diff --git a/util.cpp b/util.cpp
index 5c9b2e2..7561a62 100644
--- a/util.cpp
+++ b/util.cpp
@@ -1,6 +1,7 @@
 #include <cstdio>
 #include <string.h>
 #include <stdarg.h>
+#include <arpa/inet.h>
 
 #include "util.hpp"
 
@@ -17,6 +18,41 @@ void do_debugf(int level, const char *format, ...)
     va_end(args);
 }
 
+const char *
+format_address(const unsigned char *address)
+{
+    static char buf[4][INET6_ADDRSTRLEN];
+    static int i = 0;
+    i = (i + 1) % 4;
+    /*
+    if(v4mapped(address))
+        inet_ntop(AF_INET, address + 12, buf[i], INET6_ADDRSTRLEN);
+    else
+    */
+    inet_ntop(AF_INET6, address, buf[i], INET6_ADDRSTRLEN);
+    return buf[i];
+}
+
+namespace std {
+size_t hash<in6_addr>::operator() (const in6_addr& addr) const {
+    size_t out_hash = 0;
+    for(int i=0; i < 4; ++i) {
+        uint32_t value;
+        memcpy((unsigned char*)(&value),
+               addr.s6_addr + 4*i,
+               4);
+        out_hash ^= (std::hash<uint32_t>{}(value) << 1);
+    }
+    return out_hash;
+}
+
+bool equal_to<in6_addr>::operator()(
+        const in6_addr& lhs, const in6_addr& rhs) const
+{
+    return memcmp(lhs.s6_addr, rhs.s6_addr, sizeof(lhs.s6_addr)) == 0;
+}
+}
+
 MsgException::MsgException(const std::string& msg, int code, bool is_perror)
     : _msg(msg), _code(code)
 {
diff --git a/util.hpp b/util.hpp
index 8f5ad63..8bc5a9e 100644
--- a/util.hpp
+++ b/util.hpp
@@ -2,6 +2,7 @@
 
 #include <exception>
 #include <string>
+#include <netinet/in.h>
 
 /* Debugging -- taken from babeld */
 
@@ -43,6 +44,26 @@ static inline void kdebugf(const char *format, ...) { return; }
 void do_debugf(int level, const char *format, ...);
 
 
+/** format_address -- taken from babeld */
+const char* format_address(const unsigned char* address);
+
+
+/** in6_addr hash & equality */
+namespace std {
+    template<>
+    class hash<in6_addr> {
+        public:
+            size_t operator()(const in6_addr& addr) const;
+    };
+
+    template<>
+    class equal_to<in6_addr> {
+        public:
+            bool operator()(const in6_addr& lhs, const in6_addr& rhs) const;
+    };
+}
+
+
 
 /** MsgException -- an exception bearing a passed explanation message
  *