diff --git a/crypto/bio/bio.h b/crypto/bio/bio.h
index 8489ff80bb033e9417c7a88c8707074b60d46491..122ec04e0b817a5cc5d298112ae2d6e07ab0b120 100644
--- a/crypto/bio/bio.h
+++ b/crypto/bio/bio.h
@@ -176,6 +176,8 @@ extern "C" {
                                               * adjust socket timeouts */
 #define BIO_CTRL_DGRAM_SET_DONT_FRAG      48
 
+#define BIO_CTRL_DGRAM_GET_MTU_OVERHEAD   49
+
 #ifndef OPENSSL_NO_SCTP
 /* SCTP stuff */
 #define BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE	50
@@ -608,6 +610,8 @@ int BIO_ctrl_reset_read_request(BIO *b);
          (int)BIO_ctrl(b, BIO_CTRL_DGRAM_GET_PEER, 0, (char *)peer)
 #define BIO_dgram_set_peer(b,peer) \
          (int)BIO_ctrl(b, BIO_CTRL_DGRAM_SET_PEER, 0, (char *)peer)
+#define BIO_dgram_get_mtu_overhead(b) \
+         (unsigned int)BIO_ctrl((b), BIO_CTRL_DGRAM_GET_MTU_OVERHEAD, 0, NULL)
 
 /* These two aren't currently implemented */
 /* int BIO_get_ex_num(BIO *bio); */
diff --git a/crypto/bio/bss_dgram.c b/crypto/bio/bss_dgram.c
index 8a1eb6de8b2357a372b954830692aa026ff5f7d8..bf1e39b5c0b4009dd7bb26ffbe3b1a24984cd893 100644
--- a/crypto/bio/bss_dgram.c
+++ b/crypto/bio/bss_dgram.c
@@ -458,6 +458,36 @@ static int dgram_write(BIO *b, const char *in, int inl)
 	return(ret);
 	}
 
+static long dgram_get_mtu_overhead(bio_dgram_data *data)
+	{
+	long ret;
+
+	switch (data->peer.sa.sa_family)
+		{
+		case AF_INET:
+			/* Assume this is UDP - 20 bytes for IP, 8 bytes for UDP */
+			ret = 28;
+			break;
+#if OPENSSL_USE_IPV6
+		case AF_INET6:
+#ifdef IN6_IS_ADDR_V4MAPPED
+			if (IN6_IS_ADDR_V4MAPPED(&data->peer.sa_in6.sin6_addr))
+				/* Assume this is UDP - 20 bytes for IP, 8 bytes for UDP */
+				ret = 28;
+			else
+#endif
+				/* Assume this is UDP - 40 bytes for IP, 8 bytes for UDP */
+				ret = 48;
+			break;
+#endif
+		default:
+			/* We don't know. Go with the historical default */
+			ret = 28;
+			break;
+		}
+	return ret;
+	}
+
 static long dgram_ctrl(BIO *b, int cmd, long num, void *ptr)
 	{
 	long ret=1;
@@ -634,23 +664,24 @@ static long dgram_ctrl(BIO *b, int cmd, long num, void *ptr)
 #endif
 		break;
 	case BIO_CTRL_DGRAM_GET_FALLBACK_MTU:
+		ret = -dgram_get_mtu_overhead(data);
 		switch (data->peer.sa.sa_family)
 			{
 			case AF_INET:
-				ret = 576 - 20 - 8;
+				ret += 576;
 				break;
 #if OPENSSL_USE_IPV6
 			case AF_INET6:
 #ifdef IN6_IS_ADDR_V4MAPPED
 				if (IN6_IS_ADDR_V4MAPPED(&data->peer.sa_in6.sin6_addr))
-					ret = 576 - 20 - 8;
+					ret += 576;
 				else
 #endif
-					ret = 1280 - 40 - 8;
+					ret += 1280;
 				break;
 #endif
 			default:
-				ret = 576 - 20 - 8;
+				ret += 576;
 				break;
 			}
 		break;
@@ -895,6 +926,9 @@ static long dgram_ctrl(BIO *b, int cmd, long num, void *ptr)
 				break;
 			}
 		break;
+	case BIO_CTRL_DGRAM_GET_MTU_OVERHEAD:
+		ret = dgram_get_mtu_overhead(data);
+		break;
 	default:
 		ret=0;
 		break;
@@ -1415,6 +1449,10 @@ static long dgram_sctp_ctrl(BIO *b, int cmd, long num, void *ptr)
 		 * Returns always 1.
 		 */
 		break;
+	case BIO_CTRL_DGRAM_GET_MTU_OVERHEAD:
+		/* We allow transport protocol fragmentation so this is irrelevant */
+		ret = 0;
+		break;
 	case BIO_CTRL_DGRAM_SCTP_SET_IN_HANDSHAKE:
 		if (num > 0)
 			data->in_handshake = 1;