dhcpsd: -w waits for dynmically created interfaces (#4)

* dhcpsd: -w waits for dynmically created interfaces

The interface you may want to configure might not
exist when dhcpsd first starts.

The -w option will cause dhcpcd to only configure
an interface when it recieves a message on it.
We assume if we have received a message it's
ready as we cannot guess which address to use.
So ensure the server address is added before the
interface is marked as up!

If the interface is marked as down then the
interface is deconfigured.

This allows dhcpsd to be used in-place of the
macOS DHCP server as provided by the UTM
framework.

Author: rsmarples

configure

@@ -311,19 +311,19 @@ EOF
 	esac
 
 	if [ "$SANITIZEADDRESS" = yes ]; then
-		printf "Testing compiler supports address sanitisation ..."
+		printf "Testing compiler supports address sanitisation ... "
 	cat <<EOF >_test.c
 int main(void) {
 	return 0;
 }
 EOF
-		if $CC -fsanitize=address _test.c -o _test 2>&3; then
+		if $CC -fsanitize=address,undefined _test.c -o _test 2>&3; then
 			echo "yes"
 			echo "SANITIZEADDRESS=	yes" >>$CONFIG_MK
 			echo "CPPFLAGS+=	-DASAN" >>$CONFIG_MK
-			echo "CFLAGS+=	-fsanitize=address" >>$CONFIG_MK
+			echo "CFLAGS+=	-fsanitize=address,undefined" >>$CONFIG_MK
 			echo "CFLAGS+=	-fno-omit-frame-pointer" >>$CONFIG_MK
-			echo "LDFLAGS+=	-fsanitize=address" >>$CONFIG_MK
+			echo "LDFLAGS+=	-fsanitize=address,undefined" >>$CONFIG_MK
 		else
 			echo "no"
 		fi
@@ -591,6 +591,50 @@ fi
 rm -rf _inet_ntoa.* _inet_ntoa
 $abort && exit 1
 
+if [ -z "$LINK_SRC" ]; then
+	printf "Testing for route ... "
+	cat << EOF >_route.c
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <net/route.h>
+int main(void) {
+	struct rt_msghdr rtm = { .rtm_type = RTM_IFINFO };
+	return (int)rtm.rtm_type;
+}
+EOF
+	if $XCC _route.c -o _route 2>&3; then
+		LINK_SRC="route.c"
+		echo "yes"
+	else
+		echo "no"
+	fi
+	rm -rf _route.* _route
+fi
+
+if [ -z "$LINK_SRC" ]; then
+	printf "Testing for netlink ... "
+	cat << EOF >_netlink.c
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <sys/socket.h>
+int main(void) {
+	return 0;
+}
+EOF
+	if $XCC _netlink.c -o _netlink 2>&3; then
+		LINK_SRC="netlink.c"
+		echo "yes"
+	else
+		echo "no"
+	fi
+	rm -rf _netlink.* _netlink
+fi
+if [ -z "$LINK_SRC" ]; then
+	echo "no mechanism for detecting interface departures found" >&2
+	exit 1
+fi
+echo "LINK_SRC=	$LINK_SRC" >>$CONFIG_MK
+
 if [ -z "$SETPROCTITLE" ]; then
 	printf "Testing for setproctitle ... "
 	cat << EOF >_setproctitle.c
@@ -742,7 +786,5 @@ echo "   LIBDIR =		$LIBDIR"
 echo "   DATADIR =		$DATADIR"
 echo "   RUNDIR =		$RUNDIR"
 echo "   MANDIR =		$MANDIR"
-if [ "$PRIVSEP" = yes ]; then
-	echo "   PRIVSEPUSER =	$PRIVSEP_USER"
-fi
+echo "   DHCPSD_USER =	$DHCPSD_USER"
 echo

src/Makefile

@@ -4,15 +4,16 @@ PROG=		dhcpsd
 SRCS=		dhcpsd.c common.c eloop.c if.c logerr.c
 SRCS+=		bpf.c dhcp.c dhcp_lease.c
 SRCS+=		if_none.c if_ether.c
-SRCS+=		service.c unpriv.c
+SRCS+=		service.c priv.c unpriv.c
 SRCS+=		plugin.c
-OBJS+=          ${SRCS:.c=.o}
+SRCS+=		${LINK_SRC}
+OBJS+=      ${SRCS:.c=.o}
 
 PVENDOR_SRCS=	${VENDOR_SRCS:vendor/%=${TOP}/vendor/%}
-OBJS+=		${PVENDOR_SRCS:.c=.o}
+OBJS+=			${PVENDOR_SRCS:.c=.o}
 
 PCOMPAT_SRCS=	${COMPAT_SRCS:compat/%=${TOP}/compat/%}
-OBJS+=		${PCOMPAT_SRCS:.c=.o}
+OBJS+=			${PCOMPAT_SRCS:.c=.o}
 
 CFLAGS?=	-O2
 SUBDIRS=	plugins

src/bpf.c

@@ -397,7 +397,7 @@ bpf_open(const struct interface *ifp, int (*filter)(const struct bpf *),
 #else
 	struct bpf_version pv = { .bv_major = 0, .bv_minor = 0 };
 	struct ifreq ifr = { .ifr_flags = 0 };
-#if 0
+#if 1
 	int ibuf_len = 0;
 #endif
 	unsigned int imm;
@@ -506,7 +506,6 @@ bpf_open(const struct interface *ifp, int (*filter)(const struct bpf *),
 #ifdef __linux__
 	UNUSED(flags);
 #else
-#if 0
 	if (flags & (O_RDONLY | O_RDWR)) {
 		/* Get the required BPF buffer length from the kernel. */
 		if (ioctl(bpf->bpf_fd, BIOCGBLEN, &ibuf_len) == -1)
@@ -517,7 +516,6 @@ bpf_open(const struct interface *ifp, int (*filter)(const struct bpf *),
 		if (bpf->bpf_buffer == NULL)
 			goto eexit;
 	}
-#endif
 #endif
 
 	return bpf;
@@ -568,7 +566,8 @@ bpf_read(struct bpf *bpf, void *data, size_t len)
 			bytes = (ssize_t)len;
 		else
 			bytes = (ssize_t)packet.bh_caplen;
-		memcpy(data, payload, (size_t)bytes);
+		if (data)
+			memcpy(data, payload, (size_t)bytes);
 	next:
 		bpf->bpf_pos += BPF_WORDALIGN(
 		    packet.bh_hdrlen + packet.bh_caplen);

src/common.c

@@ -30,6 +30,10 @@
 
 #include <netinet/in.h>
 
+#ifdef AF_PACKET
+#include <netpacket/packet.h>
+#endif
+
 #include <arpa/inet.h>
 #include <arpa/nameser.h>
 #include <ctype.h>
@@ -414,13 +418,30 @@ inet_ntocidr(struct in_addr *addr)
 	return cidr;
 }
 
-size_t
+int
+sa_is_link(const struct sockaddr *sa)
+{
+#ifdef AF_LINK
+	return sa->sa_family == AF_LINK ? 1 : 0;
+#elif defined(AF_PACKET)
+	return sa->sa_family == AF_PACKET ? 1 : 0;
+#else
+	errno = EAFNOSUPPORT;
+	return -1;
+#endif
+}
+
+socklen_t
 sa_len(const struct sockaddr *sa)
 {
 #ifdef BSD
 	return sa->sa_len;
 #else
 	switch (sa->sa_family) {
+#ifdef AF_PACKET
+	case AF_PACKET:
+		return sizeof(struct sockaddr_ll);
+#endif
 	case AF_INET:
 		return sizeof(struct sockaddr_in);
 	case AF_INET6:

src/common.h

@@ -49,6 +49,13 @@
 #define UNUSED(a)     (void)(a)
 #define ARRAYCOUNT(a) (sizeof((a)) / sizeof((a)[0]))
 
+#ifndef ALIGNBYTES
+#define ALIGNBYTES (sizeof(int) - 1)
+#endif
+#ifndef ALIGN
+#define ALIGN(p) (((unsigned int)(p) + ALIGNBYTES) & ~ALIGNBYTES)
+#endif
+
 /* Some systems don't define timespec macros */
 #ifndef timespecclear
 #define timespecclear(tsp) (tsp)->tv_sec = (time_t)((tsp)->tv_nsec = 0L)
@@ -100,7 +107,8 @@ uint8_t inet_ntocidr(struct in_addr *);
 
 struct sockaddr;
 
-size_t sa_len(const struct sockaddr *);
+int sa_is_link(const struct sockaddr *);
+socklen_t sa_len(const struct sockaddr *);
 int sa_cmp(const struct sockaddr *, const struct sockaddr *);
 #define ss_len(ss) sa_len((const struct sockaddr *)(ss))
 int sa_pton(struct sockaddr *, const char *restrict);