1 files changed, 233 insertions, 0 deletions

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
new file mode 100644
index 000000000000..2ffc31708d5f
--- /dev/null
+++ b/drivers/net/loopback.c
@@ -0,0 +1,233 @@
+/*
+ * 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, <bir7@leland.Stanford.Edu>
+ *              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>
+
+static DEFINE_PER_CPU(struct net_device_stats, loopback_stats);
+
+#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.
+ */
+
+static void emulate_large_send_offload(struct sk_buff *skb)
+{
+        struct iphdr *iph = skb->nh.iph;
+        struct tcphdr *th = (struct tcphdr*)(skb->nh.raw + (iph->ihl * 4));
+        unsigned int doffset = (iph->ihl + th->doff) * 4;
+        unsigned int mtu = skb_shinfo(skb)->tso_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);
+                nskb->mac.raw = nskb->data - 14;
+                nskb->nh.raw = nskb->data;
+                iph = nskb->nh.iph;
+                memcpy(nskb->data, skb->nh.raw, 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*)(nskb->nh.raw + 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);
+}
+
+/*
+ * 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 net_device_stats *lb_stats;
+
+        skb_orphan(skb);
+
+        skb->protocol=eth_type_trans(skb,dev);
+        skb->dev=dev;
+#ifndef LOOPBACK_MUST_CHECKSUM
+        skb->ip_summed = CHECKSUM_UNNECESSARY;
+#endif
+
+        if (skb_shinfo(skb)->tso_size) {
+                BUG_ON(skb->protocol != htons(ETH_P_IP));
+                BUG_ON(skb->nh.iph->protocol != IPPROTO_TCP);
+
+                emulate_large_send_offload(skb);
+                return 0;
+        }
+
+        dev->last_rx = jiffies;
+
+        lb_stats = &per_cpu(loopback_stats, get_cpu());
+        lb_stats->rx_bytes += skb->len;
+        lb_stats->tx_bytes += skb->len;
+        lb_stats->rx_packets++;
+        lb_stats->tx_packets++;
+        put_cpu();
+
+        netif_rx(skb);
+
+        return(0);
+}
+
+static struct net_device_stats *get_stats(struct net_device *dev)
+{
+        struct net_device_stats *stats = dev->priv;
+        int i;
+
+        if (!stats) {
+                return NULL;
+        }
+
+        memset(stats, 0, sizeof(struct net_device_stats));
+
+        for (i=0; i < NR_CPUS; i++) {
+                struct net_device_stats *lb_stats;
+
+                if (!cpu_possible(i)) 
+                        continue;
+                lb_stats = &per_cpu(loopback_stats, i);
+                stats->rx_bytes   += lb_stats->rx_bytes;
+                stats->tx_bytes   += lb_stats->tx_bytes;
+                stats->rx_packets += lb_stats->rx_packets;
+                stats->tx_packets += lb_stats->tx_packets;
+        }
+                                
+        return stats;
+}
+
+static u32 loopback_get_link(struct net_device *dev)
+{
+        return 1;
+}
+
+static struct ethtool_ops loopback_ethtool_ops = {
+        .get_link               = loopback_get_link,
+        .get_tso                = ethtool_op_get_tso,
+        .set_tso                = ethtool_op_set_tso,
+};
+
+struct net_device loopback_dev = {
+        .name                   = "lo",
+        .mtu                    = (16 * 1024) + 20 + 20 + 12,
+        .hard_start_xmit        = loopback_xmit,
+        .hard_header            = eth_header,
+        .hard_header_cache      = eth_header_cache,
+        .header_cache_update    = eth_header_cache_update,
+        .hard_header_len        = ETH_HLEN,     /* 14   */
+        .addr_len               = ETH_ALEN,     /* 6    */
+        .tx_queue_len           = 0,
+        .type                   = ARPHRD_LOOPBACK,      /* 0x0001*/
+        .rebuild_header         = eth_rebuild_header,
+        .flags                  = IFF_LOOPBACK,
+        .features               = NETIF_F_SG|NETIF_F_FRAGLIST
+                                  |NETIF_F_NO_CSUM|NETIF_F_HIGHDMA
+                                  |NETIF_F_LLTX,
+        .ethtool_ops            = &loopback_ethtool_ops,
+};
+
+/* Setup and register the of the LOOPBACK device. */
+int __init loopback_init(void)
+{
+        struct net_device_stats *stats;
+
+        /* Can survive without statistics */
+        stats = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
+        if (stats) {
+                memset(stats, 0, sizeof(struct net_device_stats));
+                loopback_dev.priv = stats;
+                loopback_dev.get_stats = &get_stats;
+        }
+        
+        return register_netdev(&loopback_dev);
+};
+
+EXPORT_SYMBOL(loopback_dev);