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