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         br_drop_fake_rtable(skb);
  33         return netif_receive_skb(skb);
  34 }
  35
  36 static int br_pass_frame_up(struct sk_buff *skb)
  37 {
  38         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
  39         struct net_bridge *br = netdev_priv(brdev);
  40         struct net_bridge_vlan_group *vg;
  41         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
  42
  43         u64_stats_update_begin(&brstats->syncp);
  44         brstats->rx_packets++;
  45         brstats->rx_bytes += skb->len;
  46         u64_stats_update_end(&brstats->syncp);
  47
  48         vg = br_vlan_group_rcu(br);
  49         /* Bridge is just like any other port.  Make sure the
  50          * packet is allowed except in promisc modue when someone
  51          * may be running packet capture.
  52          */
  53         if (!(brdev->flags & IFF_PROMISC) &&
  54             !br_allowed_egress(vg, skb)) {
  55                 kfree_skb(skb);
  56                 return NET_RX_DROP;
  57         }
  58
  59         indev = skb->dev;
  60         skb->dev = brdev;
  61         skb = br_handle_vlan(br, vg, skb);
  62         if (!skb)
  63                 return NET_RX_DROP;
  64
  65         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
  66                        dev_net(indev), NULL, skb, indev, NULL,
  67                        br_netif_receive_skb);
  68 }
  69
  70 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
  71                             u16 vid, struct net_bridge_port *p)
  72 {
  73         struct net_device *dev = br->dev;
  74         struct neighbour *n;
  75         struct arphdr *parp;
  76         u8 *arpptr, *sha;
  77         __be32 sip, tip;
  78
  79         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
  80
  81         if ((dev->flags & IFF_NOARP) ||
  82             !pskb_may_pull(skb, arp_hdr_len(dev)))
  83                 return;
  84
  85         parp = arp_hdr(skb);
  86
  87         if (parp->ar_pro != htons(ETH_P_IP) ||
  88             parp->ar_op != htons(ARPOP_REQUEST) ||
  89             parp->ar_hln != dev->addr_len ||
  90             parp->ar_pln != 4)
  91                 return;
  92
  93         arpptr = (u8 *)parp + sizeof(struct arphdr);
  94         sha = arpptr;
  95         arpptr += dev->addr_len;        /* sha */
  96         memcpy(&sip, arpptr, sizeof(sip));
  97         arpptr += sizeof(sip);
  98         arpptr += dev->addr_len;        /* tha */
  99         memcpy(&tip, arpptr, sizeof(tip));
 100
 101         if (ipv4_is_loopback(tip) ||
 102             ipv4_is_multicast(tip))
 103                 return;
 104
 105         n = neigh_lookup(&arp_tbl, &tip, dev);
 106         if (n) {
 107                 struct net_bridge_fdb_entry *f;
 108
 109                 if (!(n->nud_state & NUD_VALID)) {
 110                         neigh_release(n);
 111                         return;
 112                 }
 113
 114                 f = __br_fdb_get(br, n->ha, vid);
 115                 if (f && ((p->flags & BR_PROXYARP) ||
 116                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
 117                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
 118                                  sha, n->ha, sha);
 119                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
 120                 }
 121
 122                 neigh_release(n);
 123         }
 124 }
 125
 126 /* note: already called with rcu_read_lock */
 127 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 128 {
 129         const unsigned char *dest = eth_hdr(skb)->h_dest;
 130         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 131         struct net_bridge *br;
 132         struct net_bridge_fdb_entry *dst;
 133         struct net_bridge_mdb_entry *mdst;
 134         struct sk_buff *skb2;
 135         bool unicast = true;
 136         u16 vid = 0;
 137
 138         if (!p || p->state == BR_STATE_DISABLED)
 139                 goto drop;
 140
 141         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
 142                 goto out;
 143
 144         /* insert into forwarding database after filtering to avoid spoofing */
 145         br = p->br;
 146         if (p->flags & BR_LEARNING)
 147                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 148
 149         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 150             br_multicast_rcv(br, p, skb, vid))
 151                 goto drop;
 152
 153         if (p->state == BR_STATE_LEARNING)
 154                 goto drop;
 155
 156         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
 157
 158         /* The packet skb2 goes to the local host (NULL to skip). */
 159         skb2 = NULL;
 160
 161         if (br->dev->flags & IFF_PROMISC)
 162                 skb2 = skb;
 163
 164         dst = NULL;
 165
 166         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
 167                 br_do_proxy_arp(skb, br, vid, p);
 168
 169         if (is_broadcast_ether_addr(dest)) {
 170                 skb2 = skb;
 171                 unicast = false;
 172         } else if (is_multicast_ether_addr(dest)) {
 173                 mdst = br_mdb_get(br, skb, vid);
 174                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
 175                     br_multicast_querier_exists(br, eth_hdr(skb))) {
 176                         if ((mdst && mdst->mglist) ||
 177                             br_multicast_is_router(br))
 178                                 skb2 = skb;
 179                         br_multicast_forward(mdst, skb, skb2);
 180                         skb = NULL;
 181                         if (!skb2)
 182                                 goto out;
 183                 } else
 184                         skb2 = skb;
 185
 186                 unicast = false;
 187                 br->dev->stats.multicast++;
 188         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
 189                         dst->is_local) {
 190                 skb2 = skb;
 191                 /* Do not forward the packet since it's local. */
 192                 skb = NULL;
 193         }
 194
 195         if (skb) {
 196                 if (dst) {
 197                         dst->used = jiffies;
 198                         br_forward(dst->dst, skb, skb2);
 199                 } else
 200                         br_flood_forward(br, skb, skb2, unicast);
 201         }
 202
 203         if (skb2)
 204                 return br_pass_frame_up(skb2);
 205
 206 out:
 207         return 0;
 208 drop:
 209         kfree_skb(skb);
 210         goto out;
 211 }
 212 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 213
 214 /* note: already called with rcu_read_lock */
 215 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 216 {
 217         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 218         u16 vid = 0;
 219
 220         /* check if vlan is allowed, to avoid spoofing */
 221         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 222                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
 223         return 0;        /* process further */
 224 }
 225
 226 /*
 227  * Return NULL if skb is handled
 228  * note: already called with rcu_read_lock
 229  */
 230 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 231 {
 232         struct net_bridge_port *p;
 233         struct sk_buff *skb = *pskb;
 234         const unsigned char *dest = eth_hdr(skb)->h_dest;
 235         br_should_route_hook_t *rhook;
 236
 237         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
 238                 return RX_HANDLER_PASS;
 239
 240         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 241                 goto drop;
 242
 243         skb = skb_share_check(skb, GFP_ATOMIC);
 244         if (!skb)
 245                 return RX_HANDLER_CONSUMED;
 246
 247         p = br_port_get_rcu(skb->dev);
 248
 249         if (unlikely(is_link_local_ether_addr(dest))) {
 250                 u16 fwd_mask = p->br->group_fwd_mask_required;
 251
 252                 /*
 253                  * See IEEE 802.1D Table 7-10 Reserved addresses
 254                  *
 255                  * Assignment                           Value
 256                  * Bridge Group Address         01-80-C2-00-00-00
 257                  * (MAC Control) 802.3          01-80-C2-00-00-01
 258                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
 259                  * 802.1X PAE address           01-80-C2-00-00-03
 260                  *
 261                  * 802.1AB LLDP                 01-80-C2-00-00-0E
 262                  *
 263                  * Others reserved for future standardization
 264                  */
 265                 switch (dest[5]) {
 266                 case 0x00:      /* Bridge Group Address */
 267                         /* If STP is turned off,
 268                            then must forward to keep loop detection */
 269                         if (p->br->stp_enabled == BR_NO_STP ||
 270                             fwd_mask & (1u << dest[5]))
 271                                 goto forward;
 272                         break;
 273
 274                 case 0x01:      /* IEEE MAC (Pause) */
 275                         goto drop;
 276
 277                 default:
 278                         /* Allow selective forwarding for most other protocols */
 279                         fwd_mask |= p->br->group_fwd_mask;
 280                         if (fwd_mask & (1u << dest[5]))
 281                                 goto forward;
 282                 }
 283
 284                 /* Deliver packet to local host only */
 285                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
 286                             dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 287                             br_handle_local_finish)) {
 288                         return RX_HANDLER_CONSUMED; /* consumed by filter */
 289                 } else {
 290                         *pskb = skb;
 291                         return RX_HANDLER_PASS; /* continue processing */
 292                 }
 293         }
 294
 295 forward:
 296         switch (p->state) {
 297         case BR_STATE_FORWARDING:
 298                 rhook = rcu_dereference(br_should_route_hook);
 299                 if (rhook) {
 300                         if ((*rhook)(skb)) {
 301                                 *pskb = skb;
 302                                 return RX_HANDLER_PASS;
 303                         }
 304                         dest = eth_hdr(skb)->h_dest;
 305                 }
 306                 /* fall through */
 307         case BR_STATE_LEARNING:
 308                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
 309                         skb->pkt_type = PACKET_HOST;
 310
 311                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
 312                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
 313                         br_handle_frame_finish);
 314                 break;
 315         default:
 316 drop:
 317                 kfree_skb(skb);
 318         }
 319         return RX_HANDLER_CONSUMED;
 320 }