/* * snull.c --  the Simple Network Utility * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files.  The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates.   No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * $Id: snull.c,v 1.17 2001/07/18 22:28:18 rubini Exp $ */#ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#include <linux/config.h>#include <linux/module.h>#include <linux/sched.h>#include <linux/kernel.h> /* printk() */#include <linux/malloc.h> /* kmalloc() */#include <linux/errno.h>  /* error codes */#include <linux/types.h>  /* size_t */#include <linux/interrupt.h> /* mark_bh */#include <linux/in.h>#include <linux/netdevice.h>   /* struct device, and other headers */#include <linux/etherdevice.h> /* eth_type_trans */#include <linux/ip.h>          /* struct iphdr */#include <linux/tcp.h>         /* struct tcphdr */#include <linux/skbuff.h>#include "snull.h"#ifdef LINUX_20#  include <linux/if_ether.h>#  define net_device_stats enet_statistics#else#  include <linux/in6.h>#endif#include <asm/checksum.h>MODULE_AUTHOR("Alessandro Rubini");/* This is a load-time options */static int eth = 0; /* Call yourself "ethX". Default is "sn0"/"sn1" */MODULE_PARM(eth, "i");/* * Transmitter lockup simulation, normally disabled. */static int lockup = 0;MODULE_PARM(lockup, "i");#ifdef HAVE_TX_TIMEOUTstatic int timeout = SNULL_TIMEOUT;MODULE_PARM(timeout, "i");#endifint snull_eth;/* * This structure is private to each device. It is used to pass * packets in and out, so there is place for a packet */struct snull_priv {    struct net_device_stats stats;    int status;    int rx_packetlen;    u8 *rx_packetdata;    int tx_packetlen;    u8 *tx_packetdata;    struct sk_buff *skb;    spinlock_t lock;};extern struct net_device snull_devs[];void snull_tx_timeout (struct net_device *dev);        /* * Open and close */int snull_open(struct net_device *dev){    MOD_INC_USE_COUNT;        /* request_region(), request_irq(), ....  (like fops->open) */#if 0 && defined(LINUX_20)    /*     * We have no irq line, otherwise this assignment can be used to     * grab a non-shared interrupt. To share interrupt lines use     * the dev_id argument of request_irq. See snull_interrupt below.     */    irq2dev_map[dev->irq] = dev;#endif    /*      * Assign the hardware address of the board: use "\0SNULx", where     * x is 0 or 1. The first byte is '\0' to avoid being a multicast     * address (the first byte of multicast addrs is odd).     */    memcpy(dev->dev_addr, "\0SNUL0", ETH_ALEN);    dev->dev_addr[ETH_ALEN-1] += (dev - snull_devs); /* the number */#ifndef LINUX_24                    dev->start = 1;             #endif                              netif_start_queue(dev);    return 0;}int snull_release(struct net_device *dev){    /* release ports, irq and such -- like fops->close */    netif_stop_queue(dev); /* can't transmit any more */#ifndef LINUX_24                    dev->start = 0;             #endif                              MOD_DEC_USE_COUNT;    /* if irq2dev_map was used (2.0 kernel), zero the entry here */    return 0;}/* * Configuration changes (passed on by ifconfig) */int snull_config(struct net_device *dev, struct ifmap *map){    if (dev->flags & IFF_UP) /* can't act on a running interface */        return -EBUSY;    /* Don't allow changing the I/O address */    if (map->base_addr != dev->base_addr) {        printk(KERN_WARNING "snull: Can't change I/O address\n");        return -EOPNOTSUPP;    }    /* Allow changing the IRQ */    if (map->irq != dev->irq) {        dev->irq = map->irq;        /* request_irq() is delayed to open-time */    }    /* ignore other fields */    return 0;}/* * Receive a packet: retrieve, encapsulate and pass over to upper levels */void snull_rx(struct net_device *dev, int len, unsigned char *buf){    struct sk_buff *skb;    struct snull_priv *priv = (struct snull_priv *) dev->priv;    /*     * The packet has been retrieved from the transmission     * medium. Build an skb around it, so upper layers can handle it     */    skb = dev_alloc_skb(len+2);    if (!skb) {        printk("snull rx: low on mem - packet dropped\n");        priv->stats.rx_dropped++;        return;    }    skb_reserve(skb, 2); /* align IP on 16B boundary */      memcpy(skb_put(skb, len), buf, len);    /* Write metadata, and then pass to the receive level */    skb->dev = dev;    skb->protocol = eth_type_trans(skb, dev);    skb->ip_summed = CHECKSUM_UNNECESSARY; /* don't check it */    priv->stats.rx_packets++;#ifndef LINUX_20                            priv->stats.rx_bytes += len;#endif                                      netif_rx(skb);    return;}            /* * The typical interrupt entry point */#ifdef LINUX_24void snull_interrupt(int irq, void *dev_id, struct pt_regs *regs){    int statusword;    struct snull_priv *priv;    /*     * As usual, check the "device" pointer for shared handlers.     * Then assign "struct device *dev"     */    struct net_device *dev = (struct net_device *)dev_id;    /* ... and check with hw if it's really ours */    if (!dev /*paranoid*/ ) return;    /* Lock the device */    priv = (struct snull_priv *) dev->priv;    spin_lock(&priv->lock);    /* retrieve statusword: real netdevices use I/O instructions */    statusword = priv->status;    if (statusword & SNULL_RX_INTR) {        /* send it to snull_rx for handling */        snull_rx(dev, priv->rx_packetlen, priv->rx_packetdata);    }    if (statusword & SNULL_TX_INTR) {        /* a transmission is over: free the skb */        priv->stats.tx_packets++;        priv->stats.tx_bytes += priv->tx_packetlen;        dev_kfree_skb(priv->skb);    }    /* Unlock the device and we are done */    spin_unlock(&priv->lock);    return;}#else /* LINUX_22 or earlier */void snull_interrupt(int irq, void *dev_id, struct pt_regs *regs){    int statusword;    struct snull_priv *priv;    /*     * As usual, check the "device" pointer for shared handlers.     * Then assign "struct device *dev"     */#if 0 && defined(LINUX_20)    /* This is the way to do things for non-shared handlers */    struct device *dev = (struct device *)(irq2dev_map[irq]);#else    /* Otherwise use this SA_SHIRQ-safe approach */    struct net_device *dev = (struct net_device *)dev_id;    /* ... and check with hw if it's really ours */#endif    if (!dev /*paranoid*/ ) return;    /* Lock the device */    priv = (struct snull_priv *) dev->priv;    spin_lock(&priv->lock);    dev->interrupt = 1;    /* retrieve statusword: real netdevices use inb() or inw() */    statusword = priv->status;    if (statusword & SNULL_RX_INTR) {        /* send it to snull_rx for handling */        snull_rx(dev, priv->rx_packetlen, priv->rx_packetdata);    }    if (statusword & SNULL_TX_INTR) {        /* a transmission is over: tell we are no more busy */        priv->stats.tx_packets++;#ifndef LINUX_20        priv->stats.tx_bytes += priv->tx_packetlen;#endif        dev_kfree_skb(priv->skb);    }    spin_unlock(&priv->lock);    dev->interrupt = 0;    return;}#endif /* LINUX_22 or earlier *//* * Transmit a packet (low level interface) */void snull_hw_tx(char *buf, int len, struct net_device *dev){    /*     * This function deals with hw details. This interface loops     * back the packet to the other snull interface (if any).     * In other words, this function implements the snull behaviour,     * while all other procedures are rather device-independent     */    struct iphdr *ih;    struct net_device *dest;    struct snull_priv *priv;    u32 *saddr, *daddr;    /* I am paranoid. Ain't I? */    if (len < sizeof(struct ethhdr) + sizeof(struct iphdr)) {        printk("snull: Hmm... packet too short (%i octets)\n",               len);        return;    }    if (0) { /* enable this conditional to look at the data */        int i;        PDEBUG("len is %i\n" KERN_DEBUG "data:",len);        for (i=14 ; i<len; i++)            printk(" %02x",buf[i]&0xff);        printk("\n");    }    /*