Add --min-cache-ttl option.

CHANGELOG

@@ -43,6 +43,13 @@ version 2.73
 	    Add --log-queries=extra option, which makes logs easier
 	    to search automatically.
 
+	    Add --min-cache-ttl option. I've resisted this for a long 
+	    time, on the grounds that disbelieving TTLs is never a 
+	    good idea, but I've been persuaded that there are 
+	    sometimes reasons to do it. (Step forward, GFW).
+	    To avoid misuse, there's a hard limit on the TTL 
+	    floor of one hour. Thansk to RinSatsuki for the patch.
+	
 	
 version 2.72
             Add ra-advrouter mode, for RFC-3775 mobile IPv6 support.

man/dnsmasq.8

@@ -81,6 +81,12 @@ the upstream DNS servers.
 .B --max-cache-ttl=<time>
 Set a maximum TTL value for entries in the cache.
 .TP
+.B --min-cache-ttl=<time>
+Extend short TTL values to the time given when caching them. Note that
+artificially extending TTL values is in general a bad idea, do not do it 
+unless you have a good reason, and understand what you are doing. 
+Dnsmasq limits the value of this option to one hour, unless recompiled.
+.TP
 .B --auth-ttl=<time>
 Set the TTL value returned in answers from the authoritative server.
 .TP

src/cache.c

@@ -461,9 +461,11 @@ struct crec *cache_insert(char *name, struct all_addr *addr,
   if (flags & (F_IPV4 | F_IPV6 | F_CNAME))
     {
       log_query(flags | F_UPSTREAM, name, addr, NULL);
-      /* Don;t mess with TTL for DNSSEC records. */
+      /* Don't mess with TTL for DNSSEC records. */
       if (daemon->max_cache_ttl != 0 && daemon->max_cache_ttl < ttl)
 	ttl = daemon->max_cache_ttl;
+      if (daemon->min_cache_ttl != 0 && daemon->min_cache_ttl > ttl)
+	ttl = daemon->min_cache_ttl;
     }
 
   /* if previous insertion failed give up now. */

src/config.h

@@ -27,6 +27,7 @@
 #define RANDOM_SOCKS 64 /* max simultaneous random ports */
 #define LEASE_RETRY 60 /* on error, retry writing leasefile after LEASE_RETRY seconds */
 #define CACHESIZ 150 /* default cache size */
+#define TTL_FLOOR_LIMIT 3600 /* don't allow --min-cache-ttl to raise TTL above this under any circumstances */
 #define MAXLEASES 1000 /* maximum number of DHCP leases */
 #define PING_WAIT 3 /* wait for ping address-in-use test */
 #define PING_CACHE_TIME 30 /* Ping test assumed to be valid this long. */

src/dnsmasq.h

@@ -943,7 +943,7 @@ extern struct daemon {
   int max_logs;  /* queue limit */
   int cachesize, ftabsize;
   int port, query_port, min_port;
-  unsigned long local_ttl, neg_ttl, max_ttl, max_cache_ttl, auth_ttl;
+  unsigned long local_ttl, neg_ttl, max_ttl, min_cache_ttl, max_cache_ttl, auth_ttl;
   struct hostsfile *addn_hosts;
   struct dhcp_context *dhcp, *dhcp6;
   struct ra_interface *ra_interfaces;

src/option.c

@@ -148,6 +148,7 @@ struct myoption {
 #define LOPT_DNSSEC_TIME   336
 #define LOPT_LOOP_DETECT   337
 #define LOPT_IGNORE_ADDR   338
+#define LOPT_MINCTTL       339
 
 
 #ifdef HAVE_GETOPT_LONG
@@ -256,6 +257,7 @@ static const struct myoption opts[] =
     { "dhcp-broadcast", 2, 0, LOPT_BROADCAST },
     { "neg-ttl", 1, 0, LOPT_NEGTTL },
     { "max-ttl", 1, 0, LOPT_MAXTTL },
+    { "min-cache-ttl", 1, 0, LOPT_MINCTTL },
     { "max-cache-ttl", 1, 0, LOPT_MAXCTTL },
     { "dhcp-alternate-port", 2, 0, LOPT_ALTPORT },
     { "dhcp-scriptuser", 1, 0, LOPT_SCRIPTUSR },
@@ -371,6 +373,8 @@ static struct {
   { 'T', ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in seconds for replies from /etc/hosts."), NULL },
   { LOPT_NEGTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in seconds for negative caching."), NULL },
   { LOPT_MAXTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in seconds for maximum TTL to send to clients."), NULL },
+  { LOPT_MAXCTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live ceiling for cache."), NULL },
+  { LOPT_MINCTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live floor for cache."), NULL },
   { 'u', ARG_ONE, "<username>", gettext_noop("Change to this user after startup. (defaults to %s)."), CHUSER }, 
   { 'U', ARG_DUP, "set:<tag>,<class>", gettext_noop("Map DHCP vendor class to tag."), NULL },
   { 'v', 0, NULL, gettext_noop("Display dnsmasq version and copyright information."), NULL },
@@ -2457,6 +2461,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
     case 'T':         /* --local-ttl */
     case LOPT_NEGTTL: /* --neg-ttl */
     case LOPT_MAXTTL: /* --max-ttl */
+    case LOPT_MINCTTL: /* --min-cache-ttl */
     case LOPT_MAXCTTL: /* --max-cache-ttl */
     case LOPT_AUTHTTL: /* --auth-ttl */
       {
@@ -2467,6 +2472,12 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 	  daemon->neg_ttl = (unsigned long)ttl;
 	else if (option == LOPT_MAXTTL)
 	  daemon->max_ttl = (unsigned long)ttl;
+	else if (option == LOPT_MINCTTL)
+	  {
+	    if (ttl > TTL_FLOOR_LIMIT)
+	      ttl = TTL_FLOOR_LIMIT;
+	    daemon->min_cache_ttl = (unsigned long)ttl;
+	  }
 	else if (option == LOPT_MAXCTTL)
 	  daemon->max_cache_ttl = (unsigned long)ttl;
 	else if (option == LOPT_AUTHTTL)