all: remove using tcp scheme in config and documentation

Using TCP for parent name server is discouraged, because most of server
disallow keeping the connection alive.

The valid use case for TCP connection is when server received truncated
UDP answer.

Using UDP as parent scheme, will automatically assume that the server
also capable of handling query in TCP.
This is required when client (for example, your browser) re-send the query
after receiving truncated UDP answer.
Any query received by rescached through TCP will forwarded to the parent
name server as TCP too, using the same address and port defined in one of
UDP parent.

While at it, use Cloudflare DNS server as default in configuration
and as example in documentation.

3 files changed, 22 insertions, 14 deletions

diff --git a/_doc/rescached.cfg.5.gz b/_doc/rescached.cfg.5.gz
index da08b6e..a5dbbea 100644
--- a/_doc/rescached.cfg.5.gz
+++ b/_doc/rescached.cfg.5.gz
diff --git a/_doc/rescached.cfg.adoc b/_doc/rescached.cfg.adoc
index f8739d3..8ca017a 100644
--- a/_doc/rescached.cfg.adoc
+++ b/_doc/rescached.cfg.adoc
@@ -50,8 +50,8 @@ Format:: /any/path/to/file
 Default:: /etc/rescached/resolv.conf
 Description:: A path to dynamically generated *resolv.conf*(5) by
 *resolvconf*(8).  If set, the nameserver values in referenced file will
-replace "parent" value and "parent" will become a fallback in
-case the referenced file being deleted or can't be parsed.
+be used as "parent" name server if no "parent" is defined in configuration
+file.
 
 To use this config, you must set either "dnsmasq_resolv", "pdnsd_resolv", or
 "unbound_conf" in "/etc/resolvconf.conf" to point to
@@ -90,22 +90,31 @@ Format::
 
 ----
 parent  = "parent = " [ scheme "://"] ( ip-address / domain-name ) [ ":" port ]
-scheme  = ( "tcp" / "udp" / "https")
+scheme  = ( "udp" / "https")
 ----
 
 Default::
-* Address: udp://35.240.172.103
+* Address: udp://1.1.1.1
 * Port: 53
 Description:: List of parent DNS servers.
 +
-When +rescached+ receive a query from client and when it does
-not have a cached address of query, it will forward the query to those parent
-servers.
+When +rescached+ receive a query from client (for example, your browser) and
+when it does not have a cached answer for that query, it will forward the
+query to one of the parent name servers.
++
+Using UDP as parent scheme, will automatically assume that the server also
+capable of handling query in TCP.
+This is required when client (for example, your browser) re-send the query
+after receiving truncated UDP answer.
+Any query received by +rescached+ through TCP will forwarded to the parent
+name server as TCP too, using the same address and port defined in one of UDP
+parent.
 +
 Please, do not use OpenDNS server.
 If certain host-name not found (i.e. typo in host-name), OpenDNS will reply
 with its own address, instead of replying with empty answer.
-This will make +rescached+ caching a false data.
+This will make +rescached+ caching a false data and it may make your
+application open or consume unintended resources.
 +
 To check if your parent server reply the unknown host-name with no answer, use
 *resolver*(1) tool.
@@ -113,10 +122,10 @@ To check if your parent server reply the unknown host-name with no answer, use
 Example::
 ----
   ## Using UDP connection to forward request to parent name server.
-  parent = udp://35.240.172.103
+  parent = udp://1.1.1.1
 
-  ## Using TCP connection to forward request to parent name server.
-  parent = tcp://35.240.172.103
+  ## Using DNS over TLS to forward request to parent name server.
+  parent = https://1.1.1.1
 
   ## Using DNS over HTTPS to forward request to parent name server.
   parent = https://kilabit.info/dns-query
diff --git a/cmd/rescached/rescached.cfg b/cmd/rescached/rescached.cfg
index 89d5a05..16d6be4 100644
--- a/cmd/rescached/rescached.cfg
+++ b/cmd/rescached/rescached.cfg
@@ -15,10 +15,9 @@ hosts_block = http://winhelp2002.mvps.org/hosts.txt
 hosts_block = http://someonewhocares.org/hosts/hosts
 
 [dns "server"]
-#parent=udp://18.136.35.199
-#parent=tcp://18.136.35.199
+parent=udp://1.1.1.1
 ## DNS over TLS
-parent=https://18.136.35.199
+#parent=https://1.1.1.1
 ## DNS over HTTPS
 #parent=https://kilabit.info/dns-query