testbench: add test for known message-garbling case

see also https://github.com/rsyslog/rsyslog/issues/1658

tests/Makefile.am

@@ -97,6 +97,7 @@ TESTS +=  \
 	no-parser-errmsg.sh \
 	da-mainmsg-q.sh \
 	validation-run.sh \
+	msgdup.sh \
 	empty-ruleset.sh \
 	imtcp-discard-truncated-msg.sh \
 	imtcp-basic.sh \
@@ -975,6 +976,7 @@ EXTRA_DIST= \
 	testsuites/da-mainmsg-q.conf \
 	diskqueue-fsync.sh \
 	testsuites/diskqueue-fsync.conf \
+	msgdup.sh \
 	empty-ruleset.sh \
 	testsuites/empty-ruleset.conf \
 	imtcp-discard-truncated-msg.sh \

tests/msgdup.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+# This tests the border case that a message is exactly as large as the default
+# buffer size (101 chars) and is reduced in size afterwards. This has been seen
+# in practice.
+# see also https://github.com/rsyslog/rsyslog/issues/1658
+# Copyright (C) 2017 by Rainer Gerhards, released under ASL 2.0 (2017-07-11)
+if [ `uname` = "SunOS" ] ; then
+   echo "This test currently does not work on all flavors of Solaris."
+   exit 77
+fi
+
+. $srcdir/diag.sh init
+. $srcdir/diag.sh generate-conf
+. $srcdir/diag.sh add-conf '
+module(load="../plugins/imuxsock/.libs/imuxsock" sysSock.use="off")
+input(type="imuxsock" Socket="testbench_socket")
+
+template(name="outfmt" type="string" string="%msg%\n")
+
+ruleset(name="rs" queue.type="LinkedList") {
+	action(type="omfile" file="rsyslog.out.log" template="outfmt")
+	stop
+}
+
+*.notice call rs
+'
+. $srcdir/diag.sh startup
+logger -d -u testbench_socket -t RSYSLOG_TESTBENCH 'test 01234567890123456789012345678901234567890123456789012345
+' #Note: LF at end of message is IMPORTANT, it is bug triggering condition
+# the sleep below is needed to prevent too-early termination of rsyslogd
+./msleep 100
+. $srcdir/diag.sh shutdown-when-empty # shut down rsyslogd when done processing messages
+. $srcdir/diag.sh wait-shutdown	# we need to wait until rsyslogd is finished!
+echo " test 01234567890123456789012345678901234567890123456789012345" | cmp rsyslog.out.log
+if [ ! $? -eq 0 ]; then
+  echo "msgdup.sh failed"
+  echo contents of rsyslog.out.log:
+  echo \"`cat rsyslog.out.log`\"
+  exit 1
+fi;
+. $srcdir/diag.sh exit