Fix crash in PXE/netboot when DNS server disabled.

CHANGELOG

@@ -11,7 +11,11 @@ version 2.87
 	Add --filter-A and --filter-AAAA options, to remove IPv4 or IPv6
 	addresses from DNS answers.
 
+	Fix crash doing netbooting when --port is set to zero
+	to disable the DNS server. Thanks to Drexl Johannes
+	for the bug report.
 
+	
 version 2.86
 	Handle DHCPREBIND requests in the DHCPv6 server code.
 	Thanks to Aichun Li for spotting this omission, and the initial

debian/changelog

@@ -1,7 +1,8 @@
 dnsmasq (2.87-1) unstable; urgency=low
 
    * New upstream.
-   * Include new NFTset support in the build.  	
+   * Include new NFTset support in the build.
+   * Fix crash on netboot with DNS server disabled. (closes: #996332)
 
  -- Simon Kelley <simon@thekelleys.org.uk>  Wed, 08 Sep 2021 23:11:25 +0000
 

src/cache.c

@@ -1399,10 +1399,12 @@ struct in_addr a_record_from_hosts(char *name, time_t now)
   struct crec *crecp = NULL;
   struct in_addr ret;
   
-  while ((crecp = cache_find_by_name(crecp, name, now, F_IPV4)))
-    if (crecp->flags & F_HOSTS)
-      return crecp->addr.addr4;
-
+  /* If no DNS service, cache not initialised. */
+  if (daemon->port != 0)
+    while ((crecp = cache_find_by_name(crecp, name, now, F_IPV4)))
+      if (crecp->flags & F_HOSTS)
+	return crecp->addr.addr4;
+  
   my_syslog(MS_DHCP | LOG_WARNING, _("No IPv4 address found for %s"), name);
   
   ret.s_addr = 0;