LXR linux/net/bridge/br

   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 */
  26br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
  27EXPORT_SYMBOL(br_should_route_hook);
  28
  29static int
  30br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
  31{
  32        return netif_receive_skb(skb);
  33}
  34
  35static 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
  72static 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 */
 129int 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
 200out:
 201        return 0;
 202drop:
 203        kfree_skb(skb);
 204        goto out;
 205}
 206EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 207
 208static 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 */
 219static 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 */
 234rx_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
 304forward:
 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:
 325drop:
 326                kfree_skb(skb);
 327        }
 328        return RX_HANDLER_CONSUMED;
 329}
 330