From a67b3255426160c55faa9d1d3aa6e7579439b2b4 Mon Sep 17 00:00:00 2001
From: Artem Boldariev <artem@isc.org>
Date: Wed, 4 Sep 2024 18:53:35 +0300
Subject: [PATCH] Implement TCP manual read timer control functionality

This commit adds a manual TCP read timer control mode which is
supposed to override automatic resetting of the timer when any data is
received. That can be accomplished by
`isc__nmhandle_set_manual_timer()`.

This functionality is supposed to be used by multilevel networking
transports which require finer grained control over the read
timer (TLS Stream, DoH).

The commit is essentially an implementation of the functionality from
newer versions of BIND.
---
 lib/isc/netmgr/netmgr-int.h | 11 +++++++++++
 lib/isc/netmgr/netmgr.c     | 19 +++++++++++++++++++
 lib/isc/netmgr/tcp.c        | 26 ++++++++++++++++++++++----
 3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/lib/isc/netmgr/netmgr-int.h b/lib/isc/netmgr/netmgr-int.h
index a99153a8f2..48f2ef99f0 100644
--- a/lib/isc/netmgr/netmgr-int.h
+++ b/lib/isc/netmgr/netmgr-int.h
@@ -1229,6 +1229,7 @@ struct isc_nmsocket {
 
 	isc_barrier_t barrier;
 	bool barrier_initialised;
+	atomic_bool manual_read_timer;
 #ifdef NETMGR_TRACE
 	void *backtrace[TRACE_SIZE];
 	int backtrace_size;
@@ -1547,6 +1548,9 @@ isc__nm_tcp_settimeout(isc_nmhandle_t *handle, uint32_t timeout);
  * Set the read timeout for the TCP socket associated with 'handle'.
  */
 
+void
+isc__nmhandle_tcp_set_manual_timer(isc_nmhandle_t *handle, const bool manual);
+
 void
 isc__nm_async_tcpconnect(isc__networker_t *worker, isc__netievent_t *ev0);
 void
@@ -2278,3 +2282,10 @@ isc__nmsocket_writetimeout_cb(void *data, isc_result_t eresult);
 
 void
 isc__nmsocket_log_tls_session_reuse(isc_nmsocket_t *sock, isc_tls_t *tls);
+
+void
+isc__nmhandle_set_manual_timer(isc_nmhandle_t *handle, const bool manual);
+/*
+ * Set manual read timer control mode - so that it will not get reset
+ * automatically on read nor get started when read is initiated.
+ */
diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index a7b82ce69b..49982767bc 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -1627,6 +1627,7 @@ isc___nmsocket_init(isc_nmsocket_t *sock, isc_nm_t *mgr, isc_nmsocket_type type,
 	atomic_init(&sock->keepalive, false);
 	atomic_init(&sock->connected, false);
 	atomic_init(&sock->timedout, false);
+	atomic_init(&sock->manual_read_timer, false);
 
 	atomic_init(&sock->active_child_connections, 0);
 
@@ -3932,6 +3933,24 @@ isc__nmsocket_log_tls_session_reuse(isc_nmsocket_t *sock, isc_tls_t *tls) {
 		      client_sabuf, local_sabuf);
 }
 
+void
+isc__nmhandle_set_manual_timer(isc_nmhandle_t *handle, const bool manual) {
+	REQUIRE(VALID_NMHANDLE(handle));
+	REQUIRE(VALID_NMSOCK(handle->sock));
+
+	isc_nmsocket_t *sock = handle->sock;
+
+	switch (sock->type) {
+	case isc_nm_tcpsocket:
+		isc__nmhandle_tcp_set_manual_timer(handle, manual);
+		return;
+	default:
+		break;
+	};
+
+	UNREACHABLE();
+}
+
 #ifdef NETMGR_TRACE
 /*
  * Dump all active sockets in netmgr. We output to stderr
diff --git a/lib/isc/netmgr/tcp.c b/lib/isc/netmgr/tcp.c
index db589aecc7..fbe1394ab9 100644
--- a/lib/isc/netmgr/tcp.c
+++ b/lib/isc/netmgr/tcp.c
@@ -784,7 +784,9 @@ isc__nm_async_tcpstartread(isc__networker_t *worker, isc__netievent_t *ev0) {
 		return;
 	}
 
-	isc__nmsocket_timer_start(sock);
+	if (!atomic_load(&sock->manual_read_timer)) {
+		isc__nmsocket_timer_start(sock);
+	}
 }
 
 void
@@ -822,7 +824,9 @@ isc__nm_async_tcppauseread(isc__networker_t *worker, isc__netievent_t *ev0) {
 	REQUIRE(sock->tid == isc_nm_tid());
 	UNUSED(worker);
 
-	isc__nmsocket_timer_stop(sock);
+	if (!atomic_load(&sock->manual_read_timer)) {
+		isc__nmsocket_timer_stop(sock);
+	}
 	isc__nm_stop_reading(sock);
 }
 
@@ -931,8 +935,10 @@ isc__nm_tcp_read_cb(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
 			}
 		}
 
-		/* The timer will be updated */
-		isc__nmsocket_timer_restart(sock);
+		if (!atomic_load(&sock->manual_read_timer)) {
+			/* The timer will be updated */
+			isc__nmsocket_timer_restart(sock);
+		}
 	}
 
 free:
@@ -1521,3 +1527,15 @@ isc__nm_tcp_listener_nactive(isc_nmsocket_t *listener) {
 	INSIST(nactive >= 0);
 	return nactive;
 }
+
+void
+isc__nmhandle_tcp_set_manual_timer(isc_nmhandle_t *handle, const bool manual) {
+	isc_nmsocket_t *sock;
+
+	REQUIRE(VALID_NMHANDLE(handle));
+	sock = handle->sock;
+	REQUIRE(VALID_NMSOCK(sock));
+	REQUIRE(sock->type == isc_nm_tcpsocket);
+
+	atomic_store(&sock->manual_read_timer, manual);
+}