interface.c

MC Linux/Unix 终端下文件管理器

/* 
   Unix SMB/Netbios implementation.
   Version 1.9.
   multiple interface handling
   Copyright (C) Andrew Tridgell 1992-1998
   
   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.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

extern int DEBUGLEVEL;

struct in_addr ipzero;
struct in_addr allones_ip;
struct in_addr loopback_ip;
static struct in_addr default_ip;
static struct in_addr default_bcast;
static struct in_addr default_nmask;
static BOOL got_ip=False;
static BOOL got_bcast=False;
static BOOL got_nmask=False;

static struct interface *local_interfaces  = NULL;

struct interface *last_iface;

#define ALLONES  ((uint32)0xFFFFFFFF)
#define MKBCADDR(_IP, _NM) ((_IP & _NM) | (_NM ^ ALLONES))
/****************************************************************************
calculate the default netmask for an address
****************************************************************************/
static void default_netmask(struct in_addr *inm, struct in_addr *iad)
{
	/*
	** Guess a netmask based on the class of the IP address given.
	*/
	switch((ntohl(iad->s_addr) & 0xE0000000)) {
        case 0x00000000:     /* Class A addr */
        case 0x20000000:
        case 0x40000000:
        case 0x60000000:
		inm->s_addr = htonl(0xFF000000);
		break;
		
	case 0x80000000:	/* Class B addr */
        case 0xA0000000:
		inm->s_addr = htonl(0xFFFF0000);
		break;
		
	case 0xC0000000:	/* Class C addr */
		inm->s_addr = htonl(0xFFFFFF00);
		break;
		
	default:		/* ??? */
		inm->s_addr = htonl(0xFFFFFFF0);
        }
}


/****************************************************************************
  get the broadcast address for our address 
([e-mail])
****************************************************************************/
static void get_broadcast(struct in_addr *if_ipaddr,
			  struct in_addr *if_bcast,
			  struct in_addr *if_nmask)
{  
	uint32 nm;
	short onbc;
	short offbc;

	/* get a default netmask and broadcast */
	default_netmask(if_nmask, if_ipaddr);

	get_netmask(if_ipaddr, if_nmask);

	/* sanity check on the netmask */
	nm = ntohl(if_nmask->s_addr);
	onbc = 0;
	offbc = 0;
	while((onbc + offbc) < 32) {
		if(nm & 0x80000000) {
			onbc++;
			if(offbc) {
				/* already found an off bit, so mask
                                   is wrong */
				onbc = 34;
			}
		} else {
			offbc++;
		}
		nm <<= 1;
	}
	if ((onbc < 8)||(onbc == 34)) {
		DEBUG(0,("Impossible netmask %s - using defaults\n",
			 inet_ntoa(*if_nmask)));
		default_netmask(if_nmask, if_ipaddr);      
	}

	/* derive the broadcast assuming a 1's broadcast, as this is what
	   all MS operating systems do, we have to comply even if the unix
	   box is setup differently */
	if_bcast->s_addr = MKBCADDR(if_ipaddr->s_addr, if_nmask->s_addr);
  
	DEBUG(4,("Derived broadcast address %s\n", inet_ntoa(*if_bcast)));
}



/****************************************************************************
load a list of network interfaces
****************************************************************************/
static void interpret_interfaces(char *s, struct interface **interfaces,
		char *description)
{
  char *ptr;
  fstring token;
  struct interface *iface;
  struct in_addr ip;

  ptr = s;
  ipzero = *interpret_addr2("0.0.0.0");
  allones_ip = *interpret_addr2("255.255.255.255");
  loopback_ip = *interpret_addr2("127.0.0.1");

  while (next_token(&ptr,token,NULL,sizeof(token))) {
    /* parse it into an IP address/netmasklength pair */
    char *p = strchr(token,'/');
    if (p) *p++ = 0;

    ip = *interpret_addr2(token);

    /* maybe we already have it listed */
    {
      struct interface *i;
      for (i=(*interfaces);i;i=i->next)
	if (ip_equal(ip,i->ip)) break;
      if (i) continue;
    }

    iface = (struct interface *)malloc(sizeof(*iface));
    if (!iface) return;

    iface->ip = ip;

    if (p) {
      if (strlen(p) > 2)
       iface->nmask = *interpret_addr2(p);
      else
       iface->nmask.s_addr = htonl(((ALLONES >> atoi(p)) ^ ALLONES));
    } else {
      default_netmask(&iface->nmask,&iface->ip);
    }
    iface->bcast.s_addr = MKBCADDR(iface->ip.s_addr, iface->nmask.s_addr);
    iface->next = NULL;

    if (!(*interfaces)) {
      (*interfaces) = iface;
    } else {
      last_iface->next = iface;
    }
    last_iface = iface;
    DEBUG(2,("Added %s ip=%s ",description,inet_ntoa(iface->ip)));
    DEBUG(2,("bcast=%s ",inet_ntoa(iface->bcast)));
    DEBUG(2,("nmask=%s\n",inet_ntoa(iface->nmask)));	     
  }

  if (*interfaces) return;

  /* setup a default interface */
  iface = (struct interface *)malloc(sizeof(*iface));
  if (!iface) return;

  iface->next = NULL;

  if (got_ip) {
    iface->ip = default_ip;
  } else {
    get_myname(NULL,&iface->ip);
  }

  if (got_bcast) {
    iface->bcast = default_bcast;
  } else {
    get_broadcast(&iface->ip,&iface->bcast,&iface->nmask);
  }

  if (got_nmask) {
    iface->nmask = default_nmask;
    iface->bcast.s_addr = MKBCADDR(iface->ip.s_addr, iface->nmask.s_addr);
  }

  if (iface->bcast.s_addr != MKBCADDR(iface->ip.s_addr, iface->nmask.s_addr)) {
    DEBUG(2,("Warning: inconsistant interface %s\n",inet_ntoa(iface->ip)));
  }

  iface->next = NULL;
  (*interfaces) = last_iface = iface;

  DEBUG(2,("Added interface ip=%s ",inet_ntoa(iface->ip)));
  DEBUG(2,("bcast=%s ",inet_ntoa(iface->bcast)));
  DEBUG(2,("nmask=%s\n",inet_ntoa(iface->nmask)));	     
}


/****************************************************************************
load the remote and local interfaces
****************************************************************************/
void load_interfaces(void)
{
  /* add the machine's interfaces to local interface structure*/
  interpret_interfaces(lp_interfaces(), &local_interfaces,"interface");
}


/****************************************************************************
  override the defaults
  **************************************************************************/
void iface_set_default(char *ip,char *bcast,char *nmask)
{
  if (ip) {
    got_ip = True;
    default_ip = *interpret_addr2(ip);
  }

  if (bcast) {
    got_bcast = True;
    default_bcast = *interpret_addr2(bcast);
  }

  if (nmask) {
    got_nmask = True;
    default_nmask = *interpret_addr2(nmask);
  }
}


/****************************************************************************
  check if an IP is one of mine
  **************************************************************************/
BOOL ismyip(struct in_addr ip)
{
  struct interface *i;
  for (i=local_interfaces;i;i=i->next)
    if (ip_equal(i->ip,ip)) return True;
  return False;
}

/****************************************************************************
  check if a packet is from a local (known) net
  **************************************************************************/
BOOL is_local_net(struct in_addr from)
{
  struct interface *i;
  for (i=local_interfaces;i;i=i->next)
    if((from.s_addr & i->nmask.s_addr) == (i->ip.s_addr & i->nmask.s_addr))
      return True;
  return False;
}

/****************************************************************************
  how many interfaces do we have
  **************************************************************************/
int iface_count(void)
{
  int ret = 0;
  struct interface *i;

  for (i=local_interfaces;i;i=i->next)
    ret++;
  return ret;
}

/****************************************************************************
 True if we have two or more interfaces.
  **************************************************************************/
BOOL we_are_multihomed(void)
{
  static int multi = -1;

  if(multi == -1)
    multi = (iface_count() > 1 ? True : False);

  return multi;
}

/****************************************************************************
  return the Nth interface
  **************************************************************************/
struct interface *get_interface(int n)
{ 
  struct interface *i;
  
  for (i=local_interfaces;i && n;i=i->next)
    n--;

  if (i) return i;
  return NULL;
}

/****************************************************************************
  return IP of the Nth interface
  **************************************************************************/
struct in_addr *iface_n_ip(int n)
{
  struct interface *i;
  
  for (i=local_interfaces;i && n;i=i->next)
    n--;

  if (i) return &i->ip;
  return NULL;
}

/****************************************************************************
Try and find an interface that matches an ip. If we cannot, return NULL
  **************************************************************************/
static struct interface *iface_find(struct in_addr ip)
{
  struct interface *i;
  if (zero_ip(ip)) return local_interfaces;

  for (i=local_interfaces;i;i=i->next)
    if (same_net(i->ip,ip,i->nmask)) return i;

  return NULL;
}


/****************************************************************************
this function provides a simple hash of the configured interfaces. It is
used to detect a change in interfaces to tell us whether to discard
the current wins.dat file.
Note that the result is independent of the order of the interfaces
  **************************************************************************/
unsigned iface_hash(void)
{
	unsigned ret = 0;
	struct interface *i;

	for (i=local_interfaces;i;i=i->next) {
		unsigned x1 = (unsigned)str_checksum(inet_ntoa(i->ip));
		unsigned x2 = (unsigned)str_checksum(inet_ntoa(i->nmask));
		ret ^= (x1 ^ x2);
	}

	return ret;
}


/* these 3 functions return the ip/bcast/nmask for the interface
   most appropriate for the given ip address. If they can't find
   an appropriate interface they return the requested field of the
   first known interface. */

struct in_addr *iface_bcast(struct in_addr ip)
{
  struct interface *i = iface_find(ip);
  return(i ? &i->bcast : &local_interfaces->bcast);
}

struct in_addr *iface_ip(struct in_addr ip)
{
  struct interface *i = iface_find(ip);
  return(i ? &i->ip : &local_interfaces->ip);
}