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