diff --git a/lib/in46_addr.c b/lib/in46_addr.c
new file mode 100644
index 0000000..903ceec
--- /dev/null
+++ b/lib/in46_addr.c
@@ -0,0 +1,148 @@
+/*
+ * IPv4/v6 address functions.
+ * Copyright (C) 2017 by Harald Welte <laforge@gnumonks.org>
+ *
+ * The contents of this file may be used under the terms of the GNU
+ * General Public License Version 2, provided that the above copyright
+ * notice and this permission notice is included in all copies or
+ * substantial portions of the software.
+ * 
+ */
+
+#include "../lib/in46_addr.h"
+
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <string.h>
+
+/*! Return the address family of given \reff in46_addr argument */
+int in46a_to_af(const struct in46_addr *in)
+{
+	switch (in->len) {
+	case 4:
+		return AF_INET;
+	case 16:
+		return AF_INET6;
+	default:
+		return -1;
+	}
+}
+
+/*! Convert \ref in46_addr to sockaddr_storage */
+int in46a_to_sas(struct sockaddr_storage *out, const struct in46_addr *in)
+{
+	struct sockaddr_in *sin = (struct sockaddr_in *)out;
+	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)out;
+
+	switch (in->len) {
+	case 4:
+		sin->sin_family = AF_INET;
+		sin->sin_addr = in->v4;
+		break;
+	case 16:
+		sin6->sin6_family = AF_INET;
+		sin6->sin6_addr = in->v6;
+		break;
+	default:
+		return -1;
+	}
+
+	return 0;
+}
+
+/*! Convenience wrapper around inet_ntop() for \ref in46_addr */
+const char *in46a_ntop(const struct in46_addr *in, char *dst, socklen_t dst_size)
+{
+	int af = in46a_to_af(in);
+	if (af < 0)
+		return NULL;
+
+	return inet_ntop(af, (const void *) &in->v4, dst, dst_size);
+}
+
+/*! Determine if two in46_addr are equal or not
+ *  \returns 1 in case they are equal; 0 otherwise */
+int in46a_equal(const struct in46_addr *a, const struct in46_addr *b)
+{
+	if (a->len == b->len && !memcmp(&a->v6, &b->v6, a->len))
+		return 1;
+	else
+		return 0;
+}
+
+/*! Match if IPv6 addr1 + addr2 are within same \a mask */
+static int ipv6_within_mask(const struct in6_addr *addr1, const struct in6_addr *addr2,
+			    const struct in6_addr *mask)
+{
+	struct in6_addr masked = *addr2;
+#if defined(__linux__)
+	masked.s6_addr32[0] &= mask->s6_addr32[0];
+	masked.s6_addr32[1] &= mask->s6_addr32[1];
+	masked.s6_addr32[2] &= mask->s6_addr32[2];
+	masked.s6_addr32[3] &= mask->s6_addr32[3];
+#else
+	masked.__u6_addr.__u6_addr32[0] &= mask->__u6_addr.__u6_addr32[0];
+	masked.__u6_addr.__u6_addr32[1] &= mask->__u6_addr.__u6_addr32[1];
+	masked.__u6_addr.__u6_addr32[2] &= mask->__u6_addr.__u6_addr32[2];
+	masked.__u6_addr.__u6_addr32[3] &= mask->__u6_addr.__u6_addr32[3];
+#endif
+	if (!memcmp(addr1, &masked, sizeof(struct in6_addr)))
+		return 1;
+	else
+		return 0;
+}
+
+/*! Create an IPv6 netmask from the given prefix length */
+static void create_ipv6_netmask(struct in6_addr *netmask, int prefixlen)
+{
+	uint32_t *p_netmask;
+	memset(netmask, 0, sizeof(struct in6_addr));
+	if (prefixlen < 0)
+		prefixlen = 0;
+	else if (128 < prefixlen)
+		prefixlen = 128;
+
+#if defined(__linux__)
+	p_netmask = &netmask->s6_addr32[0];
+#else
+	p_netmask = &netmask->__u6_addr.__u6_addr32[0];
+#endif
+	while (32 < prefixlen) {
+		*p_netmask = 0xffffffff;
+		p_netmask++;
+		prefixlen -= 32;
+	}
+	if (prefixlen != 0) {
+		*p_netmask = htonl(0xFFFFFFFF << (32 - prefixlen));
+	}
+}
+
+/*! Determine if given \a addr is within given \a net + \a prefixlen
+ *  Builds the netmask from \a net + \a prefixlen and matches it to \a addr
+ *  \returns 1 in case of a match, 0 otherwise */
+int in46a_within_mask(const struct in46_addr *addr, const struct in46_addr *net, size_t prefixlen)
+{
+	struct in_addr netmask;
+	struct in6_addr netmask6;
+
+	if (addr->len != net->len)
+		return 0;
+
+	switch (addr->len) {
+	case 4:
+		netmask.s_addr = htonl(0xFFFFFFFF << (32 - prefixlen));
+		if ((addr->v4.s_addr & netmask.s_addr) == net->v4.s_addr)
+			return 1;
+		else
+			return 0;
+	case 16:
+		create_ipv6_netmask(&netmask6, prefixlen);
+		return ipv6_within_mask(&addr->v6, &net->v6, &netmask6);
+	default:
+		return 0;
+	}
+}