xref: /openbmc/linux/net/bridge/br_input.c (revision c819e2cf)
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 <linux/neighbour.h>
20 #include <net/arp.h>
21 #include <linux/export.h>
22 #include <linux/rculist.h>
23 #include "br_private.h"
24 
25 /* Hook for brouter */
26 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
27 EXPORT_SYMBOL(br_should_route_hook);
28 
29 static int br_pass_frame_up(struct sk_buff *skb)
30 {
31 	struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
32 	struct net_bridge *br = netdev_priv(brdev);
33 	struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
34 	struct net_port_vlans *pv;
35 
36 	u64_stats_update_begin(&brstats->syncp);
37 	brstats->rx_packets++;
38 	brstats->rx_bytes += skb->len;
39 	u64_stats_update_end(&brstats->syncp);
40 
41 	/* Bridge is just like any other port.  Make sure the
42 	 * packet is allowed except in promisc modue when someone
43 	 * may be running packet capture.
44 	 */
45 	pv = br_get_vlan_info(br);
46 	if (!(brdev->flags & IFF_PROMISC) &&
47 	    !br_allowed_egress(br, pv, skb)) {
48 		kfree_skb(skb);
49 		return NET_RX_DROP;
50 	}
51 
52 	indev = skb->dev;
53 	skb->dev = brdev;
54 	skb = br_handle_vlan(br, pv, skb);
55 	if (!skb)
56 		return NET_RX_DROP;
57 
58 	return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
59 		       netif_receive_skb);
60 }
61 
62 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
63 			    u16 vid)
64 {
65 	struct net_device *dev = br->dev;
66 	struct neighbour *n;
67 	struct arphdr *parp;
68 	u8 *arpptr, *sha;
69 	__be32 sip, tip;
70 
71 	if (dev->flags & IFF_NOARP)
72 		return;
73 
74 	if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
75 		dev->stats.tx_dropped++;
76 		return;
77 	}
78 	parp = arp_hdr(skb);
79 
80 	if (parp->ar_pro != htons(ETH_P_IP) ||
81 	    parp->ar_op != htons(ARPOP_REQUEST) ||
82 	    parp->ar_hln != dev->addr_len ||
83 	    parp->ar_pln != 4)
84 		return;
85 
86 	arpptr = (u8 *)parp + sizeof(struct arphdr);
87 	sha = arpptr;
88 	arpptr += dev->addr_len;	/* sha */
89 	memcpy(&sip, arpptr, sizeof(sip));
90 	arpptr += sizeof(sip);
91 	arpptr += dev->addr_len;	/* tha */
92 	memcpy(&tip, arpptr, sizeof(tip));
93 
94 	if (ipv4_is_loopback(tip) ||
95 	    ipv4_is_multicast(tip))
96 		return;
97 
98 	n = neigh_lookup(&arp_tbl, &tip, dev);
99 	if (n) {
100 		struct net_bridge_fdb_entry *f;
101 
102 		if (!(n->nud_state & NUD_VALID)) {
103 			neigh_release(n);
104 			return;
105 		}
106 
107 		f = __br_fdb_get(br, n->ha, vid);
108 		if (f)
109 			arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
110 				 sha, n->ha, sha);
111 
112 		neigh_release(n);
113 	}
114 }
115 
116 /* note: already called with rcu_read_lock */
117 int br_handle_frame_finish(struct sk_buff *skb)
118 {
119 	const unsigned char *dest = eth_hdr(skb)->h_dest;
120 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
121 	struct net_bridge *br;
122 	struct net_bridge_fdb_entry *dst;
123 	struct net_bridge_mdb_entry *mdst;
124 	struct sk_buff *skb2;
125 	bool unicast = true;
126 	u16 vid = 0;
127 
128 	if (!p || p->state == BR_STATE_DISABLED)
129 		goto drop;
130 
131 	if (!br_allowed_ingress(p->br, nbp_get_vlan_info(p), skb, &vid))
132 		goto out;
133 
134 	/* insert into forwarding database after filtering to avoid spoofing */
135 	br = p->br;
136 	if (p->flags & BR_LEARNING)
137 		br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
138 
139 	if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
140 	    br_multicast_rcv(br, p, skb, vid))
141 		goto drop;
142 
143 	if (p->state == BR_STATE_LEARNING)
144 		goto drop;
145 
146 	BR_INPUT_SKB_CB(skb)->brdev = br->dev;
147 
148 	/* The packet skb2 goes to the local host (NULL to skip). */
149 	skb2 = NULL;
150 
151 	if (br->dev->flags & IFF_PROMISC)
152 		skb2 = skb;
153 
154 	dst = NULL;
155 
156 	if (is_broadcast_ether_addr(dest)) {
157 		if (IS_ENABLED(CONFIG_INET) &&
158 		    p->flags & BR_PROXYARP &&
159 		    skb->protocol == htons(ETH_P_ARP))
160 			br_do_proxy_arp(skb, br, vid);
161 
162 		skb2 = skb;
163 		unicast = false;
164 	} else if (is_multicast_ether_addr(dest)) {
165 		mdst = br_mdb_get(br, skb, vid);
166 		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
167 		    br_multicast_querier_exists(br, eth_hdr(skb))) {
168 			if ((mdst && mdst->mglist) ||
169 			    br_multicast_is_router(br))
170 				skb2 = skb;
171 			br_multicast_forward(mdst, skb, skb2);
172 			skb = NULL;
173 			if (!skb2)
174 				goto out;
175 		} else
176 			skb2 = skb;
177 
178 		unicast = false;
179 		br->dev->stats.multicast++;
180 	} else if ((dst = __br_fdb_get(br, dest, vid)) &&
181 			dst->is_local) {
182 		skb2 = skb;
183 		/* Do not forward the packet since it's local. */
184 		skb = NULL;
185 	}
186 
187 	if (skb) {
188 		if (dst) {
189 			dst->used = jiffies;
190 			br_forward(dst->dst, skb, skb2);
191 		} else
192 			br_flood_forward(br, skb, skb2, unicast);
193 	}
194 
195 	if (skb2)
196 		return br_pass_frame_up(skb2);
197 
198 out:
199 	return 0;
200 drop:
201 	kfree_skb(skb);
202 	goto out;
203 }
204 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
205 
206 /* note: already called with rcu_read_lock */
207 static int br_handle_local_finish(struct sk_buff *skb)
208 {
209 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
210 	u16 vid = 0;
211 
212 	/* check if vlan is allowed, to avoid spoofing */
213 	if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
214 		br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
215 	return 0;	 /* process further */
216 }
217 
218 /*
219  * Return NULL if skb is handled
220  * note: already called with rcu_read_lock
221  */
222 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
223 {
224 	struct net_bridge_port *p;
225 	struct sk_buff *skb = *pskb;
226 	const unsigned char *dest = eth_hdr(skb)->h_dest;
227 	br_should_route_hook_t *rhook;
228 
229 	if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
230 		return RX_HANDLER_PASS;
231 
232 	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
233 		goto drop;
234 
235 	skb = skb_share_check(skb, GFP_ATOMIC);
236 	if (!skb)
237 		return RX_HANDLER_CONSUMED;
238 
239 	p = br_port_get_rcu(skb->dev);
240 
241 	if (unlikely(is_link_local_ether_addr(dest))) {
242 		u16 fwd_mask = p->br->group_fwd_mask_required;
243 
244 		/*
245 		 * See IEEE 802.1D Table 7-10 Reserved addresses
246 		 *
247 		 * Assignment		 		Value
248 		 * Bridge Group Address		01-80-C2-00-00-00
249 		 * (MAC Control) 802.3		01-80-C2-00-00-01
250 		 * (Link Aggregation) 802.3	01-80-C2-00-00-02
251 		 * 802.1X PAE address		01-80-C2-00-00-03
252 		 *
253 		 * 802.1AB LLDP 		01-80-C2-00-00-0E
254 		 *
255 		 * Others reserved for future standardization
256 		 */
257 		switch (dest[5]) {
258 		case 0x00:	/* Bridge Group Address */
259 			/* If STP is turned off,
260 			   then must forward to keep loop detection */
261 			if (p->br->stp_enabled == BR_NO_STP ||
262 			    fwd_mask & (1u << dest[5]))
263 				goto forward;
264 			break;
265 
266 		case 0x01:	/* IEEE MAC (Pause) */
267 			goto drop;
268 
269 		default:
270 			/* Allow selective forwarding for most other protocols */
271 			fwd_mask |= p->br->group_fwd_mask;
272 			if (fwd_mask & (1u << dest[5]))
273 				goto forward;
274 		}
275 
276 		/* Deliver packet to local host only */
277 		if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
278 			    NULL, br_handle_local_finish)) {
279 			return RX_HANDLER_CONSUMED; /* consumed by filter */
280 		} else {
281 			*pskb = skb;
282 			return RX_HANDLER_PASS;	/* continue processing */
283 		}
284 	}
285 
286 forward:
287 	switch (p->state) {
288 	case BR_STATE_FORWARDING:
289 		rhook = rcu_dereference(br_should_route_hook);
290 		if (rhook) {
291 			if ((*rhook)(skb)) {
292 				*pskb = skb;
293 				return RX_HANDLER_PASS;
294 			}
295 			dest = eth_hdr(skb)->h_dest;
296 		}
297 		/* fall through */
298 	case BR_STATE_LEARNING:
299 		if (ether_addr_equal(p->br->dev->dev_addr, dest))
300 			skb->pkt_type = PACKET_HOST;
301 
302 		NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
303 			br_handle_frame_finish);
304 		break;
305 	default:
306 drop:
307 		kfree_skb(skb);
308 	}
309 	return RX_HANDLER_CONSUMED;
310 }
311