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9a4d105de7
These pernet_operations have only init() method. It allocates memory for net_device, calls register_netdev() and assigns net::loopback_dev. register_netdev() is allowed be used without additional locks, as it's synchronized on rtnl_lock(). There are many examples of using this functon directly from ioctl(). The only difference, compared to ioctl(), is that net is not completely alive at this moment. But it looks like, there is no way for parallel pernet_operations to dereference the net_device, as the most of struct net_device lists, where it's linked, are related to net, and the net is not liked. The exceptions are net_device::unreg_list, close_list, todo_list, used for unregistration, and ::link_watch_list, where net_device may be linked to global lists. Unregistration of loopback_dev obviously can't happen, when loopback_net_init() is executing, as the net as alive. It occurs in default_device_ops, which currently requires net_mutex, and it behaves as a barrier at the moment. It will be considered in next patch. Speaking about link_watch_list, it seems, there is no way for loopback_dev at time of registration to be linked in lweventlist and be available for another pernet_operations. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Acked-by: Andrei Vagin <avagin@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net>
234 lines
5.9 KiB
C
234 lines
5.9 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Pseudo-driver for the loopback interface.
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*
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* Version: @(#)loopback.c 1.0.4b 08/16/93
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Donald Becker, <becker@scyld.com>
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*
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* Alan Cox : Fixed oddments for NET3.014
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* Alan Cox : Rejig for NET3.029 snap #3
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* Alan Cox : Fixed NET3.029 bugs and sped up
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* Larry McVoy : Tiny tweak to double performance
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* Alan Cox : Backed out LMV's tweak - the linux mm
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* can't take it...
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* Michael Griffith: Don't bother computing the checksums
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* on packets received on the loopback
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* interface.
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* Alexey Kuznetsov: Potential hang under some extreme
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* cases removed.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/jiffies.h>
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#include <linux/module.h>
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#include <linux/interrupt.h>
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#include <linux/fs.h>
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#include <linux/types.h>
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#include <linux/string.h>
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#include <linux/socket.h>
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#include <linux/errno.h>
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#include <linux/fcntl.h>
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#include <linux/in.h>
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#include <linux/uaccess.h>
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#include <linux/io.h>
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#include <linux/inet.h>
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#include <linux/netdevice.h>
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#include <linux/etherdevice.h>
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#include <linux/skbuff.h>
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#include <linux/ethtool.h>
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#include <net/sock.h>
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#include <net/checksum.h>
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#include <linux/if_ether.h> /* For the statistics structure. */
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#include <linux/if_arp.h> /* For ARPHRD_ETHER */
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#include <linux/ip.h>
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#include <linux/tcp.h>
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#include <linux/percpu.h>
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#include <linux/net_tstamp.h>
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#include <net/net_namespace.h>
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#include <linux/u64_stats_sync.h>
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struct pcpu_lstats {
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u64 packets;
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u64 bytes;
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struct u64_stats_sync syncp;
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};
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/* The higher levels take care of making this non-reentrant (it's
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* called with bh's disabled).
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*/
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static netdev_tx_t loopback_xmit(struct sk_buff *skb,
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struct net_device *dev)
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{
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struct pcpu_lstats *lb_stats;
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int len;
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skb_tx_timestamp(skb);
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skb_orphan(skb);
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/* Before queueing this packet to netif_rx(),
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* make sure dst is refcounted.
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*/
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skb_dst_force(skb);
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skb->protocol = eth_type_trans(skb, dev);
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/* it's OK to use per_cpu_ptr() because BHs are off */
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lb_stats = this_cpu_ptr(dev->lstats);
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len = skb->len;
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if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
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u64_stats_update_begin(&lb_stats->syncp);
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lb_stats->bytes += len;
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lb_stats->packets++;
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u64_stats_update_end(&lb_stats->syncp);
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}
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return NETDEV_TX_OK;
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}
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static void loopback_get_stats64(struct net_device *dev,
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struct rtnl_link_stats64 *stats)
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{
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u64 bytes = 0;
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u64 packets = 0;
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int i;
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for_each_possible_cpu(i) {
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const struct pcpu_lstats *lb_stats;
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u64 tbytes, tpackets;
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unsigned int start;
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lb_stats = per_cpu_ptr(dev->lstats, i);
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do {
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start = u64_stats_fetch_begin_irq(&lb_stats->syncp);
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tbytes = lb_stats->bytes;
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tpackets = lb_stats->packets;
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} while (u64_stats_fetch_retry_irq(&lb_stats->syncp, start));
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bytes += tbytes;
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packets += tpackets;
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}
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stats->rx_packets = packets;
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stats->tx_packets = packets;
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stats->rx_bytes = bytes;
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stats->tx_bytes = bytes;
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}
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static u32 always_on(struct net_device *dev)
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{
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return 1;
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}
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static int loopback_get_ts_info(struct net_device *netdev,
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struct ethtool_ts_info *ts_info)
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{
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ts_info->so_timestamping = SOF_TIMESTAMPING_TX_SOFTWARE |
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SOF_TIMESTAMPING_RX_SOFTWARE |
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SOF_TIMESTAMPING_SOFTWARE;
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ts_info->phc_index = -1;
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return 0;
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};
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static const struct ethtool_ops loopback_ethtool_ops = {
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.get_link = always_on,
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.get_ts_info = loopback_get_ts_info,
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};
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static int loopback_dev_init(struct net_device *dev)
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{
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dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
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if (!dev->lstats)
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return -ENOMEM;
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return 0;
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}
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static void loopback_dev_free(struct net_device *dev)
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{
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dev_net(dev)->loopback_dev = NULL;
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free_percpu(dev->lstats);
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}
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static const struct net_device_ops loopback_ops = {
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.ndo_init = loopback_dev_init,
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.ndo_start_xmit = loopback_xmit,
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.ndo_get_stats64 = loopback_get_stats64,
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.ndo_set_mac_address = eth_mac_addr,
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};
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/* The loopback device is special. There is only one instance
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* per network namespace.
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*/
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static void loopback_setup(struct net_device *dev)
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{
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dev->mtu = 64 * 1024;
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dev->hard_header_len = ETH_HLEN; /* 14 */
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dev->min_header_len = ETH_HLEN; /* 14 */
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dev->addr_len = ETH_ALEN; /* 6 */
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dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
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dev->flags = IFF_LOOPBACK;
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dev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
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netif_keep_dst(dev);
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dev->hw_features = NETIF_F_GSO_SOFTWARE;
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dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
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| NETIF_F_GSO_SOFTWARE
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| NETIF_F_HW_CSUM
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| NETIF_F_RXCSUM
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| NETIF_F_SCTP_CRC
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| NETIF_F_HIGHDMA
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| NETIF_F_LLTX
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| NETIF_F_NETNS_LOCAL
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| NETIF_F_VLAN_CHALLENGED
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| NETIF_F_LOOPBACK;
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dev->ethtool_ops = &loopback_ethtool_ops;
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dev->header_ops = ð_header_ops;
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dev->netdev_ops = &loopback_ops;
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dev->needs_free_netdev = true;
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dev->priv_destructor = loopback_dev_free;
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}
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/* Setup and register the loopback device. */
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static __net_init int loopback_net_init(struct net *net)
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{
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struct net_device *dev;
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int err;
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err = -ENOMEM;
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dev = alloc_netdev(0, "lo", NET_NAME_UNKNOWN, loopback_setup);
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if (!dev)
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goto out;
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dev_net_set(dev, net);
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err = register_netdev(dev);
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if (err)
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goto out_free_netdev;
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BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
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net->loopback_dev = dev;
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return 0;
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out_free_netdev:
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free_netdev(dev);
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out:
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if (net_eq(net, &init_net))
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panic("loopback: Failed to register netdevice: %d\n", err);
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return err;
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}
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/* Registered in net/core/dev.c */
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struct pernet_operations __net_initdata loopback_net_ops = {
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.init = loopback_net_init,
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.async = true,
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};
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