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         /* drop mtu oversized packets except gso */
  45         if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
  46                 kfree_skb(skb);
  47         else {
  48                 /* ip_fragment doesn't copy the MAC header */
  49                 if (nf_bridge_maybe_copy_header(skb))
  50                         kfree_skb(skb);
  51                 else {
  52                         skb_push(skb, ETH_HLEN);
  53                         dev_queue_xmit(skb);
  54                 }
  55         }
  56
  57         return 0;
  58 }
  59
  60 int br_forward_finish(struct sk_buff *skb)
  61 {
  62         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
  63                        br_dev_queue_push_xmit);
  64
  65 }
  66
  67 static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  68 {
  69         skb->dev = to->dev;
  70
  71         if (unlikely(netpoll_tx_running(to->dev))) {
  72                 if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
  73                         kfree_skb(skb);
  74                 else {
  75                         skb_push(skb, ETH_HLEN);
  76                         br_netpoll_send_skb(to, skb);
  77                 }
  78                 return;
  79         }
  80
  81         NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  82                 br_forward_finish);
  83 }
  84
  85 static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
  86 {
  87         struct net_device *indev;
  88
  89         if (skb_warn_if_lro(skb)) {
  90                 kfree_skb(skb);
  91                 return;
  92         }
  93
  94         indev = skb->dev;
  95         skb->dev = to->dev;
  96         skb_forward_csum(skb);
  97
  98         NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
  99                 br_forward_finish);
 100 }
 101
 102 /* called with rcu_read_lock */
 103 void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
 104 {
 105         if (should_deliver(to, skb)) {
 106                 __br_deliver(to, skb);
 107                 return;
 108         }
 109
 110         kfree_skb(skb);
 111 }
 112
 113 /* called with rcu_read_lock */
 114 void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
 115 {
 116         if (should_deliver(to, skb)) {
 117                 if (skb0)
 118                         deliver_clone(to, skb, __br_forward);
 119                 else
 120                         __br_forward(to, skb);
 121                 return;
 122         }
 123
 124         if (!skb0)
 125                 kfree_skb(skb);
 126 }
 127
 128 static int deliver_clone(const struct net_bridge_port *prev,
 129                          struct sk_buff *skb,
 130                          void (*__packet_hook)(const struct net_bridge_port *p,
 131                                                struct sk_buff *skb))
 132 {
 133         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 134
 135         skb = skb_clone(skb, GFP_ATOMIC);
 136         if (!skb) {
 137                 dev->stats.tx_dropped++;
 138                 return -ENOMEM;
 139         }
 140
 141         __packet_hook(prev, skb);
 142         return 0;
 143 }
 144
 145 static struct net_bridge_port *maybe_deliver(
 146         struct net_bridge_port *prev, struct net_bridge_port *p,
 147         struct sk_buff *skb,
 148         void (*__packet_hook)(const struct net_bridge_port *p,
 149                               struct sk_buff *skb))
 150 {
 151         int err;
 152
 153         if (!should_deliver(p, skb))
 154                 return prev;
 155
 156         if (!prev)
 157                 goto out;
 158
 159         err = deliver_clone(prev, skb, __packet_hook);
 160         if (err)
 161                 return ERR_PTR(err);
 162
 163 out:
 164         return p;
 165 }
 166
 167 /* called under bridge lock */
 168 static void br_flood(struct net_bridge *br, struct sk_buff *skb,
 169                      struct sk_buff *skb0,
 170                      void (*__packet_hook)(const struct net_bridge_port *p,
 171                                            struct sk_buff *skb))
 172 {
 173         struct net_bridge_port *p;
 174         struct net_bridge_port *prev;
 175
 176         prev = NULL;
 177
 178         list_for_each_entry_rcu(p, &br->port_list, list) {
 179                 prev = maybe_deliver(prev, p, skb, __packet_hook);
 180                 if (IS_ERR(prev))
 181                         goto out;
 182         }
 183
 184         if (!prev)
 185                 goto out;
 186
 187         if (skb0)
 188                 deliver_clone(prev, skb, __packet_hook);
 189         else
 190                 __packet_hook(prev, skb);
 191         return;
 192
 193 out:
 194         if (!skb0)
 195                 kfree_skb(skb);
 196 }
 197
 198
 199 /* called with rcu_read_lock */
 200 void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
 201 {
 202         br_flood(br, skb, NULL, __br_deliver);
 203 }
 204
 205 /* called under bridge lock */
 206 void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
 207                       struct sk_buff *skb2)
 208 {
 209         br_flood(br, skb, skb2, __br_forward);
 210 }
 211
 212 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 213 /* called with rcu_read_lock */
 214 static void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
 215                                struct sk_buff *skb, struct sk_buff *skb0,
 216                                void (*__packet_hook)(
 217                                         const struct net_bridge_port *p,
 218                                         struct sk_buff *skb))
 219 {
 220         struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 221         struct net_bridge *br = netdev_priv(dev);
 222         struct net_bridge_port *prev = NULL;
 223         struct net_bridge_port_group *p;
 224         struct hlist_node *rp;
 225
 226         rp = rcu_dereference(br->router_list.first);
 227         p = mdst ? rcu_dereference(mdst->ports) : NULL;
 228         while (p || rp) {
 229                 struct net_bridge_port *port, *lport, *rport;
 230
 231                 lport = p ? p->port : NULL;
 232                 rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
 233                              NULL;
 234
 235                 port = (unsigned long)lport > (unsigned long)rport ?
 236                        lport : rport;
 237
 238                 prev = maybe_deliver(prev, port, skb, __packet_hook);
 239                 if (IS_ERR(prev))
 240                         goto out;
 241
 242                 if ((unsigned long)lport >= (unsigned long)port)
 243                         p = rcu_dereference(p->next);
 244                 if ((unsigned long)rport >= (unsigned long)port)
 245                         rp = rcu_dereference(rp->next);
 246         }
 247
 248         if (!prev)
 249                 goto out;
 250
 251         if (skb0)
 252                 deliver_clone(prev, skb, __packet_hook);
 253         else
 254                 __packet_hook(prev, skb);
 255         return;
 256
 257 out:
 258         if (!skb0)
 259                 kfree_skb(skb);
 260 }
 261
 262 /* called with rcu_read_lock */
 263 void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
 264                           struct sk_buff *skb)
 265 {
 266         br_multicast_flood(mdst, skb, NULL, __br_deliver);
 267 }
 268
 269 /* called with rcu_read_lock */
 270 void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
 271                           struct sk_buff *skb, struct sk_buff *skb2)
 272 {
 273         br_multicast_flood(mdst, skb, skb2, __br_forward);
 274 }
 275 #endif