Add --no-round-robin option.

CHANGELOG

@@ -32,7 +32,9 @@ version 2.88
 	to an easily reproducible case which saved mucg labour in
 	finding it.
 
+	Add --no-round-robin option.
 
+	
 version 2.87
         Allow arbitrary prefix lengths in --rev-server and
 	--domain=....,local

man/dnsmasq.8

@@ -816,6 +816,12 @@ Disable negative caching. Negative caching allows dnsmasq to remember
 "no such domain" answers from upstream nameservers and answer
 identical queries without forwarding them again. 
 .TP
+.B --no-round-robin
+Dnsmasq normally permutes the order of A or AAAA records for the same
+name on successive queries, for load-balancing. This turns off that
+behaviour, so that the records are always returned in the order
+that they are received from upstream.
+.TP
 .B --use-stale-cache
 When set, if a DNS name exists in the cache, but its time-to-live has expired, dnsmasq will return the data anyway. (It attempts to refresh the
 data with an upstream query after returning the stale data.) This can improve speed and reliability. It comes at the expense

src/cache.c

@@ -233,7 +233,8 @@ static void cache_hash(struct crec *crecp)
      immortal entries are at the end of the hash-chain.
      This allows reverse searches and garbage collection to be optimised */
 
-  struct crec **up = hash_bucket(cache_get_name(crecp));
+  char *name = cache_get_name(crecp);
+  struct crec **up = hash_bucket(name);
 
   if (!(crecp->flags & F_REVERSE))
     {
@@ -244,6 +245,11 @@ static void cache_hash(struct crec *crecp)
 	while (*up && !((*up)->flags & F_IMMORTAL))
 	  up = &((*up)->hash_next);
     }
+
+  /* Preserve order when inserting the same name multiple times. */
+  while (*up && hostname_isequal(cache_get_name(*up), name))
+    up = &((*up)->hash_next);
+  
   crecp->hash_next = *up;
   *up = crecp;
 }
@@ -722,7 +728,7 @@ static struct crec *really_insert(char *name, union all_addr *addr, unsigned sho
   new->ttd = now + (time_t)ttl;
   new->next = new_chain;
   new_chain = new;
-
+  
   return new;
 }
 
@@ -900,7 +906,7 @@ int cache_find_non_terminal(char *name, time_t now)
 struct crec *cache_find_by_name(struct crec *crecp, char *name, time_t now, unsigned int prot)
 {
   struct crec *ans;
-  int no_rr = prot & F_NO_RR;
+  int no_rr = (prot & F_NO_RR) || option_bool(OPT_NORR);
 
   prot &= ~F_NO_RR;
   

src/dnsmasq.h

@@ -280,7 +280,8 @@ struct event_desc {
 #define OPT_STRIP_ECS      69
 #define OPT_STRIP_MAC      70
 #define OPT_STALE_CACHE    71
-#define OPT_LAST           72
+#define OPT_NORR           72
+#define OPT_LAST           73
 
 #define OPTION_BITS (sizeof(unsigned int)*8)
 #define OPTION_SIZE ( (OPT_LAST/OPTION_BITS)+((OPT_LAST%OPTION_BITS)!=0) )

src/option.c

@@ -184,6 +184,7 @@ struct myoption {
 #define LOPT_RANDPORT_LIM  375
 #define LOPT_FAST_RETRY    376
 #define LOPT_STALE_CACHE   377
+#define LOPT_NORR          378
 
 #ifdef HAVE_GETOPT_LONG
 static const struct option opts[] =  
@@ -236,6 +237,7 @@ static const struct myoption opts[] =
     { "localmx", 0, 0, 'L' },
     { "local-ttl", 1, 0, 'T' },
     { "no-negcache", 0, 0, 'N' },
+    { "no-round-robin", 0, 0, LOPT_NORR },
     { "addn-hosts", 1, 0, 'H' },
     { "hostsdir", 1, 0, LOPT_HOST_INOTIFY },
     { "query-port", 1, 0, 'Q' },
@@ -567,6 +569,7 @@ static struct {
   { LOPT_SCRIPT_TIME, OPT_LEASE_RENEW, NULL, gettext_noop("Call dhcp-script when lease expiry changes."), NULL },
   { LOPT_UMBRELLA, ARG_ONE, "[=<optspec>]", gettext_noop("Send Cisco Umbrella identifiers including remote IP."), NULL },
   { LOPT_QUIET_TFTP, OPT_QUIET_TFTP, NULL, gettext_noop("Do not log routine TFTP."), NULL },
+  { LOPT_NORR, OPT_NORR, NULL, gettext_noop("Suppress round-robin ordering of DNS records."), NULL },
   { 0, 0, NULL, NULL, NULL }
 };