Update Makefile and fix compilation errors

Makefile

@@ -1,11 +1,17 @@
 ifdef DEBUG
-MFLAGS   = DEBUG=${DEBUG}
+CXXFLAGS ?= -g -DDEBUG
 else
-MFLAGS   =
+CXXFLAGS ?= -O3
 endif
 
-MANDIR  = ${DESTDIR}/usr/share/man
-SBINDIR = ${DESTDIR}/usr/sbin
+PREFIX  ?= /usr/local
+CXX     ?= g++
+LDFLAGS ?= -lconfuse
+OBJ     ?= src/log.o src/ndppd.o src/iface.o src/proxy.o src/address.o \
+           src/rule.o src/session.o src/conf.o
+GZIP    ?= /bin/gzip
+MANDIR  ?= ${DESTDIR}${PREFIX}/share/man
+SBINDIR ?= ${DESTDIR}${PREFIX}/sbin
 
 all: ndppd ndppd.1.gz ndppd.conf.5.gz
 
@@ -16,15 +22,17 @@ install: all
 	cp ndppd.1.gz ${MANDIR}/man1
 	cp ndppd.conf.5.gz ${MANDIR}/man5
 
-ndppd:
-	cd src && make ${MFLAGS} all && cp ndppd ..
-
-clean:
-	rm -f ndppd ndppd.conf.5.gz ndppd.1.gz
-	cd src && make clean
-
 ndppd.1.gz:
-	gzip < ndppd.1 > ndppd.1.gz
+	${GZIP} < ndppd.1 > ndppd.1.gz
 
 ndppd.conf.5.gz:
-	gzip < ndppd.conf.5 > ndppd.conf.5.gz
+	${GZIP} < ndppd.conf.5 > ndppd.conf.5.gz
+
+ndppd: ${OBJ}
+	${CXX} -o ndppd ${LDFLAGS} ${OBJ}
+
+.cc.o:
+	${CXX} -c $(CXXFLAGS) -o $@ $<
+
+clean:
+	rm -f ndppd ndppd.conf.5.gz ndppd.1.gz ${OBJ}

src/Makefile

@@ -1,23 +0,0 @@
-ifdef DEBUG
-CFLAGS   = -g -DDEBUG
-else
-CFLAGS   = -O3
-endif
-
-CC       = g++
-LDFLAGS  = -lconfuse
-OBJ      = log.o ndppd.o iface.o proxy.o address.o rule.o session.o conf.o
-
-
-all: ndppd
-
-ndppd: ${OBJ}
-	${CC} -o ndppd ${LDFLAGS} ${OBJ}
-
-.cc.o:
-	${CC} -c $(CFLAGS) $<
-
-clean:
-	rm -f ndppd ${OBJ}
- 
- 

src/iface.cc

@@ -13,9 +13,10 @@
 //
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <cstddef>
 
 #include <unistd.h>