eth.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

/*
 * 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.
 *
 *		Ethernet-type device handling.
 *
 * Version:	@(#)eth.c	1.0.7	05/25/93
 *
 * Authors:	Ross Biro, <[e-mail]>
 *		Fred N. van Kempen, <[e-mail]>
 *		Mark Evans, <[e-mail]>
 * 
 * Fixes:
 *		Mr Linux	: Arp problems
 *		Alan Cox	: Generic queue tidyup (very tiny here)
 *		Alan Cox	: eth_header ntohs should be htons
 *		Alan Cox	: eth_rebuild_header missing an htons and
 *				  minor other things.
 *		Tegge		: Arp bug fixes. 
 *
 *		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 <asm/segment.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/in.h>
#include "inet.h"
#include "dev.h"
#include "eth.h"
#include "ip.h"
#include "route.h"
#include "protocol.h"
#include "tcp.h"
#include "skbuff.h"
#include "sock.h"
#include <linux/errno.h>
#include "arp.h"


/* Display an Ethernet address in readable format. */
char *eth_print(unsigned char *ptr)
{
  static char buff[64];

  if (ptr == NULL) return("[NONE]");
  sprintf(buff, "%02X:%02X:%02X:%02X:%02X:%02X",
	(ptr[0] & 255), (ptr[1] & 255), (ptr[2] & 255),
	(ptr[3] & 255), (ptr[4] & 255), (ptr[5] & 255)
  );
  return(buff);
}

void eth_setup(char *str, int *ints)
{
	struct device *d = dev_base;

	if (!str || !*str)
		return;
	while (d) {
		if (!strcmp(str,d->name)) {
			if (ints[0] > 0)
				d->irq=ints[1];
			if (ints[0] > 1)
				d->base_addr=ints[2];
			if (ints[0] > 2)
				d->mem_start=ints[3];
			if (ints[0] > 3)
				d->mem_end=ints[4];
			break;
		}
		d=d->next;
	}
}

/* Display the contents of the Ethernet MAC header. */
void
eth_dump(struct ethhdr *eth)
{
  if (inet_debug != DBG_ETH) return;

  printk("eth: SRC = %s ", eth_print(eth->h_source));
  printk("DST = %s ", eth_print(eth->h_dest));
  printk("TYPE = %04X\n", ntohs(eth->h_proto));
}


/* Create the Ethernet MAC header. */
int
eth_header(unsigned char *buff, struct device *dev, unsigned short type,
	   unsigned long daddr, unsigned long saddr, unsigned len)
{
  struct ethhdr *eth;

  DPRINTF((DBG_DEV, "ETH: header(%s, ", in_ntoa(saddr)));
  DPRINTF((DBG_DEV, "%s, 0x%X)\n", in_ntoa(daddr), type));

  /* Fill in the basic Ethernet MAC header. */
  eth = (struct ethhdr *) buff;
  eth->h_proto = htons(type);

  /* We don't ARP for the LOOPBACK device... */
  if (dev->flags & IFF_LOOPBACK) {
	DPRINTF((DBG_DEV, "ETH: No header for loopback\n"));
	memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
	memset(eth->h_dest, 0, dev->addr_len);
	return(dev->hard_header_len);
  }

  /* Check if we can use the MAC BROADCAST address. */
  if (chk_addr(daddr) == IS_BROADCAST) {
	DPRINTF((DBG_DEV, "ETH: Using MAC Broadcast\n"));
	memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
	memcpy(eth->h_dest, dev->broadcast, dev->addr_len);
	return(dev->hard_header_len);
  }
  cli();
  memcpy(eth->h_source, &saddr, 4);
  /* No. Ask ARP to resolve the Ethernet address. */
  if (arp_find(eth->h_dest, daddr, dev, dev->pa_addr)) 
  {
        sti();
        if(type!=ETH_P_IP)
        	printk("Erk: protocol %X got into an arp request state!\n",type);
	return(-dev->hard_header_len);
  } 
  else
  {
  	memcpy(eth->h_source,dev->dev_addr,dev->addr_len);	/* This was missing causing chaos if the
  								   header built correctly! */
  	sti();
  	return(dev->hard_header_len);
  }
}


/* Rebuild the Ethernet MAC header. */
int
eth_rebuild_header(void *buff, struct device *dev)
{
  struct ethhdr *eth;
  unsigned long src, dst;

  DPRINTF((DBG_DEV, "ETH: Using MAC Broadcast\n"));
  eth = (struct ethhdr *) buff;
  src = *(unsigned long *) eth->h_source;
  dst = *(unsigned long *) eth->h_dest;
  DPRINTF((DBG_DEV, "ETH: RebuildHeader: SRC=%s ", in_ntoa(src)));
  DPRINTF((DBG_DEV, "DST=%s\n", in_ntoa(dst)));
  if(eth->h_proto!=htons(ETH_P_ARP))	/* This ntohs kind of helps a bit! */
	  if (arp_find(eth->h_dest, dst, dev, dev->pa_addr /* src */)) return(1);
  memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
  return(0);
}


/* Add an ARP entry for a host on this interface. */
void
eth_add_arp(unsigned long addr, struct sk_buff *skb, struct device *dev)
{
  struct ethhdr *eth;

  eth = (struct ethhdr *) skb->data;
  arp_add(addr, eth->h_source, dev);
}


/* Determine the packet's protocol ID. */
unsigned short
eth_type_trans(struct sk_buff *skb, struct device *dev)
{
  struct ethhdr *eth;

  eth = (struct ethhdr *) skb->data;

  if(ntohs(eth->h_proto)<1536)
  	return(htons(ETH_P_802_3));
  return(eth->h_proto);
}