From 832e47beab95c2918b5264f0504f2fe6fe523e4c Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Wed, 24 Feb 2016 21:24:45 +0000
Subject: [PATCH] Add --dhcp-ttl option.

---
 man/dnsmasq.8 |  5 ++++-
 src/dnsmasq.h |  2 +-
 src/option.c  | 13 +++++++++++--
 src/rfc1035.c |  2 +-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/man/dnsmasq.8 b/man/dnsmasq.8
index 7bc1394..2bcce20 100644
--- a/man/dnsmasq.8
+++ b/man/dnsmasq.8
@@ -60,7 +60,7 @@ in the same way as for DHCP-derived names. Note that this does not
 apply to domain names in cnames, PTR records, TXT records etc.
 .TP
 .B \-T, --local-ttl=<time>
-When replying with information from /etc/hosts or the DHCP leases
+When replying with information from /etc/hosts or configuration or the DHCP leases
 file dnsmasq by default sets the time-to-live field to zero, meaning
 that the requester should not itself cache the information. This is
 the correct thing to do in almost all situations. This option allows a
@@ -68,6 +68,9 @@ time-to-live (in seconds) to be given for these replies. This will
 reduce the load on the server at the expense of clients using stale
 data under some circumstances.
 .TP
+.B --dhcp-ttl=<time>
+As for --local-ttl, but affects only replies with information from DHCP leases. If both are given, --dhcp-ttl applies for DHCP information, and --local-ttl for others. Setting this to zero eliminates the effect of --local-ttl for DHCP.
+.TP
 .B --neg-ttl=<time>
 Negative replies from upstream servers normally contain time-to-live
 information in SOA records which dnsmasq uses for caching. If the
diff --git a/src/dnsmasq.h b/src/dnsmasq.h
index 6344df5..9f73c3b 100644
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -955,7 +955,7 @@ extern struct daemon {
   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;
+  unsigned long local_ttl, neg_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 --git a/src/option.c b/src/option.c
index 7c5e6bc..3f6d162 100644
--- a/src/option.c
+++ b/src/option.c
@@ -157,6 +157,7 @@ struct myoption {
 #define LOPT_MAXPORT       345
 #define LOPT_CPE_ID        346
 #define LOPT_SCRIPT_ARP    347
+#define LOPT_DHCPTTL       348
 
 #ifdef HAVE_GETOPT_LONG
 static const struct option opts[] =  
@@ -319,6 +320,7 @@ static const struct myoption opts[] =
     { "quiet-ra", 0, 0, LOPT_QUIET_RA },
     { "dns-loop-detect", 0, 0, LOPT_LOOP_DETECT },
     { "script-arp", 0, 0, LOPT_SCRIPT_ARP },
+    { "dhcp-ttl", 1, 0 , LOPT_DHCPTTL },
     { NULL, 0, 0, 0 }
   };
 
@@ -485,9 +487,10 @@ static struct {
   { LOPT_QUIET_DHCP, OPT_QUIET_DHCP, NULL, gettext_noop("Do not log routine DHCP."), NULL },
   { LOPT_QUIET_DHCP6, OPT_QUIET_DHCP6, NULL, gettext_noop("Do not log routine DHCPv6."), NULL },
   { LOPT_QUIET_RA, OPT_QUIET_RA, NULL, gettext_noop("Do not log RA."), NULL },
-  { LOPT_LOCAL_SERVICE, OPT_LOCAL_SERVICE, NULL, gettext_noop("Accept queries only from directly-connected networks"), NULL },
-  { LOPT_LOOP_DETECT, OPT_LOOP_DETECT, NULL, gettext_noop("Detect and remove DNS forwarding loops"), NULL },
+  { LOPT_LOCAL_SERVICE, OPT_LOCAL_SERVICE, NULL, gettext_noop("Accept queries only from directly-connected networks."), NULL },
+  { LOPT_LOOP_DETECT, OPT_LOOP_DETECT, NULL, gettext_noop("Detect and remove DNS forwarding loops."), NULL },
   { LOPT_IGNORE_ADDR, ARG_DUP, "<ipaddr>", gettext_noop("Ignore DNS responses containing ipaddr."), NULL }, 
+  { LOPT_DHCPTTL, ARG_ONE, "<ttl>", gettext_noop("Set TTL in DNS responses with DHCP-derived addresses."), NULL }, 
   { 0, 0, NULL, NULL, NULL }
 }; 
 
@@ -2580,6 +2583,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
     case LOPT_MINCTTL: /* --min-cache-ttl */
     case LOPT_MAXCTTL: /* --max-cache-ttl */
     case LOPT_AUTHTTL: /* --auth-ttl */
+    case LOPT_DHCPTTL: /* --dhcp-ttl */
       {
 	int ttl;
 	if (!atoi_check(arg, &ttl))
@@ -2598,6 +2602,11 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 	  daemon->max_cache_ttl = (unsigned long)ttl;
 	else if (option == LOPT_AUTHTTL)
 	  daemon->auth_ttl = (unsigned long)ttl;
+	else if (option == LOPT_DHCPTTL)
+	  {
+	    daemon->dhcp_ttl = (unsigned long)ttl;
+	    daemon->use_dhcp_ttl = 1;
+	  }
 	else
 	  daemon->local_ttl = (unsigned long)ttl;
 	break;
diff --git a/src/rfc1035.c b/src/rfc1035.c
index 3535a71..8f1e3b4 100644
--- a/src/rfc1035.c
+++ b/src/rfc1035.c
@@ -1170,7 +1170,7 @@ static unsigned long crec_ttl(struct crec *crecp, time_t now)
      before the lease expires. */
 
   if (crecp->flags & F_DHCP)
-    return daemon->local_ttl;
+    return daemon->use_dhcp_ttl ? daemon->dhcp_ttl : daemon->local_ttl;
   
   /* Immortal entries other than DHCP are local, and hold TTL in TTD field. */
   if (crecp->flags & F_IMMORTAL)