Enhance --hostdir so that records are automatically removed when re-reading.

Initial patch from Dominik Derigs, re-written by Simon Kelley.

CHANGELOG

@@ -18,6 +18,10 @@ version 2.88
 	flushed when its TTL expires, so the cache becomes
 	strictly least-recently-used.
 
+	Make --hostsdir (but NOT --dhcp-hostsdir and --dhcp-optsdir)
+	handle removal of whole files or entries within files.
+	Thanks to Dominik Derigs for the initial patches for this.
+
 	
 version 2.87
         Allow arbitrary prefix lengths in --rev-server and

man/dnsmasq.8

@@ -60,7 +60,8 @@ in alphabetical order.
 .TP
 .B --hostsdir=<path>
 Read all the hosts files contained in the directory. New or changed files
-are read automatically. See \fB--dhcp-hostsdir\fP for details.
+are read automatically and modified and deleted files have removed records
+automatically deleted.
 .TP
 .B \-E, --expand-hosts
 Add the domain to simple names (without a period) in /etc/hosts

src/cache.c

@@ -388,6 +388,27 @@ static int is_expired(time_t now, struct crec *crecp)
   return 1;
 }
 
+/* Remove entries with a given UID from the cache */
+unsigned int cache_remove_uid(const unsigned int uid)
+{
+  int i;
+  unsigned int removed = 0;
+  struct crec *crecp, **up;
+
+  for (i = 0; i < hash_size; i++)
+    for (crecp = hash_table[i], up = &hash_table[i]; crecp; crecp = crecp->hash_next)
+      if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) && crecp->uid == uid)
+	{
+	  *up = crecp->hash_next;
+	  free(crecp);
+	  removed++;
+	}
+      else
+	up = &crecp->hash_next;
+  
+  return removed;
+}
+
 static struct crec *cache_scan_free(char *name, union all_addr *addr, unsigned short class, time_t now,
 				    unsigned int flags, struct crec **target_crec, unsigned int *target_uid)
 {

src/dnsmasq.h

@@ -1304,6 +1304,7 @@ struct crec *cache_find_by_name(struct crec *crecp,
 				char *name, time_t now, unsigned int prot);
 void cache_end_insert(void);
 void cache_start_insert(void);
+unsigned int cache_remove_uid(const unsigned int uid);
 int cache_recv_insert(time_t now, int fd);
 struct crec *cache_insert(char *name, union all_addr *addr, unsigned short class, 
 			  time_t now, unsigned long ttl, unsigned int flags);

src/inotify.c

@@ -294,12 +294,16 @@ int inotify_check(time_t now)
 		    strcat(path, "/");
 		    strcat(path, in->name);
 		     
-		    my_syslog(LOG_INFO, _("inotify, new or changed file %s"), path);
+		    my_syslog(LOG_INFO, _("inotify: new, removed or changed file %s"), path);
 
 		    if (dd->flags & AH_HOSTS)
 		      {
 			if ((ah = dyndir_addhosts(dd, path)))
 			  {
+			    const unsigned int removed = cache_remove_uid(ah->index);
+			    if (removed > 0)
+			      my_syslog(LOG_INFO, _("flushed %u outdated entries"), removed);
+
 			    read_hostsfile(path, ah->index, 0, NULL, 0);
 #ifdef HAVE_DHCP
 			    if (daemon->dhcp || daemon->doing_dhcp6)