From: Grigorii Demidov <grigorii.demidov@nic.cz>
Date: Tue, 13 Nov 2018 10:48:31 +0000 (+0100)
Subject: modules/edns_keepalive: new module, loaded by default
X-Git-Tag: v3.2.0~37^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=65d1c322df78b123403fc6273f58923d8329d31f;p=thirdparty%2Fknot-resolver.git

modules/edns_keepalive: new module, loaded by default

Minor changes to be blamed on Vladimir.
---

diff --git a/NEWS b/NEWS
index e830f6bc0..b2e9b342f 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,10 @@
 Knot Resolver 3.x.y (201y-mm-dd)
 ================================
 
+New features
+------------
+- module edns_keepalive to implement server side of RFC 7828 (#408)
+
 Module API changes
 ------------------
 - new layer is added: answer_finalize
diff --git a/daemon/lua/sandbox.lua b/daemon/lua/sandbox.lua
index f10d5a777..017e3a399 100644
--- a/daemon/lua/sandbox.lua
+++ b/daemon/lua/sandbox.lua
@@ -322,6 +322,7 @@ modules.load('priming')
 modules.load('detect_time_skew')
 modules.load('detect_time_jump')
 modules.load('ta_sentinel')
+modules.load('edns_keepalive')
 
 -- Interactive command evaluation
 function eval_cmd(line, raw)
diff --git a/doc/modules.rst b/doc/modules.rst
index 8ddf54daf..cb350b336 100644
--- a/doc/modules.rst
+++ b/doc/modules.rst
@@ -32,3 +32,4 @@ Knot Resolver modules
 .. include:: ../modules/rfc7706.rst
 .. include:: ../modules/prefill/README.rst
 .. include:: ../modules/serve_stale/README.rst
+.. include:: ../modules/edns_keepalive/README.rst
diff --git a/modules/edns_keepalive/README.rst b/modules/edns_keepalive/README.rst
new file mode 100644
index 000000000..7938632b9
--- /dev/null
+++ b/modules/edns_keepalive/README.rst
@@ -0,0 +1,12 @@
+.. _mod-edns_keepalive:
+
+EDNS keepalive
+--------------
+
+The ``edns_keepalive`` module implements :rfc:`7828` for *clients* connecting to Knot Resolver via TCP and TLS.
+Note that client connections are timed-out the same way *regardless* of them sending the EDNS option;
+the module just allows clients to discover the timeout.
+
+When connecting to servers, Knot Resolver does not send this EDNS option.
+It still attempts to reuse established connections intelligently.
+
diff --git a/modules/edns_keepalive/edns_keepalive.c b/modules/edns_keepalive/edns_keepalive.c
new file mode 100644
index 000000000..e9676c0b9
--- /dev/null
+++ b/modules/edns_keepalive/edns_keepalive.c
@@ -0,0 +1,77 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file edns_keepalive.c
+ * @brief Minimalistic EDNS keepalive implementation on server side.
+ *        If keepalive option is present in query,
+ *        always reply with constant timeout value.
+ *
+ */
+#include <libknot/packet/pkt.h>
+#include "daemon/worker.h"
+#include "lib/module.h"
+#include "lib/layer.h"
+
+static int edns_keepalive_finalize(kr_layer_t *ctx)
+{
+	struct kr_request *req = ctx->req;
+	knot_pkt_t *answer = req->answer;
+	const knot_rrset_t *src_opt = req->qsource.packet->opt_rr;
+	knot_rrset_t *answ_opt = answer->opt_rr;
+
+	const bool ka_want =
+		req->qsource.flags.tcp &&
+		src_opt != NULL &&
+		knot_edns_get_option(src_opt, KNOT_EDNS_OPTION_TCP_KEEPALIVE) &&
+		answ_opt != NULL;
+	if (!ka_want) {
+		return ctx->state;
+	}
+	const struct worker_ctx *worker = (const struct worker_ctx *)req->daemon_context;
+	assert(worker);
+	const struct network *net = &worker->engine->net;
+	uint64_t timeout = net->tcp.in_idle_timeout / 100;
+	if (timeout > UINT16_MAX) {
+		timeout = UINT16_MAX;
+	}
+	knot_mm_t *pool = &answer->mm;
+	uint16_t ka_size = knot_edns_keepalive_size(timeout);
+	uint8_t ka_buf[ka_size];
+	int ret = knot_edns_keepalive_write(ka_buf, ka_size, timeout);
+	if (ret == KNOT_EOK) {
+		ret = knot_edns_add_option(answ_opt, KNOT_EDNS_OPTION_TCP_KEEPALIVE,
+					   ka_size, ka_buf, pool);
+	}
+	if (ret != KNOT_EOK) {
+		ctx->state = KR_STATE_FAIL;
+	}
+	return ctx->state;
+}
+
+KR_EXPORT
+const kr_layer_api_t *edns_keepalive_layer(struct kr_module *module)
+{
+	static kr_layer_api_t _layer = {
+		.answer_finalize = &edns_keepalive_finalize,
+	};
+	/* Store module reference */
+	_layer.data = module;
+	return &_layer;
+}
+
+KR_MODULE_EXPORT(edns_keepalive);
+
diff --git a/modules/edns_keepalive/edns_keepalive.mk b/modules/edns_keepalive/edns_keepalive.mk
new file mode 100644
index 000000000..4ce2bd95d
--- /dev/null
+++ b/modules/edns_keepalive/edns_keepalive.mk
@@ -0,0 +1,5 @@
+edns_keepalive_CFLAGS := -fPIC
+edns_keepalive_LDFLAGS := -Wl,-undefined -Wl,dynamic_lookup
+edns_keepalive_SOURCES := modules/edns_keepalive/edns_keepalive.c
+$(call make_c_module,edns_keepalive)
+
diff --git a/modules/modules.mk b/modules/modules.mk
index 78b83da36..328c8564f 100644
--- a/modules/modules.mk
+++ b/modules/modules.mk
@@ -31,7 +31,8 @@ modules_TARGETS += bogus_log \
                    serve_stale \
                    detect_time_skew \
                    detect_time_jump \
-                   prefill
+                   prefill \
+                   edns_keepalive
 endif
 
 # Make C module