source: vendor/3.6.0/source4/lib/socket/interface.c

/* 
   Unix SMB/CIFS implementation.

   multiple interface handling

   Copyright (C) Andrew Tridgell 1992-2005
   
   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "system/network.h"
#include "lib/socket/netif.h"
#include "../lib/util/util_net.h"
#include "../lib/util/dlinklist.h"

/** used for network interfaces */
struct interface {
        struct interface *next, *prev;
        struct in_addr ip;
        struct in_addr nmask;
        const char *ip_s;
        const char *bcast_s;
        const char *nmask_s;
};

#define ALLONES  ((uint32_t)0xFFFFFFFF)
/*
  address construction based on a patch from fred@datalync.com
*/
#define MKBCADDR(_IP, _NM) ((_IP & _NM) | (_NM ^ ALLONES))
#define MKNETADDR(_IP, _NM) (_IP & _NM)

/****************************************************************************
Try and find an interface that matches an ip. If we cannot, return NULL
  **************************************************************************/
static struct interface *iface_find(struct interface *interfaces, 
                                    struct in_addr ip, bool CheckMask)
{
        struct interface *i;
        if (is_zero_ip_v4(ip)) return interfaces;

        for (i=interfaces;i;i=i->next)
                if (CheckMask) {
                        if (same_net_v4(i->ip,ip,i->nmask)) return i;
                } else if (i->ip.s_addr == ip.s_addr) return i;

        return NULL;
}


/****************************************************************************
add an interface to the linked list of interfaces
****************************************************************************/
static void add_interface(TALLOC_CTX *mem_ctx, struct in_addr ip, struct in_addr nmask, struct interface **interfaces)
{
        struct interface *iface;
        struct in_addr bcast;

        if (iface_find(*interfaces, ip, false)) {
                DEBUG(3,("not adding duplicate interface %s\n",inet_ntoa(ip)));
                return;
        }

        iface = talloc(*interfaces == NULL ? mem_ctx : *interfaces, struct interface);
        if (iface == NULL) 
                return;
        
        ZERO_STRUCTPN(iface);

        iface->ip = ip;
        iface->nmask = nmask;
        bcast.s_addr = MKBCADDR(iface->ip.s_addr, iface->nmask.s_addr);

        /* keep string versions too, to avoid people tripping over the implied
           static in inet_ntoa() */
        iface->ip_s = talloc_strdup(iface, inet_ntoa(iface->ip));
        iface->nmask_s = talloc_strdup(iface, inet_ntoa(iface->nmask));
        
        if (nmask.s_addr != ~0) {
                iface->bcast_s = talloc_strdup(iface, inet_ntoa(bcast));
        }

        DLIST_ADD_END(*interfaces, iface, struct interface *);

        DEBUG(3,("added interface ip=%s nmask=%s\n", iface->ip_s, iface->nmask_s));
}



/**
interpret a single element from a interfaces= config line 

This handles the following different forms:

1) wildcard interface name
2) DNS name
3) IP/masklen
4) ip/mask
5) bcast/mask
**/
static void interpret_interface(TALLOC_CTX *mem_ctx, 
                                const char *token, 
                                struct iface_struct *probed_ifaces, 
                                int total_probed,
                                struct interface **local_interfaces)
{
        struct in_addr ip, nmask;
        char *p;
        char *address;
        int i, added=0;

        ip.s_addr = 0;
        nmask.s_addr = 0;
        
        /* first check if it is an interface name */
        for (i=0;i<total_probed;i++) {
                if (gen_fnmatch(token, probed_ifaces[i].name) == 0) {
                        add_interface(mem_ctx, probed_ifaces[i].ip,
                                      probed_ifaces[i].netmask,
                                      local_interfaces);
                        added = 1;
                }
        }
        if (added) return;

        /* maybe it is a DNS name */
        p = strchr_m(token,'/');
        if (!p) {
                /* don't try to do dns lookups on wildcard names */
                if (strpbrk(token, "*?") != NULL) {
                        return;
                }
                ip.s_addr = interpret_addr2(token).s_addr;
                for (i=0;i<total_probed;i++) {
                        if (ip.s_addr == probed_ifaces[i].ip.s_addr) {
                                add_interface(mem_ctx, probed_ifaces[i].ip,
                                              probed_ifaces[i].netmask,
                                              local_interfaces);
                                return;
                        }
                }
                DEBUG(2,("can't determine netmask for %s\n", token));
                return;
        }

        address = talloc_strdup(mem_ctx, token);
        p = strchr_m(address,'/');

        /* parse it into an IP address/netmasklength pair */
        *p++ = 0;

        ip.s_addr = interpret_addr2(address).s_addr;

        if (strlen(p) > 2) {
                nmask.s_addr = interpret_addr2(p).s_addr;
        } else {
                nmask.s_addr = htonl(((ALLONES >> atoi(p)) ^ ALLONES));
        }

        /* maybe the first component was a broadcast address */
        if (ip.s_addr == MKBCADDR(ip.s_addr, nmask.s_addr) ||
            ip.s_addr == MKNETADDR(ip.s_addr, nmask.s_addr)) {
                for (i=0;i<total_probed;i++) {
                        if (same_net_v4(ip, probed_ifaces[i].ip, nmask)) {
                                add_interface(mem_ctx, probed_ifaces[i].ip, nmask,
                                              local_interfaces);
                                talloc_free(address);
                                return;
                        }
                }
                DEBUG(2,("Can't determine ip for broadcast address %s\n", address));
                talloc_free(address);
                return;
        }

        add_interface(mem_ctx, ip, nmask, local_interfaces);
        talloc_free(address);
}


/**
load the list of network interfaces
**/
void load_interfaces(TALLOC_CTX *mem_ctx, const char **interfaces, struct interface **local_interfaces)
{
        const char **ptr = interfaces;
        int i;
        struct iface_struct ifaces[MAX_INTERFACES];
        struct in_addr loopback_ip;
        int total_probed;

        *local_interfaces = NULL;

        loopback_ip = interpret_addr2("127.0.0.1");

        /* probe the kernel for interfaces */
        total_probed = get_interfaces(ifaces, MAX_INTERFACES);

        /* if we don't have a interfaces line then use all interfaces
           except loopback */
        if (!ptr || !*ptr || !**ptr) {
                if (total_probed <= 0) {
                        DEBUG(0,("ERROR: Could not determine network interfaces, you must use a interfaces config line\n"));
                }
                for (i=0;i<total_probed;i++) {
                        if (ifaces[i].ip.s_addr != loopback_ip.s_addr) {
                                add_interface(mem_ctx, ifaces[i].ip, 
                                              ifaces[i].netmask, local_interfaces);
                        }
                }
        }

        while (ptr && *ptr) {
                interpret_interface(mem_ctx, *ptr, ifaces, total_probed, local_interfaces);
                ptr++;
        }

        if (!*local_interfaces) {
                DEBUG(0,("WARNING: no network interfaces found\n"));
        }
}

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

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

/**
  return IP of the Nth interface
  **/
const char *iface_n_ip(struct interface *ifaces, int n)
{
        struct interface *i;
  
        for (i=ifaces;i && n;i=i->next)
                n--;

        if (i) {
                return i->ip_s;
        }
        return NULL;
}

/**
  return bcast of the Nth interface
  **/
const char *iface_n_bcast(struct interface *ifaces, int n)
{
        struct interface *i;
  
        for (i=ifaces;i && n;i=i->next)
                n--;

        if (i) {
                return i->bcast_s;
        }
        return NULL;
}

/**
  return netmask of the Nth interface
  **/
const char *iface_n_netmask(struct interface *ifaces, int n)
{
        struct interface *i;
  
        for (i=ifaces;i && n;i=i->next)
                n--;

        if (i) {
                return i->nmask_s;
        }
        return NULL;
}

/**
  return the local IP address that best matches a destination IP, or
  our first interface if none match
*/
const char *iface_best_ip(struct interface *ifaces, const char *dest)
{
        struct interface *iface;
        struct in_addr ip;

        ip.s_addr = interpret_addr(dest);
        iface = iface_find(ifaces, ip, true);
        if (iface) {
                return iface->ip_s;
        }
        return iface_n_ip(ifaces, 0);
}

/**
  return true if an IP is one one of our local networks
*/
bool iface_is_local(struct interface *ifaces, const char *dest)
{
        struct in_addr ip;

        ip.s_addr = interpret_addr(dest);
        if (iface_find(ifaces, ip, true)) {
                return true;
        }
        return false;
}

/**
  return true if a IP matches a IP/netmask pair
*/
bool iface_same_net(const char *ip1, const char *ip2, const char *netmask)
{
        return same_net_v4(interpret_addr2(ip1),
                        interpret_addr2(ip2),
                        interpret_addr2(netmask));
}