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/*

 * INET         An implementation of the TCP/IP protocol suite for the LINUX

 *              operating system.  INET is implemented using the  BSD Socket

 *              interface as the means of communication with the user level.

 *

 *              Pseudo-driver for the loopback interface.

 *

 * Version:     @(#)loopback.c  1.0.4b  08/16/93

 *

 * Authors:     Ross Biro

 *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>

 *              Donald Becker, <becker@scyld.com>

 *

 *              Alan Cox        :       Fixed oddments for NET3.014

 *              Alan Cox        :       Rejig for NET3.029 snap #3

 *              Alan Cox        :       Fixed NET3.029 bugs and sped up

 *              Larry McVoy     :       Tiny tweak to double performance

 *              Alan Cox        :       Backed out LMV's tweak - the linux mm

 *                                      can't take it...

 *              Michael Griffith:       Don't bother computing the checksums

 *                                      on packets received on the loopback

 *                                      interface.

 *              Alexey Kuznetsov:       Potential hang under some extreme

 *                                      cases removed.

 *

 *              This program is free software; you can redistribute it and/or

 *              modify it under the terms of the GNU General Public License

 *              as published by the Free Software Foundation; either version

 *              2 of the License, or (at your option) any later version.

 */

#include <linux/kernel.h>

#include <linux/jiffies.h>

#include <linux/module.h>

#include <linux/interrupt.h>

#include <linux/fs.h>

#include <linux/types.h>

#include <linux/string.h>

#include <linux/socket.h>

#include <linux/errno.h>

#include <linux/fcntl.h>

#include <linux/in.h>

#include <linux/init.h>

#include <asm/system.h>

#include <asm/uaccess.h>

#include <asm/io.h>

#include <linux/inet.h>

#include <linux/netdevice.h>

#include <linux/etherdevice.h>

#include <linux/skbuff.h>

#include <linux/ethtool.h>

#include <net/sock.h>

#include <net/checksum.h>

#include <linux/if_ether.h>     /* For the statistics structure. */

#include <linux/if_arp.h>       /* For ARPHRD_ETHER */

#include <linux/ip.h>

#include <linux/tcp.h>

#include <linux/percpu.h>

#include <net/net_namespace.h>

struct pcpu_lstats {

        unsigned long packets;

        unsigned long bytes;

};

#define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)

/* KISS: just allocate small chunks and copy bits.

 *

 * So, in fact, this is documentation, explaining what we expect

 * of largesending device modulo TCP checksum, which is ignored for loopback.

 */

#ifdef LOOPBACK_TSO

static void emulate_large_send_offload(struct sk_buff *skb)

{

        struct iphdr *iph = ip_hdr(skb);

        struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) +

                                              (iph->ihl * 4));

        unsigned int doffset = (iph->ihl + th->doff) * 4;

        unsigned int mtu = skb_shinfo(skb)->gso_size + doffset;

        unsigned int offset = 0;

        u32 seq = ntohl(th->seq);

        u16 id  = ntohs(iph->id);

        while (offset + doffset < skb->len) {

                unsigned int frag_size = min(mtu, skb->len - offset) - doffset;

                struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC);

                if (!nskb)

                        break;

                skb_reserve(nskb, 32);

                skb_set_mac_header(nskb, -ETH_HLEN);

                skb_reset_network_header(nskb);

                iph = ip_hdr(nskb);

                skb_copy_to_linear_data(nskb, skb_network_header(skb),

                                        doffset);

                if (skb_copy_bits(skb,

                                  doffset + offset,

                                  nskb->data + doffset,

                                  frag_size))

                        BUG();

                skb_put(nskb, doffset + frag_size);

                nskb->ip_summed = CHECKSUM_UNNECESSARY;

                nskb->dev = skb->dev;

                nskb->priority = skb->priority;

                nskb->protocol = skb->protocol;

                nskb->dst = dst_clone(skb->dst);

                memcpy(nskb->cb, skb->cb, sizeof(skb->cb));

                nskb->pkt_type = skb->pkt_type;

                th = (struct tcphdr *)(skb_network_header(nskb) + iph->ihl * 4);

                iph->tot_len = htons(frag_size + doffset);

                iph->id = htons(id);

                iph->check = 0;

                iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl);

                th->seq = htonl(seq);

                if (offset + doffset + frag_size < skb->len)

                        th->fin = th->psh = 0;

                netif_rx(nskb);

                offset += frag_size;

                seq += frag_size;

                id++;

        }

        dev_kfree_skb(skb);

}

#endif /* LOOPBACK_TSO */

/*

 * The higher levels take care of making this non-reentrant (it's

 * called with bh's disabled).

 */

static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)

{

        struct pcpu_lstats *pcpu_lstats, *lb_stats;

        skb_orphan(skb);

        skb->protocol = eth_type_trans(skb,dev);

#ifndef LOOPBACK_MUST_CHECKSUM

        skb->ip_summed = CHECKSUM_UNNECESSARY;

#endif

#ifdef LOOPBACK_TSO

        if (skb_is_gso(skb)) {

                BUG_ON(skb->protocol != htons(ETH_P_IP));

                BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP);

                emulate_large_send_offload(skb);

                return 0;

        }

#endif

        dev->last_rx = jiffies;

        /* it's OK to use per_cpu_ptr() because BHs are off */

        pcpu_lstats = netdev_priv(dev);

        lb_stats = per_cpu_ptr(pcpu_lstats, smp_processor_id());

        lb_stats->bytes += skb->len;

        lb_stats->packets++;

        netif_rx(skb);

        return 0;

}

static struct net_device_stats *get_stats(struct net_device *dev)

{

        const struct pcpu_lstats *pcpu_lstats;

        struct net_device_stats *stats = &dev->stats;

        unsigned long bytes = 0;

        unsigned long packets = 0;

        int i;

        pcpu_lstats = netdev_priv(dev);

        for_each_possible_cpu(i) {

                const struct pcpu_lstats *lb_stats;

                lb_stats = per_cpu_ptr(pcpu_lstats, i);

                bytes   += lb_stats->bytes;

                packets += lb_stats->packets;

        }

        stats->rx_packets = packets;

        stats->tx_packets = packets;

        stats->rx_bytes = bytes;

        stats->tx_bytes = bytes;

        return stats;

}

static u32 always_on(struct net_device *dev)

{

        return 1;

}

static const struct ethtool_ops loopback_ethtool_ops = {

        .get_link               = always_on,

        .set_tso                = ethtool_op_set_tso,

        .get_tx_csum            = always_on,

        .get_sg                 = always_on,

        .get_rx_csum            = always_on,

};

static int loopback_dev_init(struct net_device *dev)

{

        struct pcpu_lstats *lstats;

        lstats = alloc_percpu(struct pcpu_lstats);

        if (!lstats)

                return -ENOMEM;

        dev->priv = lstats;

        return 0;

}

static void loopback_dev_free(struct net_device *dev)

{

        struct pcpu_lstats *lstats = netdev_priv(dev);

        free_percpu(lstats);

        free_netdev(dev);

}

/*

 * The loopback device is special. There is only one instance

 * per network namespace.

 */

static void loopback_setup(struct net_device *dev)

{

        dev->get_stats          = &get_stats;

        dev->mtu                = (16 * 1024) + 20 + 20 + 12;

        dev->hard_start_xmit    = loopback_xmit;

        dev->hard_header_len    = ETH_HLEN;     /* 14   */

        dev->addr_len           = ETH_ALEN;     /* 6    */

        dev->tx_queue_len       = 0;

        dev->type               = ARPHRD_LOOPBACK;      /* 0x0001*/

        dev->flags              = IFF_LOOPBACK;

        dev->features           = NETIF_F_SG | NETIF_F_FRAGLIST

#ifdef LOOPBACK_TSO

                | NETIF_F_TSO

#endif

                | NETIF_F_NO_CSUM

                | NETIF_F_HIGHDMA

                | NETIF_F_LLTX

                | NETIF_F_NETNS_LOCAL;

        dev->ethtool_ops        = &loopback_ethtool_ops;

        dev->header_ops         = &eth_header_ops;

        dev->init = loopback_dev_init;

        dev->destructor = loopback_dev_free;

}

/* Setup and register the loopback device. */

static __net_init int loopback_net_init(struct net *net)

{

        struct net_device *dev;

        int err;

        err = -ENOMEM;

        dev = alloc_netdev(0, "lo", loopback_setup);

        if (!dev)

                goto out;

        dev->nd_net = net;

        err = register_netdev(dev);

        if (err)

                goto out_free_netdev;

        net->loopback_dev = dev;

        return 0;

out_free_netdev:

        free_netdev(dev);

out:

        if (net == &init_net)

                panic("loopback: Failed to register netdevice: %d\n", err);

        return err;

}

static __net_exit void loopback_net_exit(struct net *net)

{

        struct net_device *dev = net->loopback_dev;

        unregister_netdev(dev);

}

static struct pernet_operations __net_initdata loopback_net_ops = {

       .init = loopback_net_init,

       .exit = loopback_net_exit,

};

static int __init loopback_init(void)

{

        return register_pernet_device(&loopback_net_ops);

}

/* Loopback is special. It should be initialized before any other network

 * device and network subsystem.

 */

fs_initcall(loopback_init);