net/bridge/br_forward.c

   1 /*
   2  *      Forwarding decision
   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/err.h>
  15 #include <linux/slab.h>
  16 #include <linux/kernel.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/netpoll.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/if_vlan.h>
  21 #include <linux/netfilter_bridge.h>
  22 #include "br_private.h"
  23
  24 static int deliver_clone(const struct net_bridge_port *prev,
  25                          struct sk_buff *skb,
  26                          void (*__packet_hook)(const struct net_bridge_port *p,
  27                                                struct sk_buff *skb));
  28
  29 /* Don't forward packets to originating port or forwarding diasabled */
  30 static inline int should_deliver(const struct net_bridge_port *p,
  31                                  const struct sk_buff *skb)
  32 {
  33         return (((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
  34                 p->state == BR_STATE_FORWARDING);
  35 }
  36
  37 static inline unsigned packet_length(const struct sk_buff *skb)
  38 {
  39         return skb->len - (skb->protocol == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
  40 }
  41
  42 int br_dev_queue_push_xmit(struct sk_buff *skb)
  43 {
  44         /* ip_fragment doesn't copy the MAC header */
  45         if (nf_bridge_maybe_copy_header(skb) ||
  46             (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))) {
  47                 kfree_skb(skb);
  48         } else {
  49                 skb_push(skb, ETH_HLEN);
  50                 dev_queue_xmit(skb);
  51         }
  52
  53         return 0;
  54 }
  55
  56 int br_forward_finish(struct sk_buff *skb)
  57 {
  58         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
  59                        br_dev_queue_push_xmit);
  60
  61 }
  62
  63 static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  64 {
  65         skb->dev = to->dev;
  66
  67         if (unlikely(netpoll_tx_running(to->dev))) {
  68                 if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
  69                         kfree_skb(skb);
  70                 else {
  71                         skb_push(skb, ETH_HLEN);
  72                         br_netpoll_send_skb(to, skb);
  73                 }
  74                 return;
  75         }
  76
  77         NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  78                 br_forward_finish);
  79 }
  80
  81 static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
  82 {
  83         struct net_device *indev;
  84
  85         if (skb_warn_if_lro(skb)) {
  86                 kfree_skb(skb);
  87                 return;
  88         }
  89
  90         indev = skb->dev;
  91         skb->dev = to->dev;
  92         skb_forward_csum(skb);
  93
  94         NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
  95                 br_forward_finish);
  96 }
  97
  98 /* called with rcu_read_lock */
  99 void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
 100 {
 101         if (should_deliver(to, skb)) {
 102                 __br_deliver(to, skb);
 103                 return;
 104         }
 105
 106         kfree_skb(skb);
 107 }
 108
 109 /* called with rcu_read_lock */
 110 void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
 111 {
 112         if (should_deliver(to, skb)) {
 113                 if (skb0)
 114                         deliver_clone(to, skb, __br_forward);
 115                 else
 116                         __br_forward(to, skb);
 117                 return;
 118         }
 119
 120         if (!skb0)
 121                 kfree_skb(skb);
 122 }
 123
 124 static int deliver_clone(const struct net_bridge_port *prev,
 125                          struct sk_buff *skb,
 126                          void (*__packet_hook)(const struct net_bridge_port *p,
 127                                                struct sk_buff *skb))
 128 {
 129         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 130
 131         skb = skb_clone(skb, GFP_ATOMIC);
 132         if (!skb) {
 133                 dev->stats.tx_dropped++;
 134                 return -ENOMEM;
 135         }
 136
 137         __packet_hook(prev, skb);
 138         return 0;
 139 }
 140
 141 static struct net_bridge_port *maybe_deliver(
 142         struct net_bridge_port *prev, struct net_bridge_port *p,
 143         struct sk_buff *skb,
 144         void (*__packet_hook)(const struct net_bridge_port *p,
 145                               struct sk_buff *skb))
 146 {
 147         int err;
 148
 149         if (!should_deliver(p, skb))
 150                 return prev;
 151
 152         if (!prev)
 153                 goto out;
 154
 155         err = deliver_clone(prev, skb, __packet_hook);
 156         if (err)
 157                 return ERR_PTR(err);
 158
 159 out:
 160         return p;
 161 }
 162
 163 /* called under bridge lock */
 164 static void br_flood(struct net_bridge *br, struct sk_buff *skb,
 165                      struct sk_buff *skb0,
 166                      void (*__packet_hook)(const struct net_bridge_port *p,
 167                                            struct sk_buff *skb))
 168 {
 169         struct net_bridge_port *p;
 170         struct net_bridge_port *prev;
 171
 172         prev = NULL;
 173
 174         list_for_each_entry_rcu(p, &br->port_list, list) {
 175                 prev = maybe_deliver(prev, p, skb, __packet_hook);
 176                 if (IS_ERR(prev))
 177                         goto out;
 178         }
 179
 180         if (!prev)
 181                 goto out;
 182
 183         if (skb0)
 184                 deliver_clone(prev, skb, __packet_hook);
 185         else
 186                 __packet_hook(prev, skb);
 187         return;
 188
 189 out:
 190         if (!skb0)
 191                 kfree_skb(skb);
 192 }
 193
 194
 195 /* called with rcu_read_lock */
 196 void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
 197 {
 198         br_flood(br, skb, NULL, __br_deliver);
 199 }
 200
 201 /* called under bridge lock */
 202 void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
 203                       struct sk_buff *skb2)
 204 {
 205         br_flood(br, skb, skb2, __br_forward);
 206 }
 207
 208 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 209 /* called with rcu_read_lock */
 210 static void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 211                                struct sk_buff *skb, struct sk_buff *skb0,
 212                                void (*__packet_hook)(
 213                                         const struct net_bridge_port *p,
 214                                         struct sk_buff *skb))
 215 {
 216         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 217         struct net_bridge *br = netdev_priv(dev);
 218         struct net_bridge_port *prev = NULL;
 219         struct net_bridge_port_group *p;
 220         struct hlist_node *rp;
 221
 222         rp = rcu_dereference(hlist_first_rcu(&br->router_list));
 223         p = mdst ? rcu_dereference(mdst->ports) : NULL;
 224         while (p || rp) {
 225                 struct net_bridge_port *port, *lport, *rport;
 226
 227                 lport = p ? p->port : NULL;
 228                 rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
 229                              NULL;
 230
 231                 port = (unsigned long)lport > (unsigned long)rport ?
 232                        lport : rport;
 233
 234                 prev = maybe_deliver(prev, port, skb, __packet_hook);
 235                 if (IS_ERR(prev))
 236                         goto out;
 237
 238                 if ((unsigned long)lport >= (unsigned long)port)
 239                         p = rcu_dereference(p->next);
 240                 if ((unsigned long)rport >= (unsigned long)port)
 241                         rp = rcu_dereference(hlist_next_rcu(rp));
 242         }
 243
 244         if (!prev)
 245                 goto out;
 246
 247         if (skb0)
 248                 deliver_clone(prev, skb, __packet_hook);
 249         else
 250                 __packet_hook(prev, skb);
 251         return;
 252
 253 out:
 254         if (!skb0)
 255                 kfree_skb(skb);
 256 }
 257
 258 /* called with rcu_read_lock */
 259 void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
 260                           struct sk_buff *skb)
 261 {
 262         br_multicast_flood(mdst, skb, NULL, __br_deliver);
 263 }
 264
 265 /* called with rcu_read_lock */
 266 void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
 267                           struct sk_buff *skb, struct sk_buff *skb2)
 268 {
 269         br_multicast_flood(mdst, skb, skb2, __br_forward);
 270 }
 271 #endif