From: Artem Boldariev <artem@boldariev.com>
Date: Fri, 2 Jun 2023 11:28:50 +0000 (+0300)
Subject: Use appropriately sized send buffers for DNS messages over TCP
X-Git-Tag: v9.19.14~9^2~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d8a5feb5567aaebcc11c5b20b9b667c040c4d22a;p=thirdparty%2Fbind9.git

Use appropriately sized send buffers for DNS messages over TCP

This commit changes send buffers allocation strategy for stream based
transports. Before that change we would allocate a dynamic buffers
sized at 64Kb even when we do not need that much. That could lead to
high memory usage on server. Now we resize the send buffer to match
the size of the actual data, freeing the memory at the end of the
buffer for being reused later.
---

diff --git a/lib/ns/client.c b/lib/ns/client.c
index 7dc52b43c44..395ebde6bf3 100644
--- a/lib/ns/client.c
+++ b/lib/ns/client.c
@@ -331,6 +331,7 @@ client_allocsendbuf(ns_client_t *client, isc_buffer_t *buffer,
 		INSIST(client->tcpbuf == NULL);
 		client->tcpbuf = isc_mem_get(client->manager->mctx,
 					     NS_CLIENT_TCP_BUFFER_SIZE);
+		client->tcpbuf_size = NS_CLIENT_TCP_BUFFER_SIZE;
 		data = client->tcpbuf;
 		isc_buffer_init(buffer, data, NS_CLIENT_TCP_BUFFER_SIZE);
 	} else {
@@ -363,7 +364,17 @@ client_sendpkg(ns_client_t *client, isc_buffer_t *buffer) {
 
 	REQUIRE(client->sendhandle == NULL);
 
-	isc_buffer_usedregion(buffer, &r);
+	if (isc_buffer_base(buffer) == client->tcpbuf) {
+		size_t used = isc_buffer_usedlength(buffer);
+		client->tcpbuf = isc_mem_reget(client->manager->mctx,
+					       client->tcpbuf,
+					       client->tcpbuf_size, used);
+		client->tcpbuf_size = used;
+		r.base = client->tcpbuf;
+		r.length = used;
+	} else {
+		isc_buffer_usedregion(buffer, &r);
+	}
 	isc_nmhandle_attach(client->handle, &client->sendhandle);
 
 	if (isc_nm_is_http_handle(client->handle)) {
@@ -434,8 +445,7 @@ ns_client_sendraw(ns_client_t *client, dns_message_t *message) {
 done:
 	if (client->tcpbuf != NULL) {
 		isc_mem_put(client->manager->mctx, client->tcpbuf,
-			    NS_CLIENT_TCP_BUFFER_SIZE);
-		client->tcpbuf = NULL;
+			    client->tcpbuf_size);
 	}
 
 	ns_client_drop(client, result);
@@ -719,8 +729,7 @@ renderend:
 cleanup:
 	if (client->tcpbuf != NULL) {
 		isc_mem_put(client->manager->mctx, client->tcpbuf,
-			    NS_CLIENT_TCP_BUFFER_SIZE);
-		client->tcpbuf = NULL;
+			    client->tcpbuf_size);
 	}
 
 	if (cleanup_cctx) {
@@ -1609,7 +1618,7 @@ ns__client_reset_cb(void *client0) {
 	ns_client_endrequest(client);
 	if (client->tcpbuf != NULL) {
 		isc_mem_put(client->manager->mctx, client->tcpbuf,
-			    NS_CLIENT_TCP_BUFFER_SIZE);
+			    client->tcpbuf_size);
 	}
 
 	if (client->keytag != NULL) {
diff --git a/lib/ns/include/ns/client.h b/lib/ns/include/ns/client.h
index 28f4bfd9292..04dbb9c4a8b 100644
--- a/lib/ns/include/ns/client.h
+++ b/lib/ns/include/ns/client.h
@@ -171,6 +171,7 @@ struct ns_client {
 					 (query, update, notify) */
 	isc_nmhandle_t *updatehandle; /* Waiting for update callback */
 	unsigned char  *tcpbuf;
+	size_t		tcpbuf_size;
 	dns_message_t  *message;
 	unsigned char  *sendbuf;
 	dns_rdataset_t *opt;