diff --git a/CHANGELOG b/CHANGELOG
index 180cb405..666ae700 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -20,7 +20,11 @@ HISTORY
   ++ New features:
 
   2010-02-08: Simon Goldschmidt
-  * netif.h: Added 
+  * inet.h, ip_addr.c/.h: Added reentrant versions of inet_ntoa/ipaddr_ntoa
+    inet_ntoa_r/ipaddr_ntoa_r
+
+  2010-02-08: Simon Goldschmidt
+  * netif.h: Added netif_s/get_igmp_mac_filter() macros
 
   2010-02-05: Simon Goldschmidt
   * netif.h: Added function-like macros to get/set the hostname on a netif
diff --git a/src/core/ipv4/ip_addr.c b/src/core/ipv4/ip_addr.c
index e54c6f76..c4bcdf73 100644
--- a/src/core/ipv4/ip_addr.c
+++ b/src/core/ipv4/ip_addr.c
@@ -223,6 +223,20 @@ char *
 ipaddr_ntoa(ip_addr_t *addr)
 {
   static char str[16];
+  return ipaddr_ntoa_r(addr, str, 16);
+}
+
+/**
+ * Same as ipaddr_ntoa, but reentrant since a user-supplied buffer is used.
+ *
+ * @param addr ip address in network order to convert
+ * @param buf target buffer where the string is stored
+ * @param buflen length of buf
+ * @return either pointer to buf which now holds the ASCII
+ *         representation of addr or NULL if buf was too small
+ */
+char *ipaddr_ntoa_r(ip_addr_t *addr, char *buf, int buflen)
+{
   u32_t s_addr;
   char inv[3];
   char *rp;
@@ -230,10 +244,11 @@ ipaddr_ntoa(ip_addr_t *addr)
   u8_t rem;
   u8_t n;
   u8_t i;
+  int len = 0;
 
   s_addr = ip4_addr_get_u32(addr);
 
-  rp = str;
+  rp = buf;
   ap = (u8_t *)&s_addr;
   for(n = 0; n < 4; n++) {
     i = 0;
@@ -242,11 +257,18 @@ ipaddr_ntoa(ip_addr_t *addr)
       *ap /= (u8_t)10;
       inv[i++] = '0' + rem;
     } while(*ap);
-    while(i--)
+    while(i--) {
+      if (len++ >= buflen) {
+        return NULL;
+      }
       *rp++ = inv[i];
+    }
+    if (len++ >= buflen) {
+      return NULL;
+    }
     *rp++ = '.';
     ap++;
   }
   *--rp = 0;
-  return str;
-}
\ No newline at end of file
+  return buf;
+}
diff --git a/src/include/ipv4/lwip/inet.h b/src/include/ipv4/lwip/inet.h
index 640608fc..cb33486b 100644
--- a/src/include/ipv4/lwip/inet.h
+++ b/src/include/ipv4/lwip/inet.h
@@ -96,6 +96,7 @@ struct in_addr {
 #define inet_addr(cp)         ipaddr_addr(cp)
 #define inet_aton(cp, addr)   ipaddr_aton(cp, (ip_addr_t*)addr)
 #define inet_ntoa(addr)       ipaddr_ntoa((ip_addr_t*)&(addr))
+#define inet_ntoa_r(addr, buf, buflen) ipaddr_ntoa_r((ip_addr_t*)&(addr), buf, buflen)
 
 #ifdef __cplusplus
 }
diff --git a/src/include/ipv4/lwip/ip_addr.h b/src/include/ipv4/lwip/ip_addr.h
index afe2a8ac..e84c3e78 100644
--- a/src/include/ipv4/lwip/ip_addr.h
+++ b/src/include/ipv4/lwip/ip_addr.h
@@ -204,6 +204,7 @@ u32_t ipaddr_addr(const char *cp);
 int ipaddr_aton(const char *cp, ip_addr_t *addr);
 /** returns ptr to static buffer; not reentrant! */
 char *ipaddr_ntoa(ip_addr_t *addr);
+char *ipaddr_ntoa_r(ip_addr_t *addr, char *buf, int buflen);
 
 #ifdef __cplusplus
 }