user01010111 · Sep 15, 2026 · Sep 15, 2026 · Sep 15, 2026 · Sep 18, 2026 · Sep 20, 2026
diff --git a/Makefile.am b/Makefile.am
@@ -571,9 +571,9 @@ all/tests/NIT: all/clients all/server all-drivers all-recursive/tools all-recurs
 ### LIB-Requires-ext: #COMMENTED-AWAY# common/libcommon.la
 ### Requires-ext: common/libcommon.la common/libnutconf.la
 ### Requires-ext: clients/libnutclient.la clients/libnutclientstub.la
-### Requires-ext: drivers/libdummy_mockdrv.la
+### Requires-ext: drivers/libdummy_mockdrv.la tools/nut-scanner/libnutscan.la
 ### Requires-int: libdriverstubusb.la
-all/tests: all-libs-local/tests all-libs-local/drivers all-libs-local/common all-libs-local/clients @dotMAKE@
+all/tests: all-libs-local/tests all-libs-local/drivers all-libs-local/common all-libs-local/clients all-libs-local/tools/nut-scanner @dotMAKE@
 	+@NUT_VERSION_H_GENERATED=true; export NUT_VERSION_H_GENERATED; \
 	  $(SUBDIR_TGT_RULE)
 

diff --git a/NEWS.adoc b/NEWS.adoc
@@ -55,6 +55,18 @@ https://github.com/networkupstools/nut/milestone/13
       extracting the response. Returned keys and descriptions remain byte
       sequences. [issue #3621]
     * `nut-scanner` tool updates:
+      - Retry SNMP hosts whose session could not open because the process
+        ran out of file descriptors. After the original SNMP scans finish,
+        retry those hosts one at a time and report any remaining descriptor
+        exhaustion. Other scan types and their limits are unchanged.
+        [issue #2576]
+      - Keep serial scan permits balanced when admission or thread creation
+        fails, and retain port names until all started workers finish if
+        allocating thread tracking fails.
+      - Balance concurrency permits and worker ownership during SNMP, IPMI,
+        NUT and XML/HTTP scans, including disabled protocol limits and failed
+        thread creation. Keep NUT authentication data alive until the scan
+        worker has finished. [issue #1166]
       - Mutexes used in parallelized scans were not properly released on
         failure code paths (impacts likely all 2.8.x until now). [PR #3551]
       - Third-party libraries which `nut-scanner` loads dynamically (libusb,

diff --git a/configure.ac b/configure.ac
@@ -6444,6 +6444,7 @@ AC_SUBST(LIBGIO_CFLAGS)
 AC_SUBST(LIBGIO_LIBS)
 AC_SUBST(LIBNETSNMP_CFLAGS)
 AC_SUBST(LIBNETSNMP_LIBS)
+AC_SUBST(LIBNETSNMP_LIBS_EXEC)
 AC_SUBST(LIBREGEX_LIBS)
 AC_SUBST(LIBUSB_CFLAGS)
 AC_SUBST(LIBUSB_LIBS)

diff --git a/m4/nut_check_libnetsnmp.m4 b/m4/nut_check_libnetsnmp.m4
@@ -1,6 +1,6 @@
 dnl Check for LIBNETSNMP compiler flags. On success, set
 dnl nut_have_libnetsnmp="yes" and set LIBNETSNMP_CFLAGS and
-dnl LIBNETSNMP_LIBS. On failure, set nut_have_libnetsnmp="no".
+dnl LIBNETSNMP_LIBS and LIBNETSNMP_LIBS_EXEC. On failure, set nut_have_libnetsnmp="no".
 dnl This macro can be run multiple times, but will do the
 dnl checking only once.
 
@@ -18,6 +18,9 @@ AC_DEFUN([NUT_CHECK_LIBNETSNMP],
         NUT_ARG_WITH_LIBOPTS_LIBS([snmp], [auto], [Net-SNMP])
 
         nut_noncv_checked_libnetsnmp_now=no
+        dnl Refresh older caches which did not retain executable linker flags.
+        AS_IF([test "${nut_cv_LIBNETSNMP_LIBS_EXEC+set}" != set],
+            [AS_UNSET([nut_cv_checked_libnetsnmp])])
         AC_CACHE_VAL([nut_cv_checked_libnetsnmp], [
             nut_noncv_checked_libnetsnmp_now=yes
 
@@ -129,6 +132,8 @@ AC_DEFUN([NUT_CHECK_LIBNETSNMP],
             )
             AC_MSG_RESULT([${depLIBS} (source: ${depLIBS_SOURCE})])
 
+            depLIBS_EXEC="${depLIBS}"
+
             dnl Check if the Net-SNMP library is usable
             CFLAGS="${CFLAGS_ORIG} ${depCFLAGS}"
             LIBS="${LIBS_ORIG} ${depLIBS}"
@@ -150,6 +155,8 @@ AC_DEFUN([NUT_CHECK_LIBNETSNMP],
                         [*mingw*], [
                             AC_MSG_NOTICE([mingw builds of net-snmp might provide only a static library - retrying for that])
                             depLIBS="`$PKG_CONFIG --silence-errors --libs --static netsnmp 2>/dev/null`"
+                            dnl Executables need ordinary flags after their static libraries.
+                            depLIBS_EXEC="${depLIBS}"
                             dnl # Some workarouds here, to avoid libtool bailing out like this:
                             dnl # *** Warning: This system cannot link to static lib archive /usr/x86_64-w64-mingw32/lib//libnetsnmp.la.
                             dnl # *** I have the capability to make that library automatically link in when
@@ -174,12 +181,14 @@ AC_DEFUN([NUT_CHECK_LIBNETSNMP],
 
             nut_cv_LIBNETSNMP_CFLAGS=""
             nut_cv_LIBNETSNMP_LIBS=""
+            nut_cv_LIBNETSNMP_LIBS_EXEC=""
             nut_cv_SOFILE_LIBNETSNMP=""
             nut_cv_SONAME_LIBNETSNMP=""
             nut_cv_SOPATH_LIBNETSNMP=""
             AS_IF([test "${nut_cv_have_libnetsnmp}" = "yes"], [
                 nut_cv_LIBNETSNMP_CFLAGS="${depCFLAGS}"
                 nut_cv_LIBNETSNMP_LIBS="${depLIBS}"
+                nut_cv_LIBNETSNMP_LIBS_EXEC="${depLIBS_EXEC}"
 
                 AC_CACHE_CHECK([for defined usmAESPrivProtocol],
                     [nut_cv_NUT_HAVE_LIBNETSNMP_usmAESPrivProtocol],
@@ -378,13 +387,15 @@ int num = NETSNMP_DRAFT_BLUMENTHAL_AES_04 + 1; /* if defined, NETSNMP_DRAFT_BLUM
             AC_CACHE_VAL([nut_cv_prefer_NET_SNMP_CONFIG], [])
             AC_CACHE_VAL([nut_cv_LIBNETSNMP_CFLAGS], [])
             AC_CACHE_VAL([nut_cv_LIBNETSNMP_LIBS], [])
+            AC_CACHE_VAL([nut_cv_LIBNETSNMP_LIBS_EXEC], [])
             AC_CACHE_VAL([nut_cv_LIBNETSNMP_CFLAGS_SOURCE], [])
             AC_CACHE_VAL([nut_cv_LIBNETSNMP_LIBS_SOURCE], [])
             AC_CACHE_VAL([nut_cv_SOFILE_LIBNETSNMP], [])
             AC_CACHE_VAL([nut_cv_SOPATH_LIBNETSNMP], [])
 
             unset depCFLAGS
             unset depLIBS
+            unset depLIBS_EXEC
             unset depCFLAGS_SOURCE
             unset depLIBS_SOURCE
 
@@ -431,6 +442,7 @@ int num = NETSNMP_DRAFT_BLUMENTHAL_AES_04 + 1; /* if defined, NETSNMP_DRAFT_BLUM
 
             LIBNETSNMP_CFLAGS="${nut_cv_LIBNETSNMP_CFLAGS}"
             LIBNETSNMP_LIBS="${nut_cv_LIBNETSNMP_LIBS}"
+            LIBNETSNMP_LIBS_EXEC="${nut_cv_LIBNETSNMP_LIBS_EXEC}"
 
             dnl For nut-scanner style autoloading:
             SOPATH_LIBNETSNMP="${nut_cv_SOPATH_LIBNETSNMP}"

diff --git a/tests/Makefile.am b/tests/Makefile.am
@@ -56,7 +56,9 @@ $(top_builddir)/common/libcommon.la \
 $(top_builddir)/common/libparseconf.la \
 $(top_builddir)/clients/libupsclient.la \
 $(top_builddir)/clients/libnutclient.la \
-$(top_builddir)/clients/libnutclientstub.la: dummy @dotMAKE@
+$(top_builddir)/clients/libnutclientstub.la \
+$(top_builddir)/tools/nut-scanner/nutscan-snmp.h \
+$(top_builddir)/tools/nut-scanner/libnutscan.la: dummy @dotMAKE@
 	+@cd $(@D) && $(MAKE) $(AM_MAKEFLAGS) $(@F)
 
 $(top_builddir)/clients/upslog$(EXEEXT): dummy @dotMAKE@
@@ -66,6 +68,9 @@ $(top_builddir)/clients/upslog$(EXEEXT): dummy @dotMAKE@
 # started from scratch right in this dir get dependencies in proper order
 # (sub-makes are independent as far as trying to write into same files):
 $(top_builddir)/common/libcommon.la $(top_builddir)/common/libcommonclient.la: $(top_builddir)/common/libparseconf.la
+# These independent sub-makes share the replacement-function objects.
+# Finish one library before the other can rebuild those objects.
+$(top_builddir)/common/libcommon.la: $(top_builddir)/common/libcommonclient.la
 $(top_builddir)/common/libcommonversion.la: $(top_builddir)/include/nut_version.h
 $(top_builddir)/clients/libnutclientstub.la: $(top_builddir)/clients/libnutclient.la
 
@@ -104,6 +109,13 @@ NUT_LIBCOMMON = $(top_builddir)/common/libcommon.la
 
 endif !ENABLE_SHARED_PRIVATE_LIBS
 
+# Finish shared dependencies before the scanner's independent sub-make
+# (normally invoked only if building WITH_NUT_SCANNER).
+$(top_builddir)/tools/nut-scanner/libnutscan.la: $(NUT_LIBCOMMON) $(top_builddir)/common/libcommonversion.la $(top_builddir)/clients/libupsclient.la
+# The scanner library generates this header before the tests can include it
+# (if building WITH_NUT_SCANNER and WITH_SNMP).
+$(top_builddir)/tools/nut-scanner/nutscan-snmp.h: $(top_builddir)/tools/nut-scanner/libnutscan.la
+
 TESTS += test_cgilib
 test_cgilib_SOURCES = test_cgilib.c
 nodist_test_cgilib_SOURCES = cgilib.c
@@ -312,6 +324,68 @@ endif !WITH_OPENSSL
 endif WITH_SSL
 endif WITH_SNMP
 
+# Compile each scanner's actual admission loop with offline worker probes.
+if WITH_NUT_SCANNER
+NUTSCAN_TEST_CFLAGS = $(AM_CFLAGS) -I$(top_srcdir)/tools/nut-scanner -I$(top_builddir)/tools/nut-scanner -I$(top_srcdir)/clients $(LIBIPMI_CFLAGS)
+NUTSCAN_TEST_LDADD = $(NUT_LIBCOMMON) $(top_builddir)/tools/nut-scanner/libnutscan.la $(LIBLTDL_LIBS) $(SEMLIBS) $(NETLIBS)
+if WITH_SSL
+NUTSCAN_TEST_CFLAGS += $(LIBSSL_CFLAGS)
+NUTSCAN_TEST_LDADD += $(LIBSSL_LIBS)
+endif WITH_SSL
+# Any fixture may pull the SNMP scanner from static libnutscan.
+if WITH_SNMP_STATIC
+NUTSCAN_TEST_LDADD += $(LIBNETSNMP_LIBS_EXEC)
+endif WITH_SNMP_STATIC
+
+if WITH_SNMP
+nutscan-thread-test.c nutscan-snmp-retry-test.c: $(top_builddir)/tools/nut-scanner/nutscan-snmp.h
+
+TESTS += nutscan-snmp-retry-test
+nutscan_snmp_retry_test_SOURCES = nutscan-snmp-retry-test.c
+nutscan_snmp_retry_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) $(LIBNETSNMP_CFLAGS)
+nutscan_snmp_retry_test_LDADD = $(NUTSCAN_TEST_LDADD)
+nutscan_snmp_retry_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_snmp.c $(top_builddir)/tools/nut-scanner/nutscan-snmp.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+endif WITH_SNMP
+
+if WITH_THREADING
+TESTS += nutscan-serial-test
+nutscan_serial_test_SOURCES = nutscan-thread-test.c
+nutscan_serial_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) -DNUTSCAN_TEST_PROTOCOL=5
+nutscan_serial_test_LDADD = $(top_builddir)/drivers/libserial-nutscan.la $(NUTSCAN_TEST_LDADD) $(SERLIBS)
+nutscan_serial_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_eaton_serial.c $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+
+TESTS += nutscan-nut-test
+nutscan_nut_test_SOURCES = nutscan-thread-test.c
+nutscan_nut_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) -DNUTSCAN_TEST_PROTOCOL=3
+nutscan_nut_test_LDADD = $(NUTSCAN_TEST_LDADD)
+nutscan_nut_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_nut.c $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+
+if WITH_SNMP
+TESTS += nutscan-snmp-test
+nutscan_snmp_test_SOURCES = nutscan-thread-test.c
+nutscan_snmp_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) $(LIBNETSNMP_CFLAGS) -DNUTSCAN_TEST_PROTOCOL=1
+nutscan_snmp_test_LDADD = $(NUTSCAN_TEST_LDADD)
+nutscan_snmp_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_snmp.c $(top_builddir)/tools/nut-scanner/nutscan-snmp.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+endif WITH_SNMP
+
+if WITH_IPMI
+TESTS += nutscan-ipmi-test
+nutscan_ipmi_test_SOURCES = nutscan-thread-test.c
+nutscan_ipmi_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) -DNUTSCAN_TEST_PROTOCOL=2
+nutscan_ipmi_test_LDADD = $(NUTSCAN_TEST_LDADD)
+nutscan_ipmi_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_ipmi.c $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+endif WITH_IPMI
+
+if WITH_NEON
+TESTS += nutscan-xml-test
+nutscan_xml_test_SOURCES = nutscan-thread-test.c
+nutscan_xml_test_CFLAGS = $(NUTSCAN_TEST_CFLAGS) $(LIBNEON_CFLAGS) -DNUTSCAN_TEST_PROTOCOL=4
+nutscan_xml_test_LDADD = $(NUTSCAN_TEST_LDADD)
+nutscan_xml_test_DEPENDENCIES = $(top_srcdir)/tools/nut-scanner/scan_xml_http.c $(top_srcdir)/tools/nut-scanner/nutscan-thread.h $(top_srcdir)/tools/nut-scanner/nutscan-thread.c $(top_builddir)/tools/nut-scanner/libnutscan.la $(NUT_LIBCOMMON)
+endif WITH_NEON
+endif WITH_THREADING
+endif WITH_NUT_SCANNER
+
 ### Optional tests which can not be built everywhere
 # List of src files for CppUnit tests
 CPPUNITTESTSRC = example.cpp nutclienttest.cpp