There are a number of instances throughout the code where the constant 28 is
[openssl.git] / crypto / bio / bss_dgram.c
index 8a1eb6d..bf1e39b 100644 (file)
@@ -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;