linux/net/bridge/br_forward.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *      Forwarding decision
   4 *      Linux ethernet bridge
   5 *
   6 *      Authors:
   7 *      Lennert Buytenhek               <buytenh@gnu.org>
   8 */
   9
  10#include <linux/err.h>
  11#include <linux/slab.h>
  12#include <linux/kernel.h>
  13#include <linux/netdevice.h>
  14#include <linux/netpoll.h>
  15#include <linux/skbuff.h>
  16#include <linux/if_vlan.h>
  17#include <linux/netfilter_bridge.h>
  18#include "br_private.h"
  19
  20/* Don't forward packets to originating port or forwarding disabled */
  21static inline int should_deliver(const struct net_bridge_port *p,
  22                                 const struct sk_buff *skb)
  23{
  24        struct net_bridge_vlan_group *vg;
  25
  26        vg = nbp_vlan_group_rcu(p);
  27        return ((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
  28                p->state == BR_STATE_FORWARDING && br_allowed_egress(vg, skb) &&
  29                nbp_switchdev_allowed_egress(p, skb) &&
  30                !br_skb_isolated(p, skb);
  31}
  32
  33int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
  34{
  35        skb_push(skb, ETH_HLEN);
  36        if (!is_skb_forwardable(skb->dev, skb))
  37                goto drop;
  38
  39        br_drop_fake_rtable(skb);
  40
  41        if (skb->ip_summed == CHECKSUM_PARTIAL &&
  42            eth_type_vlan(skb->protocol)) {
  43                int depth;
  44
  45                if (!__vlan_get_protocol(skb, skb->protocol, &depth))
  46                        goto drop;
  47
  48                skb_set_network_header(skb, depth);
  49        }
  50
  51        dev_queue_xmit(skb);
  52
  53        return 0;
  54
  55drop:
  56        kfree_skb(skb);
  57        return 0;
  58}
  59EXPORT_SYMBOL_GPL(br_dev_queue_push_xmit);
  60
  61int br_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  62{
  63        skb->tstamp = 0;
  64        return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING,
  65                       net, sk, skb, NULL, skb->dev,
  66                       br_dev_queue_push_xmit);
  67
  68}
  69EXPORT_SYMBOL_GPL(br_forward_finish);
  70
  71static void __br_forward(const struct net_bridge_port *to,
  72                         struct sk_buff *skb, bool local_orig)
  73{
  74        struct net_bridge_vlan_group *vg;
  75        struct net_device *indev;
  76        struct net *net;
  77        int br_hook;
  78
  79        vg = nbp_vlan_group_rcu(to);
  80        skb = br_handle_vlan(to->br, to, vg, skb);
  81        if (!skb)
  82                return;
  83
  84        indev = skb->dev;
  85        skb->dev = to->dev;
  86        if (!local_orig) {
  87                if (skb_warn_if_lro(skb)) {
  88                        kfree_skb(skb);
  89                        return;
  90                }
  91                br_hook = NF_BR_FORWARD;
  92                skb_forward_csum(skb);
  93                net = dev_net(indev);
  94        } else {
  95                if (unlikely(netpoll_tx_running(to->br->dev))) {
  96                        skb_push(skb, ETH_HLEN);
  97                        if (!is_skb_forwardable(skb->dev, skb))
  98                                kfree_skb(skb);
  99                        else
 100                                br_netpoll_send_skb(to, skb);
 101                        return;
 102                }
 103                br_hook = NF_BR_LOCAL_OUT;
 104                net = dev_net(skb->dev);
 105                indev = NULL;
 106        }
 107
 108        NF_HOOK(NFPROTO_BRIDGE, br_hook,
 109                net, NULL, skb, indev, skb->dev,
 110                br_forward_finish);
 111}
 112
 113static int deliver_clone(const struct net_bridge_port *prev,
 114                         struct sk_buff *skb, bool local_orig)
 115{
 116        struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 117
 118        skb = skb_clone(skb, GFP_ATOMIC);
 119        if (!skb) {
 120                dev->stats.tx_dropped++;
 121                return -ENOMEM;
 122        }
 123
 124        __br_forward(prev, skb, local_orig);
 125        return 0;
 126}
 127
 128/**
 129 * br_forward - forward a packet to a specific port
 130 * @to: destination port
 131 * @skb: packet being forwarded
 132 * @local_rcv: packet will be received locally after forwarding
 133 * @local_orig: packet is locally originated
 134 *
 135 * Should be called with rcu_read_lock.
 136 */
 137void br_forward(const struct net_bridge_port *to,
 138                struct sk_buff *skb, bool local_rcv, bool local_orig)
 139{
 140        if (unlikely(!to))
 141                goto out;
 142
 143        /* redirect to backup link if the destination port is down */
 144        if (rcu_access_pointer(to->backup_port) && !netif_carrier_ok(to->dev)) {
 145                struct net_bridge_port *backup_port;
 146
 147                backup_port = rcu_dereference(to->backup_port);
 148                if (unlikely(!backup_port))
 149                        goto out;
 150                to = backup_port;
 151        }
 152
 153        if (should_deliver(to, skb)) {
 154                if (local_rcv)
 155                        deliver_clone(to, skb, local_orig);
 156                else
 157                        __br_forward(to, skb, local_orig);
 158                return;
 159        }
 160
 161out:
 162        if (!local_rcv)
 163                kfree_skb(skb);
 164}
 165EXPORT_SYMBOL_GPL(br_forward);
 166
 167static struct net_bridge_port *maybe_deliver(
 168        struct net_bridge_port *prev, struct net_bridge_port *p,
 169        struct sk_buff *skb, bool local_orig)
 170{
 171        u8 igmp_type = br_multicast_igmp_type(skb);
 172        int err;
 173
 174        if (!should_deliver(p, skb))
 175                return prev;
 176
 177        if (!prev)
 178                goto out;
 179
 180        err = deliver_clone(prev, skb, local_orig);
 181        if (err)
 182                return ERR_PTR(err);
 183out:
 184        br_multicast_count(p->br, p, skb, igmp_type, BR_MCAST_DIR_TX);
 185
 186        return p;
 187}
 188
 189/* called under rcu_read_lock */
 190void br_flood(struct net_bridge *br, struct sk_buff *skb,
 191              enum br_pkt_type pkt_type, bool local_rcv, bool local_orig)
 192{
 193        struct net_bridge_port *prev = NULL;
 194        struct net_bridge_port *p;
 195
 196        list_for_each_entry_rcu(p, &br->port_list, list) {
 197                /* Do not flood unicast traffic to ports that turn it off, nor
 198                 * other traffic if flood off, except for traffic we originate
 199                 */
 200                switch (pkt_type) {
 201                case BR_PKT_UNICAST:
 202                        if (!(p->flags & BR_FLOOD))
 203                                continue;
 204                        break;
 205                case BR_PKT_MULTICAST:
 206                        if (!(p->flags & BR_MCAST_FLOOD) && skb->dev != br->dev)
 207                                continue;
 208                        break;
 209                case BR_PKT_BROADCAST:
 210                        if (!(p->flags & BR_BCAST_FLOOD) && skb->dev != br->dev)
 211                                continue;
 212                        break;
 213                }
 214
 215                /* Do not flood to ports that enable proxy ARP */
 216                if (p->flags & BR_PROXYARP)
 217                        continue;
 218                if ((p->flags & (BR_PROXYARP_WIFI | BR_NEIGH_SUPPRESS)) &&
 219                    BR_INPUT_SKB_CB(skb)->proxyarp_replied)
 220                        continue;
 221
 222                prev = maybe_deliver(prev, p, skb, local_orig);
 223                if (IS_ERR(prev))
 224                        goto out;
 225        }
 226
 227        if (!prev)
 228                goto out;
 229
 230        if (local_rcv)
 231                deliver_clone(prev, skb, local_orig);
 232        else
 233                __br_forward(prev, skb, local_orig);
 234        return;
 235
 236out:
 237        if (!local_rcv)
 238                kfree_skb(skb);
 239}
 240
 241#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 242static void maybe_deliver_addr(struct net_bridge_port *p, struct sk_buff *skb,
 243                               const unsigned char *addr, bool local_orig)
 244{
 245        struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 246        const unsigned char *src = eth_hdr(skb)->h_source;
 247
 248        if (!should_deliver(p, skb))
 249                return;
 250
 251        /* Even with hairpin, no soliloquies - prevent breaking IPv6 DAD */
 252        if (skb->dev == p->dev && ether_addr_equal(src, addr))
 253                return;
 254
 255        skb = skb_copy(skb, GFP_ATOMIC);
 256        if (!skb) {
 257                dev->stats.tx_dropped++;
 258                return;
 259        }
 260
 261        if (!is_broadcast_ether_addr(addr))
 262                memcpy(eth_hdr(skb)->h_dest, addr, ETH_ALEN);
 263
 264        __br_forward(p, skb, local_orig);
 265}
 266
 267/* called with rcu_read_lock */
 268void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 269                        struct sk_buff *skb,
 270                        bool local_rcv, bool local_orig)
 271{
 272        struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 273        struct net_bridge *br = netdev_priv(dev);
 274        struct net_bridge_port *prev = NULL;
 275        struct net_bridge_port_group *p;
 276        bool allow_mode_include = true;
 277        struct hlist_node *rp;
 278
 279        rp = rcu_dereference(hlist_first_rcu(&br->router_list));
 280        if (mdst) {
 281                p = rcu_dereference(mdst->ports);
 282                if (br_multicast_should_handle_mode(br, mdst->addr.proto) &&
 283                    br_multicast_is_star_g(&mdst->addr))
 284                        allow_mode_include = false;
 285        } else {
 286                p = NULL;
 287        }
 288
 289        while (p || rp) {
 290                struct net_bridge_port *port, *lport, *rport;
 291
 292                lport = p ? p->key.port : NULL;
 293                rport = hlist_entry_safe(rp, struct net_bridge_port, rlist);
 294
 295                if ((unsigned long)lport > (unsigned long)rport) {
 296                        port = lport;
 297
 298                        if (port->flags & BR_MULTICAST_TO_UNICAST) {
 299                                maybe_deliver_addr(lport, skb, p->eth_addr,
 300                                                   local_orig);
 301                                goto delivered;
 302                        }
 303                        if ((!allow_mode_include &&
 304                             p->filter_mode == MCAST_INCLUDE) ||
 305                            (p->flags & MDB_PG_FLAGS_BLOCKED))
 306                                goto delivered;
 307                } else {
 308                        port = rport;
 309                }
 310
 311                prev = maybe_deliver(prev, port, skb, local_orig);
 312                if (IS_ERR(prev))
 313                        goto out;
 314delivered:
 315                if ((unsigned long)lport >= (unsigned long)port)
 316                        p = rcu_dereference(p->next);
 317                if ((unsigned long)rport >= (unsigned long)port)
 318                        rp = rcu_dereference(hlist_next_rcu(rp));
 319        }
 320
 321        if (!prev)
 322                goto out;
 323
 324        if (local_rcv)
 325                deliver_clone(prev, skb, local_orig);
 326        else
 327                __br_forward(prev, skb, local_orig);
 328        return;
 329
 330out:
 331        if (!local_rcv)
 332                kfree_skb(skb);
 333}
 334#endif
 335