/* * 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@cesdis.gsfc.nasa.gov> * * 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/sched.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 <net/sock.h> #include <linux/if_ether.h> /* For the statistics structure. */ #include <linux/if_arp.h> /* For ARPHRD_ETHER */ #define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16) /* * The higher levels take care of making this non-reentrant (it's * called with bh's disabled). */ 61 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) { struct net_device_stats *stats = (struct net_device_stats *)dev->priv; /* * Optimise so buffers with skb->free=1 are not copied but * instead are lobbed from tx queue to rx queue */ 70 if(atomic_read(&skb->users) != 1) { struct sk_buff *skb2=skb; skb=skb_clone(skb, GFP_ATOMIC); /* Clone the buffer */ 74 if(skb==NULL) { kfree_skb(skb2); 76 return 0; } kfree_skb(skb2); } 80 else skb_orphan(skb); skb->protocol=eth_type_trans(skb,dev); skb->dev=dev; #ifndef LOOPBACK_MUST_CHECKSUM skb->ip_summed = CHECKSUM_UNNECESSARY; #endif netif_rx(skb); stats->rx_bytes+=skb->len; stats->tx_bytes+=skb->len; stats->rx_packets++; stats->tx_packets++; 95 return(0); } 98 static struct net_device_stats *get_stats(struct net_device *dev) { 100 return (struct net_device_stats *)dev->priv; } /* Initialize the rest of the LOOPBACK device. */ 104 int __init loopback_init(struct net_device *dev) { dev->mtu = PAGE_SIZE - LOOPBACK_OVERHEAD; dev->hard_start_xmit = loopback_xmit; dev->hard_header = eth_header; dev->hard_header_cache = eth_header_cache; dev->header_cache_update= eth_header_cache_update; dev->hard_header_len = ETH_HLEN; /* 14 */ dev->addr_len = ETH_ALEN; /* 6 */ dev->tx_queue_len = 0; dev->type = ARPHRD_LOOPBACK; /* 0x0001 */ dev->rebuild_header = eth_rebuild_header; dev->flags = IFF_LOOPBACK; dev->priv = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL); 118 if (dev->priv == NULL) 119 return -ENOMEM; memset(dev->priv, 0, sizeof(struct net_device_stats)); dev->get_stats = get_stats; 123 if (num_physpages >= ((128*1024*1024)>>PAGE_SHIFT)) dev->mtu = 4096*4 - LOOPBACK_OVERHEAD; /* * Fill in the generic fields of the device structure. */ dev_init_buffers(dev); 132 return(0); };