diff --git a/sys/src/cmd/ip/dhcpd/dat.h b/sys/src/cmd/ip/dhcpd/dat.h
index 80052674b..a2062fc95 100644
--- a/sys/src/cmd/ip/dhcpd/dat.h
+++ b/sys/src/cmd/ip/dhcpd/dat.h
@@ -49,8 +49,6 @@ struct Info
 
 
 /* from dhcp.c */
-extern int	validip(uchar*);
-extern int	validipmask(uchar*);
 extern void	fatal(char*, ...);
 extern void	warning(char*, ...);
 #pragma	varargck argpos	fatal 1
@@ -58,6 +56,8 @@ extern void	warning(char*, ...);
 extern int	minlease;
 
 /* from db.c */
+extern int	validip(uchar*);
+extern int	validipmask(uchar*);
 extern char*	toid(uchar*, int);
 extern void	initbinding(uchar*, int);
 extern Binding*	iptobinding(uchar*, int);
diff --git a/sys/src/cmd/ip/dhcpd/db.c b/sys/src/cmd/ip/dhcpd/db.c
index 80d072ed6..d20a5a4bd 100644
--- a/sys/src/cmd/ip/dhcpd/db.c
+++ b/sys/src/cmd/ip/dhcpd/db.c
@@ -412,3 +412,22 @@ releasebinding(Binding *b, char *id)
 	close(fd);
 	return 0;
 }
+
+int
+validip(uchar *ip)
+{
+	if(ipcmp(ip, v4prefix) == 0)
+		return 0;
+	return isv4(ip);
+}
+
+int
+validipmask(uchar *mask)
+{
+	unsigned x;
+
+	if(memcmp(mask, IPallbits, IPv4off) != 0)
+		return 0;
+	x = ~(mask[IPv4off+0] << 24 | mask[IPv4off+1] << 16 | mask[IPv4off+2] << 8 | mask[IPv4off+3]);
+	return ((x + 1U) & x) == 0;
+}
diff --git a/sys/src/cmd/ip/dhcpd/dhcpd.c b/sys/src/cmd/ip/dhcpd/dhcpd.c
index 22a60b584..8c6727a6a 100644
--- a/sys/src/cmd/ip/dhcpd/dhcpd.c
+++ b/sys/src/cmd/ip/dhcpd/dhcpd.c
@@ -191,7 +191,6 @@ void	sendnak(Req*, uchar*, char*);
 void	sendoffer(Req*, uchar*, int);
 void	stringopt(Req*, int, char*);
 void	termopt(Req*);
-int	validip(uchar*);
 void	vectoropt(Req*, int, uchar*, int);
 
 void
@@ -1389,26 +1388,6 @@ readsysname(void)
 	return p;
 }
 
-extern int
-validip(uchar *ip)
-{
-	if(ipcmp(ip, IPnoaddr) == 0)
-		return 0;
-	if(ipcmp(ip, v4prefix) == 0)
-		return 0;
-	return isv4(ip);
-}
-
-extern int
-validipmask(uchar *ip)
-{
-	if(ipcmp(ip, IPnoaddr) == 0)
-		return 0;
-	if(ipcmp(ip, v4prefix) == 0)
-		return 0;
-	return 1;
-}
-
 void
 longopt(Req *rp, int t, long v)
 {
diff --git a/sys/src/cmd/ip/dhcpd/dhcpleases.c b/sys/src/cmd/ip/dhcpd/dhcpleases.c
index 7e027923d..fffcfd39a 100644
--- a/sys/src/cmd/ip/dhcpd/dhcpleases.c
+++ b/sys/src/cmd/ip/dhcpd/dhcpleases.c
@@ -35,7 +35,9 @@ main(void)
 	b.lease = b.offer = 0;
 	now = time(0);
 	for(i = 0; i < nall; i++){
-		if(parseip(b.ip, all[i].name) == -1 || syncbinding(&b, 0) < 0)
+		if(parseip(b.ip, all[i].name) == -1
+		|| !validip(b.ip)
+		|| syncbinding(&b, 0) < 0)
 			continue;
 		if(b.lease > now)
 			print("%I leased by %s until %s", b.ip, b.boundto,
diff --git a/sys/src/cmd/ip/dhcpd/ndb.c b/sys/src/cmd/ip/dhcpd/ndb.c
index da0244868..91fb1751c 100644
--- a/sys/src/cmd/ip/dhcpd/ndb.c
+++ b/sys/src/cmd/ip/dhcpd/ndb.c
@@ -57,19 +57,19 @@ localip(uchar *laddr, uchar *raddr, Ipifc *ifc)
 }
 
 static void
-setipaddr(uchar *addr, char *ip)
+setipaddr(uchar *ip, char *s)
 {
-	if(ipcmp(addr, IPnoaddr) == 0)
-		if(parseip(addr, ip) == -1
-		|| !validip(addr))
-			ipmove(addr, IPnoaddr);	/* invalid */
+	if(ipcmp(ip, IPnoaddr) == 0)
+		if(parseip(ip, s) == -1
+		|| !validip(ip))
+			ipmove(ip, IPnoaddr);	/* invalid */
 }
 
 static void
-setipmask(uchar *mask, char *ip)
+setipmask(uchar *mask, char *s)
 {
 	if(ipcmp(mask, IPnoaddr) == 0)
-		if(parseipmask(mask, ip, 1) == -1
+		if(parseipmask(mask, s, 1) == -1
 		|| !validipmask(mask))
 			ipmove(mask, IPnoaddr);	/* invalid */
 }