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/kernel.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/if_vlan.h>
  19 #include <linux/netfilter_bridge.h>
  20 #include "br_private.h"
  21
  22 /* Don't forward packets to originating port or forwarding diasabled */
  23 static inline int should_deliver(const struct net_bridge_port *p,
  24                                  const struct sk_buff *skb)
  25 {
  26         return (((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
  27                 p->state == BR_STATE_FORWARDING);
  28 }
  29
  30 static inline unsigned packet_length(const struct sk_buff *skb)
  31 {
  32         return skb->len - (skb->protocol == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
  33 }
  34
  35 int br_dev_queue_push_xmit(struct sk_buff *skb)
  36 {
  37         /* drop mtu oversized packets except gso */
  38         if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
  39                 kfree_skb(skb);
  40         else {
  41                 /* ip_refrag calls ip_fragment, doesn't copy the MAC header. */
  42                 if (nf_bridge_maybe_copy_header(skb))
  43                         kfree_skb(skb);
  44                 else {
  45                         skb_push(skb, ETH_HLEN);
  46
  47                         dev_queue_xmit(skb);
  48                 }
  49         }
  50
  51         return 0;
  52 }
  53
  54 int br_forward_finish(struct sk_buff *skb)
  55 {
  56         return NF_HOOK(PF_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
  57                        br_dev_queue_push_xmit);
  58
  59 }
  60
  61 static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  62 {
  63         skb->dev = to->dev;
  64         NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  65                         br_forward_finish);
  66 }
  67
  68 static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
  69 {
  70         struct net_device *indev;
  71
  72         if (skb_warn_if_lro(skb)) {
  73                 kfree_skb(skb);
  74                 return;
  75         }
  76
  77         indev = skb->dev;
  78         skb->dev = to->dev;
  79         skb_forward_csum(skb);
  80
  81         NF_HOOK(PF_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
  82                         br_forward_finish);
  83 }
  84
  85 /* called with rcu_read_lock */
  86 void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  87 {
  88         if (should_deliver(to, skb)) {
  89                 __br_deliver(to, skb);
  90                 return;
  91         }
  92
  93         kfree_skb(skb);
  94 }
  95
  96 /* called with rcu_read_lock */
  97 void br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
  98 {
  99         if (should_deliver(to, skb)) {
 100                 __br_forward(to, skb);
 101                 return;
 102         }
 103
 104         kfree_skb(skb);
 105 }
 106
 107 static int deliver_clone(struct net_bridge_port *prev, struct sk_buff *skb,
 108                          void (*__packet_hook)(const struct net_bridge_port *p,
 109                                                struct sk_buff *skb))
 110 {
 111         skb = skb_clone(skb, GFP_ATOMIC);
 112         if (!skb) {
 113                 struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 114
 115                 dev->stats.tx_dropped++;
 116                 return -ENOMEM;
 117         }
 118
 119         __packet_hook(prev, skb);
 120         return 0;
 121 }
 122
 123 static struct net_bridge_port *maybe_deliver(
 124         struct net_bridge_port *prev, struct net_bridge_port *p,
 125         struct sk_buff *skb,
 126         void (*__packet_hook)(const struct net_bridge_port *p,
 127                               struct sk_buff *skb))
 128 {
 129         int err;
 130
 131         if (!should_deliver(p, skb))
 132                 return prev;
 133
 134         if (!prev)
 135                 goto out;
 136
 137         err = deliver_clone(prev, skb, __packet_hook);
 138         if (err)
 139                 return ERR_PTR(err);
 140
 141 out:
 142         return p;
 143 }
 144
 145 /* called under bridge lock */
 146 static void br_flood(struct net_bridge *br, struct sk_buff *skb,
 147                      struct sk_buff *skb0,
 148                      void (*__packet_hook)(const struct net_bridge_port *p,
 149                                            struct sk_buff *skb))
 150 {
 151         struct net_bridge_port *p;
 152         struct net_bridge_port *prev;
 153
 154         prev = NULL;
 155
 156         list_for_each_entry_rcu(p, &br->port_list, list) {
 157                 prev = maybe_deliver(prev, p, skb, __packet_hook);
 158                 if (IS_ERR(prev))
 159                         goto out;
 160         }
 161
 162         if (!prev)
 163                 goto out;
 164
 165         if (skb0)
 166                 deliver_clone(prev, skb, __packet_hook);
 167         else
 168                 __packet_hook(prev, skb);
 169         return;
 170
 171 out:
 172         if (!skb0)
 173                 kfree_skb(skb);
 174 }
 175
 176
 177 /* called with rcu_read_lock */
 178 void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
 179 {
 180         br_flood(br, skb, NULL, __br_deliver);
 181 }
 182
 183 /* called under bridge lock */
 184 void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
 185                       struct sk_buff *skb2)
 186 {
 187         br_flood(br, skb, skb2, __br_forward);
 188 }