Generalise locally-configured CNAME handling.

It's now possible for the target of a CNAME to be any locally
configured RR or even point to a non-existent RR.

man/dnsmasq.8

@@ -603,12 +603,9 @@ Return a CAA DNS record, as specified in RFC6844.
 .TP
 .B --cname=<cname>,[<cname>,]<target>[,<TTL>]
 Return a CNAME record which indicates that <cname> is really
-<target>. There are significant limitations on the target; it must be a
+<target>. There is a significant limitation on the target; it must be a
-DNS name which is known to dnsmasq from /etc/hosts (or additional
+DNS record which is known to dnsmasq and NOT a DNS record which comes from
-hosts files), from DHCP, from \fB--interface-name\fP or from another
+an upstream server. The cname must be unique, but it
-.B --cname.
-If the target does not satisfy this
-criteria, the whole cname is ignored. The cname must be unique, but it
 is permissible to have more than one cname pointing to the same target. Indeed
 it's possible to declare multiple cnames to a target in a single line, like so:
 .B --cname=cname1,cname2,target

src/cache.c

@@ -276,10 +276,10 @@ char *cache_get_name(struct crec *crecp)
 
 char *cache_get_cname_target(struct crec *crecp)
 {
-  if (crecp->addr.cname.uid != SRC_INTERFACE)
+  if (crecp->addr.cname.uid != SRC_PTR)
     return cache_get_name(crecp->addr.cname.target.cache);
 
-  return crecp->addr.cname.target.int_name->name;
+  return crecp->addr.cname.target.name;
 }
 
 
@@ -309,7 +309,7 @@ struct crec *cache_enumerate(int init)
 
 static int is_outdated_cname_pointer(struct crec *crecp)
 {
-  if (!(crecp->flags & F_CNAME) || crecp->addr.cname.uid == SRC_INTERFACE)
+  if (!(crecp->flags & F_CNAME) || crecp->addr.cname.uid == SRC_PTR)
     return 0;
   
   /* NB. record may be reused as DS or DNSKEY, where uid is 
@@ -513,7 +513,7 @@ static struct crec *really_insert(char *name, union all_addr *addr, unsigned sho
     {
       /* We're trying to insert a record over one from 
 	 /etc/hosts or DHCP, or other config. If the 
-	 existing record is for an A or AAAA and
+	 existing record is for an A or AAAA or CNAME and
 	 the record we're trying to insert is the same, 
 	 just drop the insert, but don't error the whole process. */
       if ((flags & (F_IPV4 | F_IPV6)) && (flags & F_FORWARD) && addr)
@@ -956,47 +956,19 @@ struct crec *cache_find_by_addr(struct crec *crecp, union all_addr *addr,
   return NULL;
 }
 
-static void add_hosts_cname(struct crec *target)
-{
-  struct crec *crec;
-  struct cname *a;
-  
-  for (a = daemon->cnames; a; a = a->next)
-    if (a->alias[1] != '*' &&
-	hostname_isequal(cache_get_name(target), a->target) &&
-	(crec = whine_malloc(SIZEOF_POINTER_CREC)))
-      {
-	crec->flags = F_FORWARD | F_IMMORTAL | F_NAMEP | F_CONFIG | F_CNAME;
-	crec->ttd = a->ttl;
-	crec->name.namep = a->alias;
-	crec->addr.cname.target.cache = target;
-	next_uid(target);
-	crec->addr.cname.uid = target->uid;
-	crec->uid = UID_NONE;
-	cache_hash(crec);
-	make_non_terminals(crec);
-	
-	add_hosts_cname(crec); /* handle chains */
-      }
-}
-  
 static void add_hosts_entry(struct crec *cache, union all_addr *addr, int addrlen, 
 			    unsigned int index, struct crec **rhash, int hashsz)
 {
   struct crec *lookup = cache_find_by_name(NULL, cache_get_name(cache), 0, cache->flags & (F_IPV4 | F_IPV6));
-  int i, nameexists = 0;
+  int i;
   unsigned int j; 
 
   /* Remove duplicates in hosts files. */
-  if (lookup && (lookup->flags & F_HOSTS))
+  if (lookup && (lookup->flags & F_HOSTS) && memcmp(&lookup->addr, addr, addrlen) == 0)
-    {
-      nameexists = 1;
-      if (memcmp(&lookup->addr, addr, addrlen) == 0)
     {
       free(cache);
       return;
     }
-    }
     
   /* Ensure there is only one address -> name mapping (first one trumps) 
      We do this by steam here, The entries are kept in hash chains, linked
@@ -1048,10 +1020,6 @@ static void add_hosts_entry(struct crec *cache, union all_addr *addr, int addrle
   memcpy(&cache->addr, addr, addrlen);  
   cache_hash(cache);
   make_non_terminals(cache);
-  
-  /* don't need to do alias stuff for second and subsequent addresses. */
-  if (!nameexists)
-    add_hosts_cname(cache);
 }
 
 static int eatspace(FILE *f)
@@ -1211,7 +1179,6 @@ void cache_reload(void)
   struct host_record *hr;
   struct name_list *nl;
   struct cname *a;
-  struct interface_name *intr;
 #ifdef HAVE_DNSSEC
   struct ds_config *ds;
 #endif
@@ -1244,22 +1211,19 @@ void cache_reload(void)
 	  up = &cache->hash_next;
       }
   
-  /* Add CNAMEs to interface_names to the cache */
+  /* Add locally-configured CNAMEs to the cache */
   for (a = daemon->cnames; a; a = a->next)
-    for (intr = daemon->int_names; intr; intr = intr->next)
     if (a->alias[1] != '*' &&
-	  hostname_isequal(a->target, intr->name) &&
 	((cache = whine_malloc(SIZEOF_POINTER_CREC))))
       {
 	cache->flags = F_FORWARD | F_NAMEP | F_CNAME | F_IMMORTAL | F_CONFIG;
 	cache->ttd = a->ttl;
 	cache->name.namep = a->alias;
-	  cache->addr.cname.target.int_name = intr;
+	cache->addr.cname.target.name = a->target;
-	  cache->addr.cname.uid = SRC_INTERFACE;
+	cache->addr.cname.uid = SRC_PTR;
 	cache->uid = UID_NONE;
 	cache_hash(cache);
 	make_non_terminals(cache);
-	  add_hosts_cname(cache); /* handle chains */
       }
   
 #ifdef HAVE_DNSSEC
@@ -1364,39 +1328,6 @@ void cache_unhash_dhcp(void)
 	up = &cache->hash_next;
 }
 
-static void add_dhcp_cname(struct crec *target, time_t ttd)
-{
-  struct crec *aliasc;
-  struct cname *a;
-  
-  for (a = daemon->cnames; a; a = a->next)
-    if (a->alias[1] != '*' &&
-	hostname_isequal(cache_get_name(target), a->target))
-      {
-	if ((aliasc = dhcp_spare))
-	  dhcp_spare = dhcp_spare->next;
-	else /* need new one */
-	  aliasc = whine_malloc(SIZEOF_POINTER_CREC);
-	
-	if (aliasc)
-	  {
-	    aliasc->flags = F_FORWARD | F_NAMEP | F_DHCP | F_CNAME | F_CONFIG;
-	    if (ttd == 0)
-	      aliasc->flags |= F_IMMORTAL;
-	    else
-	      aliasc->ttd = ttd;
-	    aliasc->name.namep = a->alias;
-	    aliasc->addr.cname.target.cache = target;
-	    next_uid(target);
-	    aliasc->addr.cname.uid = target->uid;
-	    aliasc->uid = UID_NONE;
-	    cache_hash(aliasc);
-	    make_non_terminals(aliasc);
-	    add_dhcp_cname(aliasc, ttd);
-	  }
-      }
-}
-
 void cache_add_dhcp_entry(char *host_name, int prot,
 			  union all_addr *host_address, time_t ttd) 
 {
@@ -1479,8 +1410,6 @@ void cache_add_dhcp_entry(char *host_name, int prot,
       crec->uid = UID_NONE;
       cache_hash(crec);
       make_non_terminals(crec);
-
-      add_dhcp_cname(crec, ttd);
     }
 }
 #endif

src/dnsmasq.h

@@ -287,9 +287,9 @@ union all_addr {
   struct {
     union {
       struct crec *cache;
-      struct interface_name *int_name;
+      char *name;
     } target;
-    unsigned int uid; /* 0 if union is interface-name */
+    unsigned int uid; /* 0 if union is char * */
   } cname;
   struct {
     struct blockdata *keydata;
@@ -483,10 +483,10 @@ struct crec {
 
 #define UID_NONE      0
 /* Values of uid in crecs with F_CONFIG bit set. */
-/* cname to uid SRC_INTERFACE are to interface names,
+/* cname to uid SRC_PTR are to locally-configured CNAME
-   so use UID_NONE for that to eliminate clashes with
+   so use UID_NONE for that to 
-   any other uid */
+   eliminate clashes with any other uid */
-#define SRC_INTERFACE UID_NONE
+#define SRC_PTR UID_NONE
 #define SRC_CONFIG    1
 #define SRC_HOSTS     2
 #define SRC_AH        3

src/rfc1035.c

@@ -788,7 +788,7 @@ int extract_addresses(struct dns_header *header, size_t qlen, char *name, time_t
 		      if (newc)
 			{
 			  newc->addr.cname.target.cache = NULL;
-			  /* anything other than zero, to avoid being mistaken for CNAME to interface-name */ 
+			  /* anything other than zero, to avoid being mistaken for a local CNAME */ 
 			  newc->addr.cname.uid = 1; 
 			  if (cpp)
 			    {