Suppress DHCP ping checks when allocating on the loopback interface.

src/dhcp.c

@@ -145,7 +145,7 @@ void dhcp_packet(time_t now, int pxe_fd)
   struct cmsghdr *cmptr;
   struct iovec iov;
   ssize_t sz; 
-  int iface_index = 0, unicast_dest = 0, is_inform = 0;
+  int iface_index = 0, unicast_dest = 0, is_inform = 0, loopback = 0;
   int rcvd_iface_index;
   struct in_addr iface_addr;
   struct iface_param parm;
@@ -223,9 +223,13 @@ void dhcp_packet(time_t now, int pxe_fd)
 	}
 #endif
 	
-  if (!indextoname(daemon->dhcpfd, iface_index, ifr.ifr_name))
+  if (!indextoname(daemon->dhcpfd, iface_index, ifr.ifr_name) ||
+      ioctl(daemon->dhcpfd, SIOCGIFFLAGS, &ifr) != -1)
     return;
-
+  
+  mess = (struct dhcp_packet *)daemon->dhcp_packet.iov_base;
+  loopback = !mess->giaddr.s_addr && (ifr.ifr_flags & IFF_LOOPBACK);
+  
 #ifdef HAVE_LINUX_NETWORK
   /* ARP fiddling uses original interface even if we pretend to use a different one. */
   strncpy(arp_req.arp_dev, ifr.ifr_name, 16);
@@ -331,7 +335,7 @@ void dhcp_packet(time_t now, int pxe_fd)
 
       /* We're relaying this request */
       if  (parm.relay_local.s_addr != 0 &&
-	   relay_upstream4(parm.relay, (struct dhcp_packet *)daemon->dhcp_packet.iov_base, (size_t)sz, iface_index))
+	   relay_upstream4(parm.relay, mess, (size_t)sz, iface_index))
 	return;
 
       /* May have configured relay, but not DHCP server */
@@ -340,7 +344,7 @@ void dhcp_packet(time_t now, int pxe_fd)
 
       lease_prune(NULL, now); /* lose any expired leases */
       iov.iov_len = dhcp_reply(parm.current, ifr.ifr_name, iface_index, (size_t)sz, 
-			       now, unicast_dest, &is_inform, pxe_fd, iface_addr, recvtime);
+			       now, unicast_dest, loopback, &is_inform, pxe_fd, iface_addr, recvtime);
       lease_update_file(now);
       lease_update_dns(0);
       
@@ -647,7 +651,7 @@ struct dhcp_config *config_find_by_address(struct dhcp_config *configs, struct i
    This wrapper handles a cache and load-limiting.
    Return is NULL is address in use, or a pointer to a cache entry
    recording that it isn't. */
-struct ping_result *do_icmp_ping(time_t now, struct in_addr addr, unsigned int hash)
+struct ping_result *do_icmp_ping(time_t now, struct in_addr addr, unsigned int hash, int loopback)
 {
   static struct ping_result dummy;
   struct ping_result *r, *victim = NULL;
@@ -671,9 +675,9 @@ struct ping_result *do_icmp_ping(time_t now, struct in_addr addr, unsigned int h
       }
   
   /* didn't find cached entry */
-  if ((count >= max) || option_bool(OPT_NO_PING))
+  if ((count >= max) || option_bool(OPT_NO_PING) || loopback)
     {
-      /* overloaded, or configured not to check, return "not in use" */
+      /* overloaded, or configured not to check, loopback interface, return "not in use" */
       dummy.hash = 0;
       return &dummy;
     }
@@ -705,7 +709,7 @@ struct ping_result *do_icmp_ping(time_t now, struct in_addr addr, unsigned int h
 
 int address_allocate(struct dhcp_context *context,
 		     struct in_addr *addrp, unsigned char *hwaddr, int hw_len, 
-		     struct dhcp_netid *netids, time_t now)   
+		     struct dhcp_netid *netids, time_t now, int loopback)   
 {
   /* Find a free address: exclude anything in use and anything allocated to
      a particular hwaddr/clientid/hostname in our configuration.
@@ -763,7 +767,7 @@ int address_allocate(struct dhcp_context *context,
 	      {
 		struct ping_result *r;
 		
-		if ((r = do_icmp_ping(now, addr, j)))
+		if ((r = do_icmp_ping(now, addr, j, loopback)))
  		  {
 		    /* consec-ip mode: we offered this address for another client
 		       (different hash) recently, don't offer it to this one. */

src/dnsmasq.h

@@ -1292,10 +1292,10 @@ struct dhcp_context *narrow_context(struct dhcp_context *context,
 				    struct in_addr taddr,
 				    struct dhcp_netid *netids);
 struct ping_result *do_icmp_ping(time_t now, struct in_addr addr,
-				 unsigned int hash);
+				 unsigned int hash, int loopback);
 int address_allocate(struct dhcp_context *context,
 		     struct in_addr *addrp, unsigned char *hwaddr, int hw_len,
-		     struct dhcp_netid *netids, time_t now);
+		     struct dhcp_netid *netids, time_t now, int loopback);
 void dhcp_read_ethers(void);
 struct dhcp_config *config_find_by_address(struct dhcp_config *configs, struct in_addr addr);
 char *host_from_dns(struct in_addr addr);
@@ -1344,7 +1344,8 @@ void lease_add_extradata(struct dhcp_lease *lease, unsigned char *data,
 /* rfc2131.c */
 #ifdef HAVE_DHCP
 size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
-		  size_t sz, time_t now, int unicast_dest, int *is_inform, int pxe_fd, struct in_addr fallback, time_t recvtime);
+		  size_t sz, time_t now, int unicast_dest, int loopback,
+		  int *is_inform, int pxe_fd, struct in_addr fallback, time_t recvtime);
 unsigned char *extended_hwaddr(int hwtype, int hwlen, unsigned char *hwaddr, 
 			       int clid_len, unsigned char *clid, int *len_out);
 #endif

src/rfc2131.c

@@ -67,7 +67,8 @@ static int pxe_uefi_workaround(int pxe_arch, struct dhcp_netid *netid, struct dh
 static void apply_delay(u32 xid, time_t recvtime, struct dhcp_netid *netid);
 
 size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
-		  size_t sz, time_t now, int unicast_dest, int *is_inform, int pxe, struct in_addr fallback, time_t recvtime)
+		  size_t sz, time_t now, int unicast_dest, int loopback,
+		  int *is_inform, int pxe, struct in_addr fallback, time_t recvtime)
 {
   unsigned char *opt, *clid = NULL;
   struct dhcp_lease *ltmp, *lease = NULL;
@@ -575,7 +576,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 		       lease_prune(lease, now);
 		       lease = NULL;
 		     }
-		   if (!address_allocate(context, &mess->yiaddr, mess->chaddr, mess->hlen, tagif_netid, now))
+		   if (!address_allocate(context, &mess->yiaddr, mess->chaddr, mess->hlen, tagif_netid, now, loopback))
 		     message = _("no address available");
 		}
 	      else
@@ -1036,7 +1037,7 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 		  else if (have_config(config, CONFIG_DECLINED) &&
 			   difftime(now, config->decline_time) < (float)DECLINE_BACKOFF)
 		    my_syslog(MS_DHCP | LOG_WARNING, _("not using configured address %s because it was previously declined"), addrs);
-		  else if (!do_icmp_ping(now, config->addr, 0))
+		  else if (!do_icmp_ping(now, config->addr, 0, loopback))
 		    my_syslog(MS_DHCP | LOG_WARNING, _("not using configured address %s because it is in use by another host"), addrs);
 		  else
 		    conf = config->addr;
@@ -1050,11 +1051,11 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
 		   !config_find_by_address(daemon->dhcp_conf, lease->addr))
 	    mess->yiaddr = lease->addr;
 	  else if (opt && address_available(context, addr, tagif_netid) && !lease_find_by_addr(addr) && 
-		   !config_find_by_address(daemon->dhcp_conf, addr) && do_icmp_ping(now, addr, 0))
+		   !config_find_by_address(daemon->dhcp_conf, addr) && do_icmp_ping(now, addr, 0, loopback))
 	    mess->yiaddr = addr;
 	  else if (emac_len == 0)
 	    message = _("no unique-id");
-	  else if (!address_allocate(context, &mess->yiaddr, emac, emac_len, tagif_netid, now))
+	  else if (!address_allocate(context, &mess->yiaddr, emac, emac_len, tagif_netid, now, loopback))
 	    message = _("no address available");      
 	}