[PATCH v2] ipvsadm: detect LIBS and CFLAGS for libnl versions

[Jesper Dangaard Brouer <jbrouer@redhat.com>]

Automated detecting of LIBS and CFLAGS for different versions
of libnl via using pkg-config, in the Makefiles.  This should
make it easier to compile on different distributions.

Detecting in prioritized order from the most recent version, and only
the first detected lib is used. Thus, supporting several libnl version
being installed on the same system.

Only tested with libnl-1 and libnl-3.0, but also adding support for
libnl-2.0.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
V2: Fix small bug noticed by Daniel, fall-through libs case missed a "l"

 Makefile         |    8 +++++++-
 libipvs/Makefile |    7 +++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 6e36d79..91a2991 100644
--- a/Makefile
+++ b/Makefile
@@ -65,7 +65,13 @@ RPMBUILD = $(shell				\
 OBJS		= ipvsadm.o config_stream.o dynamic_array.o
 LIBS		= -lpopt
 ifneq (0,$(HAVE_NL))
-LIBS		+= -lnl
+LIBS		+= $(shell \
+		if which pkg-config > /dev/null 2>&1; then \
+		  if   pkg-config --libs libnl-genl-3.0  2> /dev/null; then :;\
+		  elif pkg-config --libs libnl-2.0       2> /dev/null; then :;\
+		  elif pkg-config --libs libnl-1         2> /dev/null; then :;\
+		  fi; \
+		else echo "-lnl"; fi)
 endif
 DEFINES		= -DVERSION=\"$(VERSION)\" -DSCHEDULERS=\"$(SCHEDULERS)\" \
 		  -DPE_LIST=\"$(PE_LIST)\" $(POPT_DEFINE)
diff --git a/libipvs/Makefile b/libipvs/Makefile
index eafc3e5..f845c8b 100644
--- a/libipvs/Makefile
+++ b/libipvs/Makefile
@@ -4,6 +4,13 @@ CC		= gcc
 CFLAGS		= -Wall -Wunused -Wstrict-prototypes -g -fPIC
 ifneq (0,$(HAVE_NL))
 CFLAGS		+= -DLIBIPVS_USE_NL
+CFLAGS		+= $(shell \
+		if which pkg-config > /dev/null 2>&1; then \
+		  if   pkg-config --cflags libnl-3.0  2> /dev/null; then :; \
+		  elif pkg-config --cflags libnl-2.0  2> /dev/null; then :; \
+		  elif pkg-config --cflags libnl-1    2> /dev/null; then :; \
+		  fi; \
+		fi)
 endif
 
 INCLUDE		+= $(shell if [ -f ../../ip_vs.h ]; then	\