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