcu_dereference(br_should_route_hook);
 311                 if (rhook) {
 312                         if ((*rhook)(skb)) {
 313                                 *pskb = skb;
 314                                 return RX_HANDLER_PASS;
 315                         }
 316                         dest = eth_hdr(skb)->h_dest;
 317                 }
 318                 /* fall through */
 319         case BR_STATE_LEARNING:
 320                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 321                         skb->pkt_type = PACKET_HOST;
 322
 323                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
 324                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 325                         br_handle_frame_finish);
 326                 break;
 327         default:
 328 drop:
 329                 kfree_skb(skb);
 330         }
 331         return RX_HANDLER_CONSUMED;
 332 }