build: use net-snmp-config to configure NetSNMP

The correct method to link to NetSNMP is to use net-snmp-config (which
is like pkg-config). Explicit link to libcrypto is also dropped
(NetSNMP libs are linked to libcrypto, no need to link Quagga to
it). Moreover, @SNMP_INCLUDES@ is dropped because useless. Due to a
bug in configure.ac, it was properly populated.

babeld/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

bgpd/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

configure.ac

@@ -221,8 +221,6 @@ AC_ARG_ENABLE(netlink,
 [  --enable-netlink        force to use Linux netlink interface])
 AC_ARG_ENABLE(broken-aliases,
 [  --enable-broken-aliases enable aliases as distinct interfaces for Linux 2.2.X])
-AC_ARG_WITH(crypto,
-[  --without-crypto        do not use libcrypto in SNMP])
 AC_ARG_ENABLE(snmp,
 [  --enable-snmp           enable SNMP support])
 AC_ARG_WITH(libpam,
@@ -1366,19 +1364,24 @@ dnl ------------------
 dnl check Net-SNMP library
 dnl ------------------
 if test "${enable_snmp}" = "yes"; then
-    if test "$with_crypto" != "no"; then
-        LIBS="${LIBS} -lcrypto";
-    fi
-    AC_CHECK_LIB(netsnmp, asn_parse_int,
-    	[AC_DEFINE(HAVE_SNMP,,SNMP)
-    	 LIBS="${LIBS} -lnetsnmp"],
-    	[AC_MSG_ERROR([--enable-snmp given, but cannot find support for SNMP])])
-
-    AC_CHECK_HEADER([net-snmp/net-snmp-config.h],
-        [],
-        [AC_MSG_ERROR([--enable-snmp given, but cannot find net-snmp-config.h])],
-	QUAGGA_INCLUDES)
-    AC_SUBST(SNMP_INCLUDES)
+   AC_PATH_TOOL([NETSNMP_CONFIG], [net-snmp-config], [no])
+   if test x"$NETSNMP_CONFIG" = x"no"; then
+      AC_MSG_ERROR([--enable-snmp given but unable to find net-snmp-config])
+   fi
+   LIBS="$LIBS `${NETSNMP_CONFIG} --agent-libs`"
+   CFLAGS="`${NETSNMP_CONFIG} --base-cflags` $CFLAGS"
+   AC_MSG_CHECKING([whether we can link to Net-SNMP])
+   AC_LINK_IFELSE([AC_LANG_PROGRAM([
+int main(void);
+],
+[
+{
+  return 0;
+}
+])],[AC_MSG_RESULT(yes)],[
+     AC_MSG_RESULT(no)
+     AC_MSG_ERROR([--enable-snmp given but not usable])])
+   AC_DEFINE(HAVE_SNMP,,SNMP)
 fi
 
 dnl ---------------------------
@@ -1624,7 +1627,7 @@ source code location    : ${srcdir}
 compiler                : ${CC}
 compiler flags          : ${CFLAGS}
 make                    : ${MAKE-make}
-includes                : ${INCLUDES} ${SNMP_INCLUDES}
+includes                : ${INCLUDES}
 linker flags            : ${LDFLAGS} ${LIBS} ${LIBCAP} ${LIBREADLINE} ${LIBM}
 state file directory    : ${quagga_statedir}
 config file directory   : `eval echo \`echo ${sysconfdir}\``

lib/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 
 lib_LTLIBRARIES = libzebra.la

ospf6d/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

ospfd/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ $(LOCAL_OPTS) -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

ripd/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

ripngd/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
 

vtysh/extract.pl.in

@@ -63,7 +63,7 @@ $ignore{'"show history"'} = "ignore";
 foreach (@ARGV) {
     $file = $_;
 
-    open (FH, "cpp -DHAVE_CONFIG_H -DVTYSH_EXTRACT_PL -DHAVE_IPV6 -I@top_builddir@ -I@srcdir@/ -I@srcdir@/.. -I@top_srcdir@/lib -I@top_builddir@/lib -I@top_srcdir@/isisd/topology @SNMP_INCLUDES@ @CPPFLAGS@ $file |");
+    open (FH, "cpp -DHAVE_CONFIG_H -DVTYSH_EXTRACT_PL -DHAVE_IPV6 -I@top_builddir@ -I@srcdir@/ -I@srcdir@/.. -I@top_srcdir@/lib -I@top_builddir@/lib -I@top_srcdir@/isisd/topology @CPPFLAGS@ $file |");
     local $/; undef $/;
     $line = <FH>;
     close (FH);

zebra/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib @SNMP_INCLUDES@
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\" -DMULTIPATH_NUM=@MULTIPATH_NUM@
 INSTALL_SDATA=@INSTALL@ -m 600