icmp.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.
 *
 *		Internet Control Message Protocol (ICMP)
 *
 * Version:	@(#)icmp.c	1.0.11	06/02/93
 *
 * Authors:	Ross Biro, <[e-mail]>
 *		Fred N. van Kempen, <[e-mail]>
 *		Mark Evans, <[e-mail]>
 *
 * Fixes:	
 *		Alan Cox	:	Generic queue usage.
 *		Gerhard Koerting:	ICMP addressing corrected
 *		Alan Cox	:	Use tos/ttl settings
 *
 *
 *		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/types.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include "inet.h"
#include "dev.h"
#include "ip.h"
#include "route.h"
#include "protocol.h"
#include "icmp.h"
#include "tcp.h"
#include "skbuff.h"
#include "sock.h"
#include <linux/errno.h>
#include <linux/timer.h>
#include <asm/system.h>
#include <asm/segment.h>


#define min(a,b)	((a)<(b)?(a):(b))


/* An array of errno for error messages from dest unreach. */
struct icmp_err icmp_err_convert[] = {
  { ENETUNREACH,	1 },	/*	ICMP_NET_UNREACH	*/
  { EHOSTUNREACH,	1 },	/*	ICMP_HOST_UNREACH	*/
  { ENOPROTOOPT,	1 },	/*	ICMP_PROT_UNREACH	*/
  { ECONNREFUSED,	1 },	/*	ICMP_PORT_UNREACH	*/
  { EOPNOTSUPP,		0 },	/*	ICMP_FRAG_NEEDED	*/
  { EOPNOTSUPP,		0 },	/*	ICMP_SR_FAILED		*/
  { ENETUNREACH,	1 },	/* 	ICMP_NET_UNKNOWN	*/
  { EHOSTDOWN,		1 },	/*	ICMP_HOST_UNKNOWN	*/
  { ENONET,		1 },	/*	ICMP_HOST_ISOLATED	*/
  { ENETUNREACH,	1 },	/*	ICMP_NET_ANO		*/
  { EHOSTUNREACH,	1 },	/*	ICMP_HOST_ANO		*/
  { EOPNOTSUPP,		0 },	/*	ICMP_NET_UNR_TOS	*/
  { EOPNOTSUPP,		0 }	/*	ICMP_HOST_UNR_TOS	*/
};


/* Display the contents of an ICMP header. */
static void
print_icmp(struct icmphdr *icmph)
{
  if (inet_debug != DBG_ICMP) return;

  printk("ICMP: type = %d, code = %d, checksum = %X\n",
			icmph->type, icmph->code, icmph->checksum);
  printk("      gateway = %s\n", in_ntoa(icmph->un.gateway));
}


/* Send an ICMP message. */
void
icmp_send(struct sk_buff *skb_in, int type, int code, struct device *dev)
{
  struct sk_buff *skb;
  struct iphdr *iph;
  int offset;
  struct icmphdr *icmph;
  int len;

  DPRINTF((DBG_ICMP, "icmp_send(skb_in = %X, type = %d, code = %d, dev=%X)\n",
	   					skb_in, type, code, dev));

  /* Get some memory for the reply. */
  len = sizeof(struct sk_buff) + dev->hard_header_len +
	sizeof(struct iphdr) + sizeof(struct icmphdr) +
	sizeof(struct iphdr) + 8;	/* amount of header to return */
	   
  skb = (struct sk_buff *) alloc_skb(len, GFP_ATOMIC);
  if (skb == NULL) 
  	return;

  skb->sk = NULL;
  skb->mem_addr = skb;
  skb->mem_len = len;
  len -= sizeof(struct sk_buff);

  /* Find the IP header. */
  iph = (struct iphdr *) (skb_in->data + dev->hard_header_len);

  /* Build Layer 2-3 headers for message back to source. */
  offset = ip_build_header(skb, dev->pa_addr, iph->saddr,
			   &dev, IPPROTO_ICMP, NULL, len, skb_in->ip_hdr->tos,255);
  if (offset < 0) {
	skb->sk = NULL;
	kfree_skb(skb, FREE_READ);
	return;
  }

  /* Re-adjust length according to actual IP header size. */
  skb->len = offset + sizeof(struct icmphdr) + sizeof(struct iphdr) + 8;
  icmph = (struct icmphdr *) (skb->data + offset);
  icmph->type = type;
  icmph->code = code;
  icmph->checksum = 0;
  icmph->un.gateway = 0;
  memcpy(icmph + 1, iph, sizeof(struct iphdr) + 8);

  icmph->checksum = ip_compute_csum((unsigned char *)icmph,
                         sizeof(struct icmphdr) + sizeof(struct iphdr) + 8);

  DPRINTF((DBG_ICMP, ">>\n"));
  print_icmp(icmph);

  /* Send it and free it. */
  ip_queue_xmit(NULL, dev, skb, 1);
}


/* Handle ICMP_UNREACH and ICMP_QUENCH. */
static void
icmp_unreach(struct icmphdr *icmph, struct sk_buff *skb)
{
  struct inet_protocol *ipprot;
  struct iphdr *iph;
  unsigned char hash;
  int err;

  err = (icmph->type << 8) | icmph->code;
  iph = (struct iphdr *) (icmph + 1);
  switch(icmph->code & 7) {
	case ICMP_NET_UNREACH:
		DPRINTF((DBG_ICMP, "ICMP: %s: network unreachable.\n",
							in_ntoa(iph->daddr)));
		break;
	case ICMP_HOST_UNREACH:
		DPRINTF((DBG_ICMP, "ICMP: %s: host unreachable.\n",
						in_ntoa(iph->daddr)));
		break;
	case ICMP_PROT_UNREACH:
		printk("ICMP: %s:%d: protocol unreachable.\n",
			in_ntoa(iph->daddr), ntohs(iph->protocol));
		break;
	case ICMP_PORT_UNREACH:
		DPRINTF((DBG_ICMP, "ICMP: %s:%d: port unreachable.\n",
			in_ntoa(iph->daddr), -1 /* FIXME: ntohs(iph->port) */));
		break;
	case ICMP_FRAG_NEEDED:
		printk("ICMP: %s: fragmentation needed and DF set.\n",
							in_ntoa(iph->daddr));
		break;
	case ICMP_SR_FAILED:
		printk("ICMP: %s: Source Route Failed.\n", in_ntoa(iph->daddr));
		break;
	default:
		DPRINTF((DBG_ICMP, "ICMP: Unreachable: CODE=%d from %s\n",
		    		(icmph->code & 7), in_ntoa(iph->daddr)));
		break;
  }

  /* Get the protocol(s). */
  hash = iph->protocol & (MAX_INET_PROTOS -1);

  /* This can change while we are doing it. */
  ipprot = (struct inet_protocol *) inet_protos[hash];
  while(ipprot != NULL) {
	struct inet_protocol *nextip;

	nextip = (struct inet_protocol *) ipprot->next;

	/* Pass it off to everyone who wants it. */
	if (iph->protocol == ipprot->protocol && ipprot->err_handler) {
		ipprot->err_handler(err, (unsigned char *)(icmph + 1),
				    iph->daddr, iph->saddr, ipprot);
	}

	ipprot = nextip;
  }
  skb->sk = NULL;
  kfree_skb(skb, FREE_READ);
}


/* Handle ICMP_REDIRECT. */
static void
icmp_redirect(struct icmphdr *icmph, struct sk_buff *skb, struct device *dev)
{
  struct iphdr *iph;
  unsigned long ip;

  iph = (struct iphdr *) (icmph + 1);
  ip = iph->daddr;
  switch(icmph->code & 7) {
	case ICMP_REDIR_NET:
#ifdef not_a_good_idea
		rt_add((RTF_DYNAMIC | RTF_MODIFIED | RTF_GATEWAY),
			ip, 0, icmph->un.gateway, dev);
		break;
#endif
	case ICMP_REDIR_HOST:
		rt_add((RTF_DYNAMIC | RTF_MODIFIED | RTF_HOST | RTF_GATEWAY),
			ip, 0, icmph->un.gateway, dev);
		break;
	case ICMP_REDIR_NETTOS:
	case ICMP_REDIR_HOSTTOS:
		printk("ICMP: cannot handle TOS redirects yet!\n");
		break;
	default:
		DPRINTF((DBG_ICMP, "ICMP: Unreach: CODE=%d\n",
						(icmph->code & 7)));
		break;
  }
  skb->sk = NULL;
  kfree_skb(skb, FREE_READ);
}


/* Handle ICMP_ECHO ("ping") requests. */
static void
icmp_echo(struct icmphdr *icmph, struct sk_buff *skb, struct device *dev,
	  unsigned long saddr, unsigned long daddr, int len,
	  struct options *opt)
{
  struct icmphdr *icmphr;
  struct sk_buff *skb2;
  int size, offset;

  size = sizeof(struct sk_buff) + dev->hard_header_len + 64 + len;
  skb2 = alloc_skb(size, GFP_ATOMIC);
  if (skb2 == NULL) {
	skb->sk = NULL;
	kfree_skb(skb, FREE_READ);
	return;
  }
  skb2->sk = NULL;
  skb2->mem_addr = skb2;
  skb2->mem_len = size;
  skb2->free = 1;

  /* Build Layer 2-3 headers for message back to source */
  offset = ip_build_header(skb2, daddr, saddr, &dev,
			 	IPPROTO_ICMP, opt, len, skb->ip_hdr->tos,255);
  if (offset < 0) {
	printk("ICMP: Could not build IP Header for ICMP ECHO Response\n");
	kfree_skb(skb2,FREE_WRITE);
	skb->sk = NULL;
	kfree_skb(skb, FREE_READ);
	return;
  }

  /* Re-adjust length according to actual IP header size. */
  skb2->len = offset + len;

  /* Build ICMP_ECHO Response message. */
  icmphr = (struct icmphdr *) (skb2->data + offset);
  memcpy((char *) icmphr, (char *) icmph, len);
  icmphr->type = ICMP_ECHOREPLY;
  icmphr->code = 0;
  icmphr->checksum = 0;
  icmphr->checksum = ip_compute_csum((unsigned char *)icmphr, len);

  /* Ship it out - free it when done */
  ip_queue_xmit((struct sock *)NULL, dev, skb2, 1);

  skb->sk = NULL;
  kfree_skb(skb, FREE_READ);
}


/* Handle the ICMP INFORMATION REQUEST. */
static void
icmp_info(struct icmphdr *icmph, struct sk_buff *skb, struct device *dev,
	  unsigned long saddr, unsigned long daddr, int len,
	  struct options *opt)
{
  /* NOT YET */
  skb->sk = NULL;
  kfree_skb(skb, FREE_READ);
}


/* Handle ICMP_ADRESS_MASK requests. */
static void
icmp_address(struct icmphdr *icmph, struct sk_buff *skb, struct device *dev,
	  unsigned long saddr, unsigned long daddr, int len,
	  struct options *opt)
{
  struct icmphdr *icmphr;
  struct sk_buff *skb2;
  int size, offset;

  size = sizeof(struct sk_buff) + dev->hard_header_len + 64 + len;
  skb2 = alloc_skb(size, GFP_ATOMIC);
  if (skb2 == NULL) {
	skb->sk = NULL;
	kfree_skb(skb, FREE_READ);
	return;
  }
  skb2->sk = NULL;
  skb2->mem_addr = skb2;
  skb2->mem_len = size;
  skb2->free = 1;

  /* Build Layer 2-3 headers for message back to source */
  offset = ip_build_header(skb2, daddr, saddr, &dev,
			 	IPPROTO_ICMP, opt, len, skb->ip_hdr->tos,255);
  if (offset < 0) {
	printk("ICMP: Could not build IP Header for ICMP ADDRESS Response\n");
	kfree_skb(skb2,FREE_WRITE);
	skb->sk = NULL;
	kfree_skb(skb, FREE_READ);
	return;
  }

  /* Re-adjust length according to actual IP header size. */
  skb2->len = offset + len;

  /* Build ICMP ADDRESS MASK Response message. */
  icmphr = (struct icmphdr *) (skb2->data + offset);
  icmphr->type = ICMP_ADDRESSREPLY;
  icmphr->code = 0;
  icmphr->checksum = 0;
  icmphr->un.echo.id = icmph->un.echo.id;
  icmphr->un.echo.sequence = icmph->un.echo.sequence;
  memcpy((char *) (icmphr + 1), (char *) &dev->pa_mask, sizeof(dev->pa_mask));

  icmphr->checksum = ip_compute_csum((unsigned char *)icmphr, len);

  /* Ship it out - free it when done */
  ip_queue_xmit((struct sock *)NULL, dev, skb2, 1);

  skb->sk = NULL;
  kfree_skb(skb, FREE_READ);
}


/* Deal with incoming ICMP packets. */
int
icmp_rcv(struct sk_buff *skb1, struct device *dev, struct options *opt,
	 unsigned long daddr, unsigned short len,
	 unsigned long saddr, int redo, struct inet_protocol *protocol)
{
  struct icmphdr *icmph;
  unsigned char *buff;

  /* Drop broadcast packets. */
  if (chk_addr(daddr) == IS_BROADCAST) {
	DPRINTF((DBG_ICMP, "ICMP: Discarded broadcast from %s\n",
							in_ntoa(saddr)));
	skb1->sk = NULL;
	kfree_skb(skb1, FREE_READ);
	return(0);
  }

  buff = skb1->h.raw;
  icmph = (struct icmphdr *) buff;

  /* Validate the packet first */
  if (ip_compute_csum((unsigned char *) icmph, len)) {
	/* Failed checksum! */
	printk("ICMP: failed checksum from %s!\n", in_ntoa(saddr));
	skb1->sk = NULL;
	kfree_skb(skb1, FREE_READ);
	return(0);
  }
  print_icmp(icmph);

  /* Parse the ICMP message */
  switch(icmph->type) {
	case ICMP_TIME_EXCEEDED:
	case ICMP_DEST_UNREACH:
	case ICMP_SOURCE_QUENCH:
		icmp_unreach(icmph, skb1);
		return(0);
	case ICMP_REDIRECT:
		icmp_redirect(icmph, skb1, dev);
		return(0);
	case ICMP_ECHO: 
		icmp_echo(icmph, skb1, dev, saddr, daddr, len, opt);
		return 0;
	case ICMP_ECHOREPLY:
		skb1->sk = NULL;
		kfree_skb(skb1, FREE_READ);
		return(0);
	case ICMP_INFO_REQUEST:
		icmp_info(icmph, skb1, dev, saddr, daddr, len, opt);
		return 0;
	case ICMP_INFO_REPLY:
		skb1->sk = NULL;
		kfree_skb(skb1, FREE_READ);
		return(0);
	case ICMP_ADDRESS:
		icmp_address(icmph, skb1, dev, saddr, daddr, len, opt);
		return 0;
	case ICMP_ADDRESSREPLY:
		skb1->sk = NULL;
		kfree_skb(skb1, FREE_READ);
		return(0);
	default:
		DPRINTF((DBG_ICMP,
			"ICMP: Unsupported ICMP from %s, type = 0x%X\n",
						in_ntoa(saddr), icmph->type));
		skb1->sk = NULL;
		kfree_skb(skb1, FREE_READ);
		return(0);
  }
  /*NOTREACHED*/
  skb1->sk = NULL;
  kfree_skb(skb1, FREE_READ);
  return(-1);
}


/* Perform any ICMP-related I/O control requests. */
int
icmp_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
  switch(cmd) {
	case DDIOCSDBG:
		return(dbg_ioctl((void *) arg, DBG_ICMP));
	default:
		return(-EINVAL);
  }
  return(0);
}