Improve lib detection and .gitignore

.gitignore

@@ -7,3 +7,26 @@ config.log
 config.status
 dist
 autom4te.cache
+Makefile.in
+aclocal.m4
+base/.deps/
+base/.dirstamp
+base/Makefile.in
+common/Makefile.in
+common/lib/.deps/
+common/lib/.dirstamp
+common/lib/Makefile.in
+compile
+config.h
+config.h.in
+configure
+depcomp
+install-sh
+missing
+null/.deps/
+null/.dirstamp
+null/Makefile.in
+ssl/.deps/
+ssl/.dirstamp
+ssl/Makefile.in
+stamp-h1

configure.ac

@@ -13,15 +13,59 @@ AM_PROG_CC_C_O
 AC_PROG_MAKE_SET
 AC_PROG_INSTALL
 
-AC_CHECK_LIB([pcap],[pcap_create])
-AC_CHECK_LIB([ssl], [SSL_library_init])
 
 # Checks for header files.
 AC_FUNC_ALLOCA
-AC_CHECK_HEADERS([arpa/inet.h malloc.h memory.h netdb.h netinet/in.h stdlib.h string.h sys/param.h sys/socket.h sys/time.h unistd.h pcap.h pcap-bpf.h],,[AC_MSG_ERROR([Missing header.])])
+AC_CHECK_HEADERS([arpa/inet.h malloc.h memory.h netdb.h netinet/in.h stdlib.h string.h sys/param.h sys/socket.h sys/time.h unistd.h],,[AC_MSG_ERROR([Missing header.])])
 AC_HEADER_STDC
 AC_HEADER_TIME
 
+have_pcap=no
+AC_SEARCH_LIBS([pcap_create], [pcap], [have_pcap=yes])
+
+if test "x${have_pcap}" = xyes; then
+	AC_CHECK_HEADERS([pcap.h pcap-bpf.h], [], [have_pcap=no])
+fi
+
+if test "x${have_pcap}" = xno; then
+	AC_MSG_ERROR([
+---------------------------------------
+Unable to find libpcap on this system
+Check 'config.log' for more information
+
+On Debian and Ubuntu systems you can
+install the required library and header
+files with
+  apt install libpcap-dev
+---------------------------------------
+	])
+fi
+
+AC_CHECK_LIB([pcap],[pcap_create])
+
+have_ssl=no
+AC_SEARCH_LIBS([OPENSSL_init_ssl], [ssl], [have_ssl=yes])
+
+if test "x${have_ssl}" = xyes; then
+	AC_CHECK_HEADERS([openssl/ssl.h], [], [have_ssl=no])
+fi
+
+if test "x${have_ssl}" = xno; then
+	AC_MSG_ERROR([
+---------------------------------------
+Unable to find libssl on this system
+Check 'config.log' for more information
+
+On Debian and Ubuntu systems you can
+install the required library and header
+files with
+  apt install libssl-dev
+---------------------------------------
+	])
+fi
+
+AC_CHECK_LIB([ssl], [OPENSSL_init_ssl])
+
 # Checks for typedefs, structures, and compiler characteristics.
 AC_CHECK_SIZEOF([unsigned short])
 AC_CHECK_SIZEOF([unsigned int])