net/bridge/br_forward.c

   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 */
  21 static 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
  33 int 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             (skb->protocol == htons(ETH_P_8021Q) ||
  43              skb->protocol == htons(ETH_P_8021AD))) {
  44                 int depth;
  45
  46                 if (!__vlan_get_protocol(skb, skb->protocol, &depth))
  47                         goto drop;
  48
  49                 skb_set_network_header(skb, depth);
  50         }
  51
  52         dev_queue_xmit(skb);
  53
  54         return 0;
  55
  56 drop:
  57         kfree_skb(skb);
  58         return 0;
  59 }
  60 EXPORT_SYMBOL_GPL(br_dev_queue_push_xmit);
  61
  62 int br_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  63 {
  64         skb->tstamp = 0;
  65         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING,
  66                        net, sk, skb, NULL, skb->dev,
  67                        br_dev_queue_push_xmit);
  68
  69 }
  70 EXPORT_SYMBOL_GPL(br_forward_finish);
  71
  72 static void __br_forward(const struct net_bridge_port *to,
  73                          struct sk_buff *skb, bool local_orig)
  74 {
  75         struct net_bridge_vlan_group *vg;
  76         struct net_device *indev;
  77         struct net *net;
  78         int br_hook;
  79
  80         vg = nbp_vlan_group_rcu(to);
  81         skb = br_handle_vlan(to->br, to, vg, skb);
  82         if (!skb)
  83                 return;
  84
  85         indev = skb->dev;
  86         skb->dev = to->dev;
  87         if (!local_orig) {
  88                 if (skb_warn_if_lro(skb)) {
  89                         kfree_skb(skb);
  90                         return;
  91                 }
  92                 br_hook = NF_BR_FORWARD;
  93                 skb_forward_csum(skb);
  94                 net = dev_net(indev);
  95         } else {
  96                 if (unlikely(netpoll_tx_running(to->br->dev))) {
  97                         skb_push(skb, ETH_HLEN);
  98                         if (!is_skb_forwardable(skb->dev, skb))
  99                                 kfree_skb(skb);
 100                         else
 101                                 br_netpoll_send_skb(to, skb);
 102                         return;
 103                 }
 104                 br_hook = NF_BR_LOCAL_OUT;
 105                 net = dev_net(skb->dev);
 106                 indev = NULL;
 107         }
 108
 109         NF_HOOK(NFPROTO_BRIDGE, br_hook,
 110                 net, NULL, skb, indev, skb->dev,
 111                 br_forward_finish);
 112 }
 113
 114 static int deliver_clone(const struct net_bridge_port *prev,
 115                          struct sk_buff *skb, bool local_orig)
 116 {
 117         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 118
 119         skb = skb_clone(skb, GFP_ATOMIC);
 120         if (!skb) {
 121                 dev->stats.tx_dropped++;
 122                 return -ENOMEM;
 123         }
 124
 125         __br_forward(prev, skb, local_orig);
 126         return 0;
 127 }
 128
 129 /**
 130  * br_forward - forward a packet to a specific port
 131  * @to: destination port
 132  * @skb: packet being forwarded
 133  * @local_rcv: packet will be received locally after forwarding
 134  * @local_orig: packet is locally originated
 135  *
 136  * Should be called with rcu_read_lock.
 137  */
 138 void br_forward(const struct net_bridge_port *to,
 139                 struct sk_buff *skb, bool local_rcv, bool local_orig)
 140 {
 141         if (unlikely(!to))
 142                 goto out;
 143
 144         /* redirect to backup link if the destination port is down */
 145         if (rcu_access_pointer(to->backup_port) && !netif_carrier_ok(to->dev)) {
 146                 struct net_bridge_port *backup_port;
 147
 148                 backup_port = rcu_dereference(to->backup_port);
 149                 if (unlikely(!backup_port))
 150                         goto out;
 151                 to = backup_port;
 152         }
 153
 154         if (should_deliver(to, skb)) {
 155                 if (local_rcv)
 156                         deliver_clone(to, skb, local_orig);
 157                 else
 158                         __br_forward(to, skb, local_orig);
 159                 return;
 160         }
 161
 162 out:
 163         if (!local_rcv)
 164                 kfree_skb(skb);
 165 }
 166 EXPORT_SYMBOL_GPL(br_forward);
 167
 168 static struct net_bridge_port *maybe_deliver(
 169         struct net_bridge_port *prev, struct net_bridge_port *p,
 170         struct sk_buff *skb, bool local_orig)
 171 {
 172         u8 igmp_type = br_multicast_igmp_type(skb);
 173         int err;
 174
 175         if (!should_deliver(p, skb))
 176                 return prev;
 177
 178         if (!prev)
 179                 goto out;
 180
 181         err = deliver_clone(prev, skb, local_orig);
 182         if (err)
 183                 return ERR_PTR(err);
 184 out:
 185         br_multicast_count(p->br, p, skb, igmp_type, BR_MCAST_DIR_TX);
 186
 187         return p;
 188 }
 189
 190 /* called under rcu_read_lock */
 191 void br_flood(struct net_bridge *br, struct sk_buff *skb,
 192               enum br_pkt_type pkt_type, bool local_rcv, bool local_orig)
 193 {
 194         struct net_bridge_port *prev = NULL;
 195         struct net_bridge_port *p;
 196
 197         list_for_each_entry_rcu(p, &br->port_list, list) {
 198                 /* Do not flood unicast traffic to ports that turn it off, nor
 199                  * other traffic if flood off, except for traffic we originate
 200                  */
 201                 switch (pkt_type) {
 202                 case BR_PKT_UNICAST:
 203                         if (!(p->flags & BR_FLOOD))
 204                                 continue;
 205                         break;
 206                 case BR_PKT_MULTICAST:
 207                         if (!(p->flags & BR_MCAST_FLOOD) && skb->dev != br->dev)
 208                                 continue;
 209                         break;
 210                 case BR_PKT_BROADCAST:
 211                         if (!(p->flags & BR_BCAST_FLOOD) && skb->dev != br->dev)
 212                                 continue;
 213                         break;
 214                 }
 215
 216                 /* Do not flood to ports that enable proxy ARP */
 217                 if (p->flags & BR_PROXYARP)
 218                         continue;
 219                 if ((p->flags & (BR_PROXYARP_WIFI | BR_NEIGH_SUPPRESS)) &&
 220                     BR_INPUT_SKB_CB(skb)->proxyarp_replied)
 221                         continue;
 222
 223                 prev = maybe_deliver(prev, p, skb, local_orig);
 224                 if (IS_ERR(prev))
 225                         goto out;
 226         }
 227
 228         if (!prev)
 229                 goto out;
 230
 231         if (local_rcv)
 232                 deliver_clone(prev, skb, local_orig);
 233         else
 234                 __br_forward(prev, skb, local_orig);
 235         return;
 236
 237 out:
 238         if (!local_rcv)
 239                 kfree_skb(skb);
 240 }
 241
 242 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 243 static void maybe_deliver_addr(struct net_bridge_port *p, struct sk_buff *skb,
 244                                const unsigned char *addr, bool local_orig)
 245 {
 246         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 247         const unsigned char *src = eth_hdr(skb)->h_source;
 248
 249         if (!should_deliver(p, skb))
 250                 return;
 251
 252         /* Even with hairpin, no soliloquies - prevent breaking IPv6 DAD */
 253         if (skb->dev == p->dev && ether_addr_equal(src, addr))
 254                 return;
 255
 256         skb = skb_copy(skb, GFP_ATOMIC);
 257         if (!skb) {
 258                 dev->stats.tx_dropped++;
 259                 return;
 260         }
 261
 262         if (!is_broadcast_ether_addr(addr))
 263                 memcpy(eth_hdr(skb)->h_dest, addr, ETH_ALEN);
 264
 265         __br_forward(p, skb, local_orig);
 266 }
 267
 268 /* called with rcu_read_lock */
 269 void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 270                         struct sk_buff *skb,
 271                         bool local_rcv, bool local_orig)
 272 {
 273         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 274         struct net_bridge *br = netdev_priv(dev);
 275         struct net_bridge_port *prev = NULL;
 276         struct net_bridge_port_group *p;
 277         struct hlist_node *rp;
 278
 279         rp = rcu_dereference(hlist_first_rcu(&br->router_list));
 280         p = mdst ? rcu_dereference(mdst->ports) : NULL;
 281         while (p || rp) {
 282                 struct net_bridge_port *port, *lport, *rport;
 283
 284                 lport = p ? p->port : NULL;
 285                 rport = hlist_entry_safe(rp, struct net_bridge_port, rlist);
 286
 287                 if ((unsigned long)lport > (unsigned long)rport) {
 288                         port = lport;
 289
 290                         if (port->flags & BR_MULTICAST_TO_UNICAST) {
 291                                 maybe_deliver_addr(lport, skb, p->eth_addr,
 292                                                    local_orig);
 293                                 goto delivered;
 294                         }
 295                 } else {
 296                         port = rport;
 297                 }
 298
 299                 prev = maybe_deliver(prev, port, skb, local_orig);
 300                 if (IS_ERR(prev))
 301                         goto out;
 302 delivered:
 303                 if ((unsigned long)lport >= (unsigned long)port)
 304                         p = rcu_dereference(p->next);
 305                 if ((unsigned long)rport >= (unsigned long)port)
 306                         rp = rcu_dereference(hlist_next_rcu(rp));
 307         }
 308
 309         if (!prev)
 310                 goto out;
 311
 312         if (local_rcv)
 313                 deliver_clone(prev, skb, local_orig);
 314         else
 315                 __br_forward(prev, skb, local_orig);
 316         return;
 317
 318 out:
 319         if (!local_rcv)
 320                 kfree_skb(skb);
 321 }
 322 #endif