Don't increment network error stats on UV_EOF

When networking statistics was added to the netmgr (in commit
5234a8e00a), two lines were added that
increment the 'STATID_RECVFAIL' statistic: One if 'uv_read_start'
fails and one at the end of the 'read_cb'.  The latter happens
if 'nread < 0'.

According to the libuv documentation, I/O read callbacks (such as for
files and sockets) are passed a parameter 'nread'. If 'nread' is less
than 0, there was an error and 'UV_EOF' is the end of file error, which
you may want to handle differently.

In other words, we should not treat EOF as a RECVFAIL error.

CHANGES

@@ -1,3 +1,6 @@
+5517.	[bug]		Handle 'UV_EOF' differently and don't contribute it to
+			the RECVFAIL statistic count. [GL #2208]
+
 5516.	[func]		The default EDNS buffer size has been changed from 4096
 			to 1232, the EDNS buffer size probing has been removed
 			and ``named`` now sets the DON'T FRAGMENT flag on

bin/tests/system/statistics/tests.sh

@@ -161,6 +161,8 @@ if $FEATURETEST --have-libxml2 && [ -x "${CURL}" ] && [ -x "${XSLTPROC}" ]  ; th
     ${CURL} http://10.53.0.3:${EXTRAPORT1}/xml/v3 > curl.out.${n}.xml 2>/dev/null || ret=1
     ${CURL} http://10.53.0.3:${EXTRAPORT1}/bind9.xsl > curl.out.${n}.xsl 2>/dev/null || ret=1
     ${XSLTPROC} curl.out.${n}.xsl - < curl.out.${n}.xml > xsltproc.out.${n} 2>/dev/null || ret=1
+    cp curl.out.${n}.xml stats.xml.out || ret=1
+
     #
     # grep for expected sections.
     #
@@ -205,6 +207,30 @@ if [ $ret != 0 ]; then echo_i "failed"; fi
 status=`expr $status + $ret`
 n=`expr $n + 1`
 
+ret=0
+echo_i "checking bind9.xml socket statistics ($n)"
+if $FEATURETEST --have-libxml2 && [ -x "${CURL}" ] && [ -x "${XSLTPROC}" ]  ; then
+    # Socket statistics (expect no errors)
+    grep "<counter name=\"TCP4AcceptFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP4BindFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP4ConnFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP4OpenFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP4RecvErr\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP4SendErr\">0</counter>" stats.xml.out >/dev/null || ret=1
+
+    grep "<counter name=\"TCP6AcceptFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP6BindFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP6ConnFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP6OpenFail\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP6RecvErr\">0</counter>" stats.xml.out >/dev/null || ret=1
+    grep "<counter name=\"TCP6SendErr\">0</counter>" stats.xml.out >/dev/null || ret=1
+else
+    echo_i "skipping test as libxml2 and/or curl and/or xsltproc was not found"
+fi
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=`expr $status + $ret`
+n=`expr $n + 1`
+
 ret=0
 echo_i "checking priming queries are counted ($n)"
 grep "1 priming queries" ns3/named.stats

doc/notes/notes-current.rst

@@ -69,3 +69,6 @@ Bug Fixes
 - `named` would start continous rollovers for policies that algorithms
   Ed25519 or Ed448 due to a mismatch in created key size and expected key size.
   [GL #2171]
+
+- Handle `UV_EOF` differently such that it is not treated as a `TCP4RecvErr` or
+  `TCP6RecvErr`. [GL #2208]

lib/isc/netmgr/tcp.c

@@ -803,8 +803,10 @@ read_cb(uv_stream_t *stream, ssize_t nread, const uv_buf_t *buf) {
 	 * This might happen if the inner socket is closing.  It means that
 	 * it's detached, so the socket will be closed.
 	 */
-	if (cb != NULL) {
+	if (nread != UV_EOF) {
 		isc__nm_incstats(sock->mgr, sock->statsindex[STATID_RECVFAIL]);
+	}
+	if (cb != NULL) {
 		isc__nmsocket_clearcb(sock);
 		cb(sock->statichandle, ISC_R_EOF, NULL, cbarg);
 	}