Root/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
24static 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 */
30static 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
37static 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
42int br_dev_queue_push_xmit(struct sk_buff *skb)
43{
44    /* ip_fragment doesn't copy the MAC header */
45    if (nf_bridge_maybe_copy_header(skb) ||
46        (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))) {
47        kfree_skb(skb);
48    } else {
49        skb_push(skb, ETH_HLEN);
50        dev_queue_xmit(skb);
51    }
52
53    return 0;
54}
55
56int br_forward_finish(struct sk_buff *skb)
57{
58    return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
59               br_dev_queue_push_xmit);
60
61}
62
63static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
64{
65    skb->dev = to->dev;
66
67    if (unlikely(netpoll_tx_running(to->dev))) {
68        if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
69            kfree_skb(skb);
70        else {
71            skb_push(skb, ETH_HLEN);
72            br_netpoll_send_skb(to, skb);
73        }
74        return;
75    }
76
77    NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
78        br_forward_finish);
79}
80
81static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
82{
83    struct net_device *indev;
84
85    if (skb_warn_if_lro(skb)) {
86        kfree_skb(skb);
87        return;
88    }
89
90    indev = skb->dev;
91    skb->dev = to->dev;
92    skb_forward_csum(skb);
93
94    NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
95        br_forward_finish);
96}
97
98/* called with rcu_read_lock */
99void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
100{
101    if (should_deliver(to, skb)) {
102        __br_deliver(to, skb);
103        return;
104    }
105
106    kfree_skb(skb);
107}
108
109/* called with rcu_read_lock */
110void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
111{
112    if (should_deliver(to, skb)) {
113        if (skb0)
114            deliver_clone(to, skb, __br_forward);
115        else
116            __br_forward(to, skb);
117        return;
118    }
119
120    if (!skb0)
121        kfree_skb(skb);
122}
123
124static int deliver_clone(const struct net_bridge_port *prev,
125             struct sk_buff *skb,
126             void (*__packet_hook)(const struct net_bridge_port *p,
127                           struct sk_buff *skb))
128{
129    struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
130
131    skb = skb_clone(skb, GFP_ATOMIC);
132    if (!skb) {
133        dev->stats.tx_dropped++;
134        return -ENOMEM;
135    }
136
137    __packet_hook(prev, skb);
138    return 0;
139}
140
141static struct net_bridge_port *maybe_deliver(
142    struct net_bridge_port *prev, struct net_bridge_port *p,
143    struct sk_buff *skb,
144    void (*__packet_hook)(const struct net_bridge_port *p,
145                  struct sk_buff *skb))
146{
147    int err;
148
149    if (!should_deliver(p, skb))
150        return prev;
151
152    if (!prev)
153        goto out;
154
155    err = deliver_clone(prev, skb, __packet_hook);
156    if (err)
157        return ERR_PTR(err);
158
159out:
160    return p;
161}
162
163/* called under bridge lock */
164static void br_flood(struct net_bridge *br, struct sk_buff *skb,
165             struct sk_buff *skb0,
166             void (*__packet_hook)(const struct net_bridge_port *p,
167                       struct sk_buff *skb))
168{
169    struct net_bridge_port *p;
170    struct net_bridge_port *prev;
171
172    prev = NULL;
173
174    list_for_each_entry_rcu(p, &br->port_list, list) {
175        prev = maybe_deliver(prev, p, skb, __packet_hook);
176        if (IS_ERR(prev))
177            goto out;
178    }
179
180    if (!prev)
181        goto out;
182
183    if (skb0)
184        deliver_clone(prev, skb, __packet_hook);
185    else
186        __packet_hook(prev, skb);
187    return;
188
189out:
190    if (!skb0)
191        kfree_skb(skb);
192}
193
194
195/* called with rcu_read_lock */
196void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
197{
198    br_flood(br, skb, NULL, __br_deliver);
199}
200
201/* called under bridge lock */
202void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
203              struct sk_buff *skb2)
204{
205    br_flood(br, skb, skb2, __br_forward);
206}
207
208#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
209/* called with rcu_read_lock */
210static void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
211                   struct sk_buff *skb, struct sk_buff *skb0,
212                   void (*__packet_hook)(
213                    const struct net_bridge_port *p,
214                    struct sk_buff *skb))
215{
216    struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
217    struct net_bridge *br = netdev_priv(dev);
218    struct net_bridge_port *prev = NULL;
219    struct net_bridge_port_group *p;
220    struct hlist_node *rp;
221
222    rp = rcu_dereference(hlist_first_rcu(&br->router_list));
223    p = mdst ? rcu_dereference(mdst->ports) : NULL;
224    while (p || rp) {
225        struct net_bridge_port *port, *lport, *rport;
226
227        lport = p ? p->port : NULL;
228        rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
229                 NULL;
230
231        port = (unsigned long)lport > (unsigned long)rport ?
232               lport : rport;
233
234        prev = maybe_deliver(prev, port, skb, __packet_hook);
235        if (IS_ERR(prev))
236            goto out;
237
238        if ((unsigned long)lport >= (unsigned long)port)
239            p = rcu_dereference(p->next);
240        if ((unsigned long)rport >= (unsigned long)port)
241            rp = rcu_dereference(hlist_next_rcu(rp));
242    }
243
244    if (!prev)
245        goto out;
246
247    if (skb0)
248        deliver_clone(prev, skb, __packet_hook);
249    else
250        __packet_hook(prev, skb);
251    return;
252
253out:
254    if (!skb0)
255        kfree_skb(skb);
256}
257
258/* called with rcu_read_lock */
259void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
260              struct sk_buff *skb)
261{
262    br_multicast_flood(mdst, skb, NULL, __br_deliver);
263}
264
265/* called with rcu_read_lock */
266void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
267              struct sk_buff *skb, struct sk_buff *skb2)
268{
269    br_multicast_flood(mdst, skb, skb2, __br_forward);
270}
271#endif
272

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