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/* dnsmasq is Copyright (c) 2000-2021 Simon Kelley
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; version 2 dated June, 1991, or
(at your option) version 3 dated 29 June, 2007.
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 "dnsmasq.h"
/* Time between forced re-loads from kernel. */
#define INTERVAL 90
#define ARP_MARK 0
#define ARP_FOUND 1 /* Confirmed */
#define ARP_NEW 2 /* Newly created */
#define ARP_EMPTY 3 /* No MAC addr */
struct arp_record {
unsigned short hwlen, status;
int family;
unsigned char hwaddr[DHCP_CHADDR_MAX];
union all_addr addr;
struct arp_record *next;
};
static struct arp_record *arps = NULL, *old = NULL, *freelist = NULL;
static time_t last = 0;
static int filter_mac(int family, char *addrp, char *mac, size_t maclen, void *parmv)
{
struct arp_record *arp;
(void)parmv;
if (maclen > DHCP_CHADDR_MAX)
return 1;
/* Look for existing entry */
for (arp = arps; arp; arp = arp->next)
{
if (family != arp->family || arp->status == ARP_NEW)
continue;
if (family == AF_INET)
{
if (arp->addr.addr4.s_addr != ((struct in_addr *)addrp)->s_addr)
continue;
}
else
{
if (!IN6_ARE_ADDR_EQUAL(&arp->addr.addr6, (struct in6_addr *)addrp))
continue;
}
if (arp->status == ARP_EMPTY)
{
/* existing address, was negative. */
arp->status = ARP_NEW;
arp->hwlen = maclen;
memcpy(arp->hwaddr, mac, maclen);
}
else if (arp->hwlen == maclen && memcmp(arp->hwaddr, mac, maclen) == 0)
/* Existing entry matches - confirm. */
arp->status = ARP_FOUND;
else
continue;
break;
}
if (!arp)
{
/* New entry */
if (freelist)
{
arp = freelist;
freelist = freelist->next;
}
else if (!(arp = whine_malloc(sizeof(struct arp_record))))
return 1;
arp->next = arps;
arps = arp;
arp->status = ARP_NEW;
arp->hwlen = maclen;
arp->family = family;
memcpy(arp->hwaddr, mac, maclen);
if (family == AF_INET)
arp->addr.addr4.s_addr = ((struct in_addr *)addrp)->s_addr;
else
memcpy(&arp->addr.addr6, addrp, IN6ADDRSZ);
}
return 1;
}
/* If in lazy mode, we cache absence of ARP entries. */
int find_mac(union mysockaddr *addr, unsigned char *mac, int lazy, time_t now)
{
struct arp_record *arp, *tmp, **up;
int updated = 0;
again:
/* If the database is less then INTERVAL old, look in there */
if (difftime(now, last) < INTERVAL)
{
/* addr == NULL -> just make cache up-to-date */
if (!addr)
return 0;
for (arp = arps; arp; arp = arp->next)
{
if (addr->sa.sa_family != arp->family)
continue;
if (arp->family == AF_INET &&
arp->addr.addr4.s_addr != addr->in.sin_addr.s_addr)
continue;
if (arp->family == AF_INET6 &&
!IN6_ARE_ADDR_EQUAL(&arp->addr.addr6, &addr->in6.sin6_addr))
continue;
/* Only accept positive entries unless in lazy mode. */
if (arp->status != ARP_EMPTY || lazy || updated)
{
if (mac && arp->hwlen != 0)
memcpy(mac, arp->hwaddr, arp->hwlen);
return arp->hwlen;
}
}
}
/* Not found, try the kernel */
if (!updated)
{
updated = 1;
last = now;
/* Mark all non-negative entries */
for (arp = arps; arp; arp = arp->next)
if (arp->status != ARP_EMPTY)
arp->status = ARP_MARK;
iface_enumerate(AF_UNSPEC, NULL, filter_mac);
/* Remove all unconfirmed entries to old list. */
for (arp = arps, up = &arps; arp; arp = tmp)
{
tmp = arp->next;
if (arp->status == ARP_MARK)
{
*up = arp->next;
arp->next = old;
old = arp;
}
else
up = &arp->next;
}
goto again;
}
/* record failure, so we don't consult the kernel each time
we're asked for this address */
if (freelist)
{
arp = freelist;
freelist = freelist->next;
}
else
arp = whine_malloc(sizeof(struct arp_record));
if (arp)
{
arp->next = arps;
arps = arp;
arp->status = ARP_EMPTY;
arp->family = addr->sa.sa_family;
arp->hwlen = 0;
if (addr->sa.sa_family == AF_INET)
arp->addr.addr4.s_addr = addr->in.sin_addr.s_addr;
else
memcpy(&arp->addr.addr6, &addr->in6.sin6_addr, IN6ADDRSZ);
}
return 0;
}
int do_arp_script_run(void)
{
struct arp_record *arp;
/* Notify any which went, then move to free list */
if (old)
{
#ifdef HAVE_SCRIPT
if (option_bool(OPT_SCRIPT_ARP))
queue_arp(ACTION_ARP_DEL, old->hwaddr, old->hwlen, old->family, &old->addr);
#endif
arp = old;
old = arp->next;
arp->next = freelist;
freelist = arp;
return 1;
}
for (arp = arps; arp; arp = arp->next)
if (arp->status == ARP_NEW)
{
#ifdef HAVE_SCRIPT
if (option_bool(OPT_SCRIPT_ARP))
queue_arp(ACTION_ARP, arp->hwaddr, arp->hwlen, arp->family, &arp->addr);
#endif
arp->status = ARP_FOUND;
return 1;
}
return 0;
}
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