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Cache access to the kernel's ARP table.
This commit is contained in:
Simon Kelley
201
src/arp.c
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201
src/arp.c
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/* dnsmasq is Copyright (c) 2000-2015 Simon Kelley
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 dated June, 1991, or
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(at your option) version 3 dated 29 June, 2007.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "dnsmasq.h"
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#define ARP_FREE 0
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#define ARP_FOUND 1
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#define ARP_NEW 2
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#define ARP_EMPTY 3
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struct arp_record {
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short hwlen, status;
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int family;
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unsigned char hwaddr[DHCP_CHADDR_MAX];
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struct all_addr addr;
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struct arp_record *next;
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};
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static struct arp_record *arps = NULL, *old = NULL;
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static int filter_mac(int family, char *addrp, char *mac, size_t maclen, void *parmv)
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{
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int match = 0;
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struct arp_record *arp;
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if (maclen > DHCP_CHADDR_MAX)
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return 1;
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/* Look for existing entry */
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for (arp = arps; arp; arp = arp->next)
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{
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if (family != arp->family || arp->status == ARP_NEW)
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continue;
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if (family == AF_INET)
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{
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if (arp->addr.addr.addr4.s_addr != ((struct in_addr *)addrp)->s_addr)
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continue;
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}
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#ifdef HAVE_IPV6
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else
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{
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if (!IN6_ARE_ADDR_EQUAL(&arp->addr.addr.addr6, (struct in6_addr *)addrp))
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continue;
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}
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#endif
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if (arp->status != ARP_EMPTY && arp->hwlen == maclen && memcmp(arp->hwaddr, mac, maclen) == 0)
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arp->status = ARP_FOUND;
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else
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{
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/* existing address, MAC changed or arrived new. */
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arp->status = ARP_NEW;
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arp->hwlen = maclen;
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arp->family = family;
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memcpy(arp->hwaddr, mac, maclen);
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}
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break;
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}
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if (!arp)
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{
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/* New entry */
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if (old)
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{
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arp = old;
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old = old->next;
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}
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else if (!(arp = whine_malloc(sizeof(struct arp_record))))
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return 1;
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arp->next = arps;
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arps = arp;
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arp->status = ARP_NEW;
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arp->hwlen = maclen;
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arp->family = family;
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memcpy(arp->hwaddr, mac, maclen);
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if (family == AF_INET)
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arp->addr.addr.addr4.s_addr = ((struct in_addr *)addrp)->s_addr;
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#ifdef HAVE_IPV6
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else
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memcpy(&arp->addr.addr.addr6, addrp, IN6ADDRSZ);
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#endif
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}
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return 1;
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}
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/* If in lazy mode, we cache absence of ARP entries. */
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int find_mac(union mysockaddr *addr, unsigned char *mac, int lazy)
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{
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struct arp_record *arp, **up;
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int updated = 0;
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again:
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for (arp = arps; arp; arp = arp->next)
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{
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if (addr->sa.sa_family == arp->family)
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{
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if (arp->addr.addr.addr4.s_addr != addr->in.sin_addr.s_addr)
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continue;
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}
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#ifdef HAVE_IPV6
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else
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{
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if (!IN6_ARE_ADDR_EQUAL(&arp->addr.addr.addr6, &addr->in6.sin6_addr))
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continue;
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}
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#endif
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/* Only accept poitive entries unless in lazy mode. */
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if (arp->status != ARP_EMPTY || lazy || updated)
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{
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if (mac && arp->hwlen != 0)
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memcpy(mac, arp->hwaddr, arp->hwlen);
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return arp->hwlen;
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}
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}
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/* Not found, try the kernel */
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if (!updated)
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{
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updated = 1;
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/* Mark all non-negative entries */
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for (arp = arps, up = &arps; arp; arp = arp->next)
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if (arp->status != ARP_EMPTY)
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arp->status = ARP_FREE;
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iface_enumerate(AF_UNSPEC, NULL, filter_mac);
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/* Remove all unconfirmed entries to old list, announce new ones. */
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for (arp = arps, up = &arps; arp; arp = arp->next)
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if (arp->status == ARP_FREE)
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{
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*up = arp->next;
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arp->next = old;
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old = arp;
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}
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else
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{
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up = &arp->next;
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if (arp->status == ARP_NEW)
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{
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char a[ADDRSTRLEN], m[ADDRSTRLEN];
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union mysockaddr pa;
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pa.sa.sa_family = arp->family;
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pa.in.sin_addr.s_addr = arp->addr.addr.addr4.s_addr;
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prettyprint_addr(&pa, a);
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print_mac(m, arp->hwaddr, arp->hwlen);
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my_syslog(LOG_INFO, _("new arp: %s %s"), a, m);
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}
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}
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goto again;
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}
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/* record failure, so we don't consult the kernel each time
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we're asked for this address */
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if (old)
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{
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arp = old;
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old = old->next;
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}
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else
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arp = whine_malloc(sizeof(struct arp_record));
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if (arp)
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{
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arp->next = arps;
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arps = arp;
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arp->status = ARP_EMPTY;
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arp->family = addr->sa.sa_family;
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if (addr->sa.sa_family == AF_INET)
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arp->addr.addr.addr4.s_addr = addr->in.sin_addr.s_addr;
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#ifdef HAVE_IPV6
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else
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memcpy(&arp->addr.addr.addr6, &addr->in6.sin6_addr, IN6ADDRSZ);
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#endif
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}
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return 0;
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}
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