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 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
  62static 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 */
 117int 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
 198out:
 199        return 0;
 200drop:
 201        kfree_skb(skb);
 202        goto out;
 203}
 204EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 205
 206/* note: already called with rcu_read_lock */
 207static 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 */
 222rx_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
 286forward:
 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:
 306drop:
 307                kfree_skb(skb);
 308        }
 309        return RX_HANDLER_CONSUMED;
 310}
 311