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虽然dnsmasq自带参数min-cache-ttl可修改服务器缓存最小值，但是首次请求返回给客户端的时正常ttl，使用以下patch可修改返回给客户端ttl时间，配合min-cache-ttl保持和dnsmasq缓存ttl时间一致，dnsmasq不开启缓存可单独修改min ttl。
适用于dnsmasq2.80版本，

diff -urN dnsmasq-2.80/src/dnsmasq.h dnsmasq-2.80-bak/src/dnsmasq.h
--- dnsmasq-2.80/src/dnsmasq.h  2018-10-19 02:21:55.000000000 +0800
+++ dnsmasq-2.80-bak/src/dnsmasq.h      2020-01-13 10:38:16.940067371 +0800
@@ -1023,7 +1023,7 @@
   int max_logs;  /* queue limit */
   int cachesize, ftabsize;
   int port, query_port, min_port, max_port;
-  unsigned long local_ttl, neg_ttl, max_ttl, min_cache_ttl, max_cache_ttl, auth_ttl, dhcp_ttl, use_dhcp_ttl;
+  unsigned long local_ttl, neg_ttl, min_ttl, max_ttl, min_cache_ttl, max_cache_ttl, auth_ttl, dhcp_ttl, use_dhcp_ttl;
   char *dns_client_id;
   struct hostsfile *addn_hosts;
   struct dhcp_context *dhcp, *dhcp6;
diff -urN dnsmasq-2.80/src/option.c dnsmasq-2.80-bak/src/option.c
--- dnsmasq-2.80/src/option.c   2018-10-19 02:21:55.000000000 +0800
+++ dnsmasq-2.80-bak/src/option.c       2020-01-13 17:21:13.925164926 +0800
@@ -106,6 +106,7 @@
 #define LOPT_PROXY         295
 #define LOPT_GEN_NAMES     296
 #define LOPT_MAXTTL        297
+#define LOPT_MINTTL        397
 #define LOPT_NO_REBIND     298
 #define LOPT_LOC_REBND     299
 #define LOPT_ADD_MAC       300
@@ -281,6 +282,7 @@
     { "dhcp-broadcast", 2, 0, LOPT_BROADCAST },
     { "neg-ttl", 1, 0, LOPT_NEGTTL },
     { "max-ttl", 1, 0, LOPT_MAXTTL },
+    { "min-ttl", 1, 0, LOPT_MINTTL },
     { "min-cache-ttl", 1, 0, LOPT_MINCTTL },
     { "max-cache-ttl", 1, 0, LOPT_MAXCTTL },
     { "dhcp-alternate-port", 2, 0, LOPT_ALTPORT },
@@ -409,6 +411,7 @@
   { '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_MINTTL, ARG_ONE, "<integer>", gettext_noop("Specify time-to-live in seconds for minimum 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 }, 
@@ -2664,6 +2667,7 @@
     case 'T':         /* --local-ttl */
     case LOPT_NEGTTL: /* --neg-ttl */
     case LOPT_MAXTTL: /* --max-ttl */
+    case LOPT_MINTTL: /* --min-ttl */
     case LOPT_MINCTTL: /* --min-cache-ttl */
     case LOPT_MAXCTTL: /* --max-cache-ttl */
     case LOPT_AUTHTTL: /* --auth-ttl */
@@ -2676,6 +2680,8 @@
          daemon->neg_ttl = (unsigned long)ttl;
        else if (option == LOPT_MAXTTL)
          daemon->max_ttl = (unsigned long)ttl;
+       else if (option == LOPT_MINTTL)
+         daemon->min_ttl = (unsigned long)ttl;
        else if (option == LOPT_MINCTTL)
          {
            if (ttl > TTL_FLOOR_LIMIT)
diff -urN dnsmasq-2.80/src/rfc1035.c dnsmasq-2.80-bak/src/rfc1035.c
--- dnsmasq-2.80/src/rfc1035.c  2018-10-19 02:21:55.000000000 +0800
+++ dnsmasq-2.80-bak/src/rfc1035.c      2020-01-13 17:12:25.455445871 +0800
@@ -669,11 +669,20 @@
                  GETSHORT(aqtype, p1); 
                  GETSHORT(aqclass, p1);
                  GETLONG(attl, p1);
+                  unsigned long mttl = 0;
                  if ((daemon->max_ttl != 0) && (attl > daemon->max_ttl) && !is_sign)
                    {
-                     (p1) -= 4;
-                     PUTLONG(daemon->max_ttl, p1);
+                      mttl = daemon->max_ttl;
+                   }
+                 if ((daemon->min_ttl != 0) && (attl < daemon->min_ttl) && !is_sign)
+                   {
+                      mttl = daemon->min_ttl;
                    }
+                  if (mttl != 0)
+                  {
+                     (p1) -= 4;
+                     PUTLONG(mttl, p1);
+                  }
                  GETSHORT(ardlen, p1);
                  endrr = p1+ardlen;
                  
@@ -762,11 +771,20 @@
              GETSHORT(aqtype, p1); 
              GETSHORT(aqclass, p1);
              GETLONG(attl, p1);
+              unsigned long mttl = 0;
              if ((daemon->max_ttl != 0) && (attl > daemon->max_ttl) && !is_sign)
-               {
-                 (p1) -= 4;
-                 PUTLONG(daemon->max_ttl, p1);
-               }
+               {
+                  mttl = daemon->max_ttl;
+               }
+             if ((daemon->min_ttl != 0) && (attl < daemon->min_ttl) && !is_sign)
+               {
+                  mttl = daemon->min_ttl;
+               }
+              if (mttl != 0)
+              {
+                 (p1) -= 4;
+                 PUTLONG(mttl, p1);
+              }
              GETSHORT(ardlen, p1);
              endrr = p1+ardlen;
              

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