From 6d82f29f090d36d2f3d7191e16c0a10f025af366 Mon Sep 17 00:00:00 2001
From: DL6ER <dl6er@dl6er.de>
Date: Sun, 22 Apr 2018 12:08:44 +0200
Subject: [PATCH] Add BLOCKINGMODE=IP|NXDOMAIN config flag for selecting if
 FTLDNS should reply with IPv4/IPv6 addresses (need 2 cache slots per domain)
 or with NXDOMAIN (need 1 cache slot per domain)

Signed-off-by: DL6ER <dl6er@dl6er.de>
---
 FTL.h               |  2 ++
 README.md           |  1 +
 config.c            | 21 +++++++++++++++++++++
 dnsmasq_interface.c | 10 +++++++---
 4 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/FTL.h b/FTL.h
index 30d96646..8569e695 100644
--- a/FTL.h
+++ b/FTL.h
@@ -132,6 +132,7 @@ typedef struct {
 	int maxlogage;
 	int privacylevel;
 	bool ignore_localhost;
+	unsigned char blockingmode;
 } ConfigStruct;
 
 // Dynamic structs
@@ -212,6 +213,7 @@ enum { QUERY_UNKNOWN, QUERY_GRAVITY, QUERY_FORWARDED, QUERY_CACHE, QUERY_WILDCAR
 enum { TYPE_A = 1, TYPE_AAAA, TYPE_ANY, TYPE_SRV, TYPE_SOA, TYPE_PTR, TYPE_TXT, TYPE_MAX };
 enum { REPLY_UNKNOWN, REPLY_NODATA, REPLY_NXDOMAIN, REPLY_CNAME, REPLY_IP };
 enum { PRIVACY_SHOW_ALL = 0, PRIVACY_HIDE_DOMAINS, PRIVACY_HIDE_DOMAINS_CLIENTS, PRIVACY_MAXIMUM };
+enum { MODE_IP, MODE_NX };
 
 // Used to check memory integrity in various structs
 #define MAGICBYTE 0x57
diff --git a/README.md b/README.md
index 11ec74ed..8d0e0d62 100644
--- a/README.md
+++ b/README.md
@@ -168,6 +168,7 @@ Possible settings (**the option shown first is the default**):
 - `FTLPORT=4711` (On which port should FTL be listening?)
 - `PRIVACYLEVEL=0` (Which privacy level is used? Can be 0 (permissive) to 3 (very restrictive), see below)
 - `IGNORE_LOCALHOST=no|yes` (Should `FTL` ignore queries coming from the local machine?)
+- `BLOCKINGMODE=IP|NXDOMAIN` (Should `FTL` reply queries to blocked domains with IPs or NXDOMAIN?)
 
 ### Privacy levels
 Specifies if we want to anonymize the DNS queries somehow, available options are:
diff --git a/config.c b/config.c
index 94f53dbe..3bb6c02e 100644
--- a/config.c
+++ b/config.c
@@ -187,6 +187,27 @@ void read_FTLconf(void)
 	else
 		logg("   IGNORE_LOCALHOST: Show queries from localhost");
 
+	// BLOCKINGMODE
+	// defaults to: MODE_IP
+	config.blockingmode = MODE_IP;
+	buffer = parse_FTLconf(fp, "BLOCKINGMODE");
+
+	if(buffer != NULL)
+	{
+		if(strcasecmp(buffer, "NXDOMAIN") == 0)
+			config.blockingmode = MODE_NX;
+	}
+
+	switch(config.blockingmode)
+	{
+		case MODE_NX:
+			logg("   BLOCKINGMODE: NXDOMAIN for blocked domains");
+			break;
+		default:
+			logg("   BLOCKINGMODE: Pi-hole's IP for blocked domains");
+			break;
+	}
+
 	logg("Finished config file parsing");
 
 	// Release memory
diff --git a/dnsmasq_interface.c b/dnsmasq_interface.c
index 97b96f6d..518ddd20 100644
--- a/dnsmasq_interface.c
+++ b/dnsmasq_interface.c
@@ -500,6 +500,8 @@ void FTL_cache(unsigned int flags, char *name, struct all_addr *addr, char *arg,
 				requesttype = QUERY_GRAVITY;
 			else if(arg != NULL && strstr(arg, "/black.list") != NULL)
 				requesttype = QUERY_BLACKLIST;
+			else if(flags & F_NXDOMAIN)
+				requesttype = QUERY_GRAVITY;
 			else // local.list, hostname.list, /etc/hosts and others
 				requesttype = QUERY_CACHE;
 		}
@@ -846,20 +848,22 @@ int FTL_listsfile(char* filename, unsigned int index, FILE *f, int cache_size, s
 		{
 			strcpy(cache4->name.sname, domain);
 			cache4->flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV4;
+			if(config.blockingmode == MODE_NX) cache4->flags |= F_NEG | F_NXDOMAIN;
 			cache4->ttd = daemon->local_ttl;
 			add_hosts_entry(cache4, &addr4, INADDRSZ, index, rhash, hashsz);
+			name_count++;
 		}
-		// Add IPv6 record
-		if ((cache6 = malloc(sizeof(struct crec) + strlen(domain)+1-SMALLDNAME)))
+		// Add IPv6 record only if we respond with an IP address to blocked domains
+		if (config.blockingmode == MODE_IP && (cache6 = malloc(sizeof(struct crec) + strlen(domain)+1-SMALLDNAME)))
 		{
 			strcpy(cache6->name.sname, domain);
 			cache6->flags = F_HOSTS | F_IMMORTAL | F_FORWARD | F_REVERSE | F_IPV6;
 			cache6->ttd = daemon->local_ttl;
 			add_hosts_entry(cache6, &addr6, IN6ADDRSZ, index, rhash, hashsz);
+			name_count++;
 		}
 
 		added++;
-		name_count++;
 	}
 
 	// Free allocated memory