Fix regression in dhcp_lease_time utility.

CHANGELOG

@@ -2,6 +2,15 @@ version 2.67
 	    Fix crash if upstream server returns SERVFAIL when
 	    --conntrack in use. Thanks to Giacomo Tazzari for finding
 	    this and supplying the patch. 
+
+	    Repair regression in 2.64. That release stopped sending
+	    lease-time information in the reply to DHCPINFORM
+	    requests, on the correct grounds that it was a standards
+	    violation. However, this broke the dnsmasq-specific
+	    dhcp_lease_time utility. Now, DHCPINFORM returns
+	    lease-time only if it's specifically requested
+	    (maintaining standards) and the dhcp_lease_time utility
+	    has been taught to ask for it (restoring functionality). 
 	
 
 version 2.66

contrib/wrt/dhcp_lease_time.c

@@ -20,7 +20,7 @@
    nothing is sent to stdout a message is sent to stderr and a
    non-zero error code is returned.
 
-   Requires dnsmasq 2.40 or later. 
+   This version requires dnsmasq 2.67 or later. 
 */
 
 #include <sys/types.h> 
@@ -46,6 +46,7 @@
 #define OPTION_LEASE_TIME        51
 #define OPTION_OVERLOAD          52
 #define OPTION_MESSAGE_TYPE      53
+#define OPTION_REQUESTED_OPTIONS 55
 #define OPTION_END               255
 #define DHCPINFORM               8
 #define DHCP_SERVER_PORT         67
@@ -167,6 +168,12 @@ int main(int argc, char **argv)
   *(p++) = 1;
   *(p++) = DHCPINFORM;
 
+  /* Explicity request the lease time, it won't be sent otherwise:
+     this is a dnsmasq extension, not standard. */
+  *(p++) = OPTION_REQUESTED_OPTIONS;
+  *(p++) = 1;
+  *(p++) = OPTION_LEASE_TIME;
+  
   *(p++) = OPTION_END;
  
   dest.sin_family = AF_INET; 

src/rfc2131.c

@@ -39,6 +39,7 @@ static unsigned char *option_find(struct dhcp_packet *mess, size_t size, int opt
 static unsigned char *option_find1(unsigned char *p, unsigned char *end, int opt, int minsize);
 static size_t dhcp_packet_size(struct dhcp_packet *mess, unsigned char *agent_id, unsigned char *real_end);
 static void clear_packet(struct dhcp_packet *mess, unsigned char *end);
+static int in_list(unsigned char *list, int opt);
 static void do_options(struct dhcp_context *context,
 		       struct dhcp_packet *mess,
 		       unsigned char *real_end, 
@@ -1410,7 +1411,21 @@ size_t dhcp_reply(struct dhcp_context *context, char *iface_name, int int_index,
       clear_packet(mess, end);
       option_put(mess, end, OPTION_MESSAGE_TYPE, 1, DHCPACK);
       option_put(mess, end, OPTION_SERVER_IDENTIFIER, INADDRSZ, ntohl(server_id(context, override, fallback).s_addr));
-      
+     
+      /* RFC 2131 says that DHCPINFORM shouldn't include lease-time parameters, but 
+	 we supply a utility which makes DHCPINFORM requests to get this information.
+	 Only include lease time if OPTION_LEASE_TIME is in the parameter request list,
+	 which won't be true for ordinary clients, but will be true for the 
+	 dhcp_lease_time utility. */
+      if (lease && in_list(req_options, OPTION_LEASE_TIME))
+	{
+	  if (lease->expires == 0)
+	    time = 0xffffffff;
+	  else
+	    time = (unsigned int)difftime(lease->expires, now);
+	  option_put(mess, end, OPTION_LEASE_TIME, 4, time);
+	}
+
       do_options(context, mess, end, req_options, hostname, get_domain(mess->ciaddr),
 		 netid, subnet_addr, fqdn_flags, borken_opt, pxearch, uuid, vendor_class_len, now);