1 /******************************************************************************
4 * A two-interface loopback device to emulate a local netfront-netback
5 * connection. This ensures that local packet delivery looks identical
6 * to inter-domain delivery. Most importantly, packets delivered locally
7 * originating from other domains will get *copied* when they traverse this
8 * driver. This prevents unbounded delays in socket-buffer queues from
9 * causing the netback driver to "seize up".
11 * This driver creates a symmetric pair of loopback interfaces with names
12 * vif0.0 and veth0. The intention is that 'vif0.0' is bound to an Ethernet
13 * bridge, just like a proper netback interface, while a local IP interface
14 * is configured on 'veth0'.
16 * As with a real netback interface, vif0.0 is configured with a suitable
17 * dummy MAC address. No default is provided for veth0: a reasonable strategy
18 * is to transfer eth0's MAC address to veth0, and give eth0 a dummy address
19 * (to avoid confusing the Etherbridge).
21 * Copyright (c) 2005 K A Fraser
23 * This program is free software; you can redistribute it and/or
24 * modify it under the terms of the GNU General Public License version 2
25 * as published by the Free Software Foundation; or, when distributed
26 * separately from the Linux kernel or incorporated into other
27 * software packages, subject to the following license:
29 * Permission is hereby granted, free of charge, to any person obtaining a copy
30 * of this source file (the "Software"), to deal in the Software without
31 * restriction, including without limitation the rights to use, copy, modify,
32 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
33 * and to permit persons to whom the Software is furnished to do so, subject to
34 * the following conditions:
36 * The above copyright notice and this permission notice shall be included in
37 * all copies or substantial portions of the Software.
39 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
40 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
41 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
42 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
43 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
44 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
48 #include <linux/config.h>
49 #include <linux/module.h>
50 #include <linux/netdevice.h>
51 #include <linux/inetdevice.h>
52 #include <linux/etherdevice.h>
53 #include <linux/skbuff.h>
54 #include <linux/ethtool.h>
57 static int nloopbacks = 8;
58 module_param(nloopbacks, int, 0);
59 MODULE_PARM_DESC(nloopbacks, "Number of netback-loopback devices to create");
62 struct net_device *loopback_dev;
63 struct net_device_stats stats;
66 static int loopback_open(struct net_device *dev)
68 struct net_private *np = netdev_priv(dev);
69 memset(&np->stats, 0, sizeof(np->stats));
70 netif_start_queue(dev);
74 static int loopback_close(struct net_device *dev)
76 netif_stop_queue(dev);
80 static int loopback_start_xmit(struct sk_buff *skb, struct net_device *dev)
82 struct net_private *np = netdev_priv(dev);
84 dst_release(skb->dst);
89 np->stats.tx_bytes += skb->len;
90 np->stats.tx_packets++;
92 /* Switch to loopback context. */
93 dev = np->loopback_dev;
94 np = netdev_priv(dev);
96 np->stats.rx_bytes += skb->len;
97 np->stats.rx_packets++;
99 if (skb->ip_summed == CHECKSUM_HW) {
100 /* Defer checksum calculation. */
101 skb->proto_csum_blank = 1;
102 /* Must be a local packet: assert its integrity. */
103 skb->proto_data_valid = 1;
106 skb->ip_summed = skb->proto_data_valid ?
107 CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
109 skb->pkt_type = PACKET_HOST; /* overridden by eth_type_trans() */
110 skb->protocol = eth_type_trans(skb, dev);
112 dev->last_rx = jiffies;
118 static struct net_device_stats *loopback_get_stats(struct net_device *dev)
120 struct net_private *np = netdev_priv(dev);
124 static struct ethtool_ops network_ethtool_ops =
126 .get_tx_csum = ethtool_op_get_tx_csum,
127 .set_tx_csum = ethtool_op_set_tx_csum,
128 .get_sg = ethtool_op_get_sg,
129 .set_sg = ethtool_op_set_sg,
130 .get_tso = ethtool_op_get_tso,
131 .set_tso = ethtool_op_set_tso,
132 .get_link = ethtool_op_get_link,
136 * Nothing to do here. Virtual interface is point-to-point and the
137 * physical interface is probably promiscuous anyway.
139 static void loopback_set_multicast_list(struct net_device *dev)
143 static void loopback_construct(struct net_device *dev, struct net_device *lo)
145 struct net_private *np = netdev_priv(dev);
147 np->loopback_dev = lo;
149 dev->open = loopback_open;
150 dev->stop = loopback_close;
151 dev->hard_start_xmit = loopback_start_xmit;
152 dev->get_stats = loopback_get_stats;
153 dev->set_multicast_list = loopback_set_multicast_list;
154 dev->change_mtu = NULL; /* allow arbitrary mtu */
156 dev->tx_queue_len = 0;
158 dev->features = (NETIF_F_HIGHDMA |
164 SET_ETHTOOL_OPS(dev, &network_ethtool_ops);
167 * We do not set a jumbo MTU on the interface. Otherwise the network
168 * stack will try to send large packets that will get dropped by the
169 * Ethernet bridge (unless the physical Ethernet interface is
170 * configured to transfer jumbo packets). If a larger MTU is desired
171 * then the system administrator can specify it using the 'ifconfig'
174 /*dev->mtu = 16*1024;*/
177 static int __init make_loopback(int i)
179 struct net_device *dev1, *dev2;
180 char dev_name[IFNAMSIZ];
183 sprintf(dev_name, "vif0.%d", i);
184 dev1 = alloc_netdev(sizeof(struct net_private), dev_name, ether_setup);
188 sprintf(dev_name, "veth%d", i);
189 dev2 = alloc_netdev(sizeof(struct net_private), dev_name, ether_setup);
193 loopback_construct(dev1, dev2);
194 loopback_construct(dev2, dev1);
197 * Initialise a dummy MAC address for the 'dummy backend' interface. We
198 * choose the numerically largest non-broadcast address to prevent the
199 * address getting stolen by an Ethernet bridge for STP purposes.
201 memset(dev1->dev_addr, 0xFF, ETH_ALEN);
202 dev1->dev_addr[0] &= ~0x01;
204 if ((err = register_netdev(dev1)) != 0)
207 if ((err = register_netdev(dev2)) != 0) {
208 unregister_netdev(dev1);
221 static void __init clean_loopback(int i)
223 struct net_device *dev1, *dev2;
224 char dev_name[IFNAMSIZ];
226 sprintf(dev_name, "vif0.%d", i);
227 dev1 = dev_get_by_name(dev_name);
228 sprintf(dev_name, "veth%d", i);
229 dev2 = dev_get_by_name(dev_name);
231 unregister_netdev(dev2);
232 unregister_netdev(dev1);
238 static int __init loopback_init(void)
242 for (i = 0; i < nloopbacks; i++)
243 if ((err = make_loopback(i)) != 0)
249 module_init(loopback_init);
251 static void __exit loopback_exit(void)
255 for (i = nloopbacks; i-- > 0; )
259 module_exit(loopback_exit);
261 MODULE_LICENSE("Dual BSD/GPL");