1 /* 2 * Handle incoming frames 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/slab.h> 15 #include <linux/kernel.h> 16 #include <linux/netdevice.h> 17 #include <linux/etherdevice.h> 18 #include <linux/netfilter_bridge.h> 19 #include "br_private.h" 20 21 /* Bridge group multicast address 802.1d (pg 51). */ 22 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 }; 23 24 static int br_pass_frame_up(struct sk_buff *skb) 25 { 26 struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev; 27 struct net_bridge *br = netdev_priv(brdev); 28 struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats); 29 30 brstats->rx_packets++; 31 brstats->rx_bytes += skb->len; 32 33 indev = skb->dev; 34 skb->dev = brdev; 35 36 return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL, 37 netif_receive_skb); 38 } 39 40 /* note: already called with rcu_read_lock (preempt_disabled) */ 41 int br_handle_frame_finish(struct sk_buff *skb) 42 { 43 const unsigned char *dest = eth_hdr(skb)->h_dest; 44 struct net_bridge_port *p = rcu_dereference(skb->dev->br_port); 45 struct net_bridge *br; 46 struct net_bridge_fdb_entry *dst; 47 struct net_bridge_mdb_entry *mdst; 48 struct sk_buff *skb2; 49 50 if (!p || p->state == BR_STATE_DISABLED) 51 goto drop; 52 53 /* insert into forwarding database after filtering to avoid spoofing */ 54 br = p->br; 55 br_fdb_update(br, p, eth_hdr(skb)->h_source); 56 57 if (is_multicast_ether_addr(dest) && 58 br_multicast_rcv(br, p, skb)) 59 goto drop; 60 61 if (p->state == BR_STATE_LEARNING) 62 goto drop; 63 64 BR_INPUT_SKB_CB(skb)->brdev = br->dev; 65 66 /* The packet skb2 goes to the local host (NULL to skip). */ 67 skb2 = NULL; 68 69 if (br->dev->flags & IFF_PROMISC) 70 skb2 = skb; 71 72 dst = NULL; 73 74 if (is_multicast_ether_addr(dest)) { 75 mdst = br_mdb_get(br, skb); 76 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) { 77 if ((mdst && !hlist_unhashed(&mdst->mglist)) || 78 br_multicast_is_router(br)) 79 skb2 = skb; 80 br_multicast_forward(mdst, skb, skb2); 81 skb = NULL; 82 if (!skb2) 83 goto out; 84 } else 85 skb2 = skb; 86 87 br->dev->stats.multicast++; 88 } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) { 89 skb2 = skb; 90 /* Do not forward the packet since it's local. */ 91 skb = NULL; 92 } 93 94 if (skb) { 95 if (dst) 96 br_forward(dst->dst, skb, skb2); 97 else 98 br_flood_forward(br, skb, skb2); 99 } 100 101 if (skb2) 102 return br_pass_frame_up(skb2); 103 104 out: 105 return 0; 106 drop: 107 kfree_skb(skb); 108 goto out; 109 } 110 111 /* note: already called with rcu_read_lock (preempt_disabled) */ 112 static int br_handle_local_finish(struct sk_buff *skb) 113 { 114 struct net_bridge_port *p = rcu_dereference(skb->dev->br_port); 115 116 if (p) 117 br_fdb_update(p->br, p, eth_hdr(skb)->h_source); 118 return 0; /* process further */ 119 } 120 121 /* Does address match the link local multicast address. 122 * 01:80:c2:00:00:0X 123 */ 124 static inline int is_link_local(const unsigned char *dest) 125 { 126 __be16 *a = (__be16 *)dest; 127 static const __be16 *b = (const __be16 *)br_group_address; 128 static const __be16 m = cpu_to_be16(0xfff0); 129 130 return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0; 131 } 132 133 /* 134 * Called via br_handle_frame_hook. 135 * Return NULL if skb is handled 136 * note: already called with rcu_read_lock (preempt_disabled) 137 */ 138 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb) 139 { 140 const unsigned char *dest = eth_hdr(skb)->h_dest; 141 int (*rhook)(struct sk_buff *skb); 142 143 if (!is_valid_ether_addr(eth_hdr(skb)->h_source)) 144 goto drop; 145 146 skb = skb_share_check(skb, GFP_ATOMIC); 147 if (!skb) 148 return NULL; 149 150 if (unlikely(is_link_local(dest))) { 151 /* Pause frames shouldn't be passed up by driver anyway */ 152 if (skb->protocol == htons(ETH_P_PAUSE)) 153 goto drop; 154 155 /* If STP is turned off, then forward */ 156 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0) 157 goto forward; 158 159 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev, 160 NULL, br_handle_local_finish)) 161 return NULL; /* frame consumed by filter */ 162 else 163 return skb; /* continue processing */ 164 } 165 166 forward: 167 switch (p->state) { 168 case BR_STATE_FORWARDING: 169 rhook = rcu_dereference(br_should_route_hook); 170 if (rhook != NULL) { 171 if (rhook(skb)) 172 return skb; 173 dest = eth_hdr(skb)->h_dest; 174 } 175 /* fall through */ 176 case BR_STATE_LEARNING: 177 if (!compare_ether_addr(p->br->dev->dev_addr, dest)) 178 skb->pkt_type = PACKET_HOST; 179 180 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL, 181 br_handle_frame_finish); 182 break; 183 default: 184 drop: 185 kfree_skb(skb); 186 } 187 return NULL; 188 } 189