drivers/net/loopback.c

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 1 /*
 2  * INET An implementation of the TCP/IP protocol suite for the LINUX
 3  * operating system. INET is implemented using the BSD Socket
 4  * interface as the means of communication with the user level.
 5  *
 6  * Pseudo-driver for the loopback interface.
 7  *
 8  * Version: @(#)loopback.c 1.0.4b 08/16/93
 9  *
 10  * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
 11  * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  * Donald Becker, <becker@cesdis.gsfc.nasa.gov>
 13  *
 14  * Alan Cox : Fixed oddments for NET3.014
 15  * Alan Cox : Rejig for NET3.029 snap #3
 16  * Alan Cox : Fixed NET3.029 bugs and sped up
 17  * Larry McVoy : Tiny tweak to double performance
 18  * Alan Cox : Backed out LMV's tweak - the linux mm
 19  * can't take it...
 20  * Michael Griffith: Don't bother computing the checksums
 21  * on packets received on the loopback
 22  * interface.
 23  * Alexey Kuznetsov: Potential hang under some extreme
 24  * cases removed.
 25  *
 26  * This program is free software; you can redistribute it and/or
 27  * modify it under the terms of the GNU General Public License
 28  * as published by the Free Software Foundation; either version
 29  * 2 of the License, or (at your option) any later version.
 30  */
 31 #include <linux/config.h>
 32 #include <linux/kernel.h>
 33 #include <linux/sched.h>
 34 #include <linux/interrupt.h>
 35 #include <linux/fs.h>
 36 #include <linux/types.h>
 37 #include <linux/string.h>
 38 #include <linux/socket.h>
 39 #include <linux/errno.h>
 40 #include <linux/fcntl.h>
 41 #include <linux/in.h>
 42
 43 #include <asm/system.h>
 44 #include <asm/uaccess.h>
 45 #include <asm/io.h>
 46
 47 #include <linux/inet.h>
 48 #include <linux/netdevice.h>
 49 #include <linux/etherdevice.h>
 50 #include <linux/skbuff.h>
 51 #include <net/sock.h>
 52 #include <linux/if_ether.h>/* For the statistics structure. */
 53 #include <linux/if_arp.h>/* For ARPHRD_ETHER */
 54
 55 #define LOOPBACK_MTU (PAGE_SIZE*7/8)
 56
 57 /*
 58  * The higher levels take care of making this non-reentrant (it's
 59  * called with bh's disabled).
 60  */
 61 static intloopback_xmit(struct sk_buff *skb,struct device *dev)
 62 {
 63 struct enet_statistics *stats = (struct enet_statistics *)dev->priv;
 64
 65 if(skb == NULL || dev == NULL)
 66 return(0);
 67
 68 /*
 69  * Optimise so buffers with skb->free=1 are not copied but
 70  * instead are lobbed from tx queue to rx queue
 71  */
 72
 73 if(skb->users !=1)
 74 {
 75 struct sk_buff *skb2=skb;
 76  skb=skb_clone(skb, GFP_ATOMIC);/* Clone the buffer */
 77 if(skb==NULL) {
 78 kfree_skb(skb2, FREE_WRITE);
 79 return0;
 80 }
 81 kfree_skb(skb2, FREE_WRITE);
 82 }
 83 else
 84 skb_orphan(skb);
 85
 86  skb->protocol=eth_type_trans(skb,dev);
 87  skb->dev=dev;
 88 #ifndef LOOPBACK_MUST_CHECKSUM
 89  skb->ip_summed = CHECKSUM_UNNECESSARY;
 90 #endif
 91 netif_rx(skb);
 92
 93  stats->rx_packets++;
 94  stats->tx_packets++;
 95
 96 return(0);
 97 }
 98
 99 static struct enet_statistics *get_stats(struct device *dev)
 100 {
 101 return(struct enet_statistics *)dev->priv;
 102 }
 103
 104 static intloopback_open(struct device *dev)
 105 {
 106  dev->flags|=IFF_LOOPBACK;
 107 return0;
 108 }
 109
 110 /* Initialize the rest of the LOOPBACK device. */
 111 intloopback_init(struct device *dev)
 112 {
 113 int i;
 114
 115  dev->mtu = LOOPBACK_MTU;
 116  dev->tbusy =0;
 117  dev->hard_start_xmit = loopback_xmit;
 118  dev->hard_header = eth_header;
 119  dev->hard_header_cache = eth_header_cache;
 120  dev->header_cache_update= eth_header_cache_update;
 121  dev->hard_header_len = ETH_HLEN;/* 14 */
 122  dev->addr_len = ETH_ALEN;/* 6 */
 123  dev->tx_queue_len =0;
 124  dev->type = ARPHRD_LOOPBACK;/* 0x0001 */
 125  dev->rebuild_header = eth_rebuild_header;
 126  dev->open = loopback_open;
 127  dev->flags = IFF_LOOPBACK|IFF_BROADCAST;
 128  dev->family = AF_INET;
 129 #ifdef CONFIG_INET
 130  dev->pa_addr =in_aton("127.0.0.1");
 131  dev->pa_brdaddr =in_aton("127.255.255.255");
 132  dev->pa_mask =in_aton("255.0.0.0");
 133  dev->pa_alen =4;
 134 #endif
 135  dev->priv =kmalloc(sizeof(struct enet_statistics), GFP_KERNEL);
 136 if(dev->priv == NULL)
 137 return-ENOMEM;
 138 memset(dev->priv,0,sizeof(struct enet_statistics));
 139  dev->get_stats = get_stats;
 140
 141 /*
 142  * Fill in the generic fields of the device structure.
 143  */
 144
 145 for(i =0; i < DEV_NUMBUFFS; i++)
 146 skb_queue_head_init(&dev->buffs[i]);
 147
 148 return(0);
 149 };