From d8df29e37d99b7b94b15a306dcb2b7488c9a92ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Thu, 24 Nov 2022 15:03:23 +0100
Subject: [PATCH 1/2] Be more resilient when destroying the httpd requests

Don't restart reading in the send callback after the httpdmgr has been
shut down, and call httpd_request(..., ISC_R_SHUTDOWN, ...) when
shutting down the httpdmgr to reduce code duplication.
---
 lib/isc/httpd.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/lib/isc/httpd.c b/lib/isc/httpd.c
index c91847088d..039de4da1a 100644
--- a/lib/isc/httpd.c
+++ b/lib/isc/httpd.c
@@ -899,14 +899,16 @@ httpd_request(isc_nmhandle_t *handle, isc_result_t eresult,
 	REQUIRE(VALID_HTTPD(httpd));
 
 	REQUIRE(httpd->handle == handle);
-	REQUIRE(httpd->readhandle == handle);
-
-	isc_nm_read_stop(httpd->readhandle);
 
 	if (eresult != ISC_R_SUCCESS) {
 		goto close_readhandle;
 	}
 
+	REQUIRE(httpd->readhandle == handle);
+	REQUIRE((mgr->flags & ISC_HTTPDMGR_SHUTTINGDOWN) == 0);
+
+	isc_nm_read_stop(httpd->readhandle);
+
 	/*
 	 * If we are being called from httpd_senddone(), the last HTTP request
 	 * was processed successfully, reset the last_len to 0, even if there's
@@ -955,6 +957,7 @@ httpd_request(isc_nmhandle_t *handle, isc_result_t eresult,
 	return;
 
 close_readhandle:
+	isc_nm_read_stop(httpd->readhandle);
 	isc_nmhandle_close(httpd->readhandle);
 	isc_nmhandle_detach(&httpd->readhandle);
 }
@@ -977,8 +980,10 @@ isc_httpdmgr_shutdown(isc_httpdmgr_t **httpdmgrp) {
 
 	httpd = ISC_LIST_HEAD(httpdmgr->running);
 	while (httpd != NULL) {
-		isc_nm_read_stop(httpd->readhandle);
-		isc_nmhandle_detach(&httpd->readhandle);
+		if (httpd->readhandle != NULL) {
+			httpd_request(httpd->readhandle, ISC_R_SHUTTINGDOWN,
+				      NULL, httpdmgr);
+		}
 		httpd = ISC_LIST_NEXT(httpd, link);
 	}
 	UNLOCK(&httpdmgr->lock);
@@ -1038,6 +1043,10 @@ httpd_senddone(isc_nmhandle_t *handle, isc_result_t eresult, void *arg) {
 
 	REQUIRE(VALID_HTTPD(httpd));
 
+	if ((httpd->mgr->flags & ISC_HTTPDMGR_SHUTTINGDOWN) != 0) {
+		goto detach;
+	}
+
 	if (eresult == ISC_R_SUCCESS && (httpd->flags & HTTPD_CLOSE) == 0) {
 		/*
 		 * Calling httpd_request() with region NULL restarts
@@ -1049,8 +1058,8 @@ httpd_senddone(isc_nmhandle_t *handle, isc_result_t eresult, void *arg) {
 		isc_nmhandle_close(handle);
 	}
 
+detach:
 	isc_nmhandle_detach(&handle);
-
 	isc__httpd_sendreq_free(req);
 }
 

From 32e0df2a13ebf3eaf3c76a3df663187011e3d793 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Wed, 23 Nov 2022 14:23:40 +0100
Subject: [PATCH 2/2] Add CHANGES and release note for [GL #3693]

---
 CHANGES                     | 5 +++++
 doc/notes/notes-current.rst | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/CHANGES b/CHANGES
index 80f83cb891..cf143a47ea 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,8 @@
+6027.	[bug]		Fix assertion failure in isc_http API used by
+			statschannel if the read callback would be called
+			on HTTP request that has been already closed.
+			[GL #3693]
+
 6026.	[cleanup]	Deduplicate time unit conversion factors.
 			[GL !7033]
 
diff --git a/doc/notes/notes-current.rst b/doc/notes/notes-current.rst
index 12eca88597..0397ae0329 100644
--- a/doc/notes/notes-current.rst
+++ b/doc/notes/notes-current.rst
@@ -52,9 +52,13 @@ Bug Fixes
   10 to 100 to accomodate for some browsers that send more that 10
   headers by default. :gl:`#3670`
 
+
 - Copy TLS identifier when setting up primaries for catalog member
   zones. :gl:`#3638`
 
+- Fix an assertion failure in the statschannel caused by reading from the HTTP
+  connection closed prematurely (connection error, shutdown). :gl:`#3693`
+
 Known Issues
 ~~~~~~~~~~~~