opts: Add option to disable DNS lookups

Mainly used to disable `gossipd` reaching out to the DNS seeds during testing.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

doc/lightningd-config.5

@@ -2,12 +2,12 @@
 .\"     Title: lightningd-config
 .\"    Author: [see the "AUTHOR" section]
 .\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
-.\"      Date: 05/10/2018
+.\"      Date: 06/20/2018
 .\"    Manual: \ \&
 .\"    Source: \ \&
 .\"  Language: English
 .\"
-.TH "LIGHTNINGD\-CONFIG" "5" "05/10/2018" "\ \&" "\ \&"
+.TH "LIGHTNINGD\-CONFIG" "5" "06/20/2018" "\ \&" "\ \&"
 .\" -----------------------------------------------------------------
 .\" * Define some portability stuff
 .\" -----------------------------------------------------------------
@@ -203,14 +203,16 @@ How long to wait before sending commitment messages to the peer: in theory incre
 .sp
 Lightning channel and HTLC options:
 .PP
-\fBlocktime\-blocks\fR=\fIBLOCKS\fR
+\fBwatchtime\-blocks\fR=\fIBLOCKS\fR
 .RS 4
-How long we need to spot an outdated close attempt, which is also how long the peer would need to wait if they perform a unilateral close\&.
+How long we need to spot an outdated close attempt: on opening a channel we tell our peer that this is how long they\(cqll have to wait if they perform a unilateral close\&.
 .RE
 .PP
 \fBmax\-locktime\-blocks\fR=\fIBLOCKS\fR
 .RS 4
-The longest we\(cqll ever allow a peer to hold up payments, in the worst case\&. If they ask for longer, we\(cqll refuse to create a channel, and if an HTLC asks for longer, we\(cqll refuse it\&.
+The longest our funds can be delayed (ie\&. the longest
+\fBwatchtime\-blocks\fR
+our peer can ask for, and also the longest HTLC timeout we will accept)\&. If our peer asks for longer, we\(cqll refuse to create a channel, and if an HTLC asks for longer, we\(cqll refuse it\&.
 .RE
 .PP
 \fBfunding\-confirms\fR=\fIBLOCKS\fR
@@ -408,6 +410,11 @@ Always use the
 \fBproxy\fR, even to connect to normal IP addresses (you can still connect to Unix domain sockets manually)\&. This also disables all DNS lookups, to avoid leaking information\&.
 .RE
 .PP
+\fBdisable\-dns\fR
+.RS 4
+Disable the DNS bootstrapping mechanism to find a node by its node ID\&.
+.RE
+.PP
 \fBtor\-service\-password\fR=\fIPASSWORD\fR
 .RS 4
 Set a Tor control password, which may be needed for

doc/lightningd-config.5.txt

@@ -100,7 +100,7 @@ Lightning daemon options:
 
 *pid-file*='PATH'::
     Specify pid file to write to.
-  
+
 *log-level*='LEVEL'::
     What log level to print out: options are io, debug, info, unusual, broken.
 
@@ -278,10 +278,13 @@ or precisely control where to bind and what to announce with the
     can still connect to Unix domain sockets manually).  This also disables
     all DNS lookups, to avoid leaking information.
 
+*disable-dns*::
+    Disable the DNS bootstrapping mechanism to find a node by its node ID.
+
 *tor-service-password*='PASSWORD'::
     Set a Tor control password, which may be needed for 'autotor:' to
     authenticate to the Tor control port.
-    
+
 BUGS
 ----
 You should report bugs on our github issues page, and maybe submit a

lightningd/lightningd.h

@@ -64,6 +64,9 @@ struct config {
 	/* Accept fee changes only if they are in the range our_fee -
 	 * our_fee*multiplier */
 	u32 max_fee_multiplier;
+
+	/* Are we allowed to use DNS lookup for peers. */
+	bool use_dns;
 };
 
 struct lightningd {

lightningd/options.c

@@ -409,6 +409,9 @@ static void config_register_opts(struct lightningd *ld)
 			       opt_set_bool_arg, opt_show_bool,
 			       &ld->use_proxy_always, "Use the proxy always");
 
+	opt_register_noarg("--disable-dns", opt_set_invbool, &ld->config.use_dns,
+			   "Disable DNS lookups of peers");
+
 #if DEVELOPER
 	opt_register_arg("--dev-max-funding-unconfirmed-blocks",
 			 opt_set_u32, opt_show_u32,
@@ -529,6 +532,8 @@ static const struct config testnet_config = {
 
 	/* Fees may be in the range our_fee - 10*our_fee */
 	.max_fee_multiplier = 10,
+
+	.use_dns = true,
 };
 
 /* aka. "Dude, where's my coins?" */
@@ -590,6 +595,8 @@ static const struct config mainnet_config = {
 
 	/* Fees may be in the range our_fee - 10*our_fee */
 	.max_fee_multiplier = 10,
+
+	.use_dns = true,
 };
 
 static void check_config(struct lightningd *ld)