diff --git a/src/lib/net/address.h b/src/lib/net/address.h
index 5ab654ef1d..6b18919f6d 100644
--- a/src/lib/net/address.h
+++ b/src/lib/net/address.h
@@ -95,6 +95,7 @@ static inline uint32_t tor_addr_to_ipv4n(const tor_addr_t *a);
 static inline uint32_t tor_addr_to_ipv4h(const tor_addr_t *a);
 static inline uint32_t tor_addr_to_mapped_ipv4h(const tor_addr_t *a);
 static inline sa_family_t tor_addr_family(const tor_addr_t *a);
+static inline bool tor_addr_is_unspec(const tor_addr_t *a);
 static inline const struct in_addr *tor_addr_to_in(const tor_addr_t *a);
 static inline int tor_addr_eq_ipv4h(const tor_addr_t *a, uint32_t u);
 
@@ -188,6 +189,15 @@ tor_addr_family(const tor_addr_t *a)
   return a->family;
 }
 
+/**
+ * Return true if the address @a is in the UNSPEC family.
+ **/
+static inline bool
+tor_addr_is_unspec(const tor_addr_t *a)
+{
+  return a->family == AF_UNSPEC;
+}
+
 /** Return an in_addr* equivalent to <b>a</b>, or NULL if <b>a</b> is not
  * an IPv4 address. */
 static inline const struct in_addr *