2 files changed, 7 insertions, 0 deletions
diff --git a/src/shared/in-addr-util.c b/src/shared/in-addr-util.c
index 459f846173..457eedd6d8 100644
--- a/src/shared/in-addr-util.c
+++ b/src/shared/in-addr-util.c
@@ -242,3 +242,9 @@ int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *re
 
         return -EINVAL;
 }
+
+unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr) {
+        assert(addr);
+
+        return 32 - u32ctz(be32toh(addr->s_addr));
+}
diff --git a/src/shared/in-addr-util.h b/src/shared/in-addr-util.h
index 7d1d6baa27..0036acee22 100644
--- a/src/shared/in-addr-util.h
+++ b/src/shared/in-addr-util.h
@@ -39,6 +39,7 @@ int in_addr_prefix_next(int family, union in_addr_union *u, unsigned prefixlen);
 int in_addr_to_string(int family, const union in_addr_union *u, char **ret);
 int in_addr_from_string(int family, const char *s, union in_addr_union *ret);
 int in_addr_from_string_auto(const char *s, int *family, union in_addr_union *ret);
+unsigned in_addr_netmask_to_prefixlen(const struct in_addr *addr);
 
 static inline size_t FAMILY_ADDRESS_SIZE(int family) {
         assert(family == AF_INET || family == AF_INET6);