Revision 26:e5cfc2628e84, committed 2019-04-15

Comitter:

ccli8

Date:

Mon Apr 15 17:31:56 2019 +0800

Parent:

25:edf568984d27

Child:

27:b12add202b88

Commit message:

Reduce memory footprint according to RFC 6066 TLS extension

1. Enable RFC 6066 max_fragment_length extension.
2. Reduce `MBEDTLS_SSL_IN_CONTENT_LEN`/`MBEDTLS_SSL_OUT_CONTENT_LEN` to 4KiB/4KiB from 16KiB/16KiB.

But this approach is risky because:
1. AWS IoT doesn't support RFC 6066 TLS extension yet.
2. TLS handshake may need larger I/O buffers than configured 4KiB/4KiB. 4KiB/4KiB is minimum
to pass TLS handshake per test.

Changed in this revision

--- a/README.md	Mon Apr 15 15:40:16 2019 +0800
+++ b/README.md	Mon Apr 15 17:31:56 2019 +0800
@@ -307,4 +307,27 @@
             <b>"ESP8266_MISC_TIMEOUT=5000"</b>
         ],
         "config": {
-    </pre>
\ No newline at end of file
+    </pre>
+    
+-   Reduce memory footprint according to RFC 6066 TLS extension
+    `MBEDTLS_SSL_IN_CONTENT_LEN`/`MBEDTLS_SSL_OUT_CONTENT_LEN` determine the sizes of incoming/outgoing TLS I/O buffers.
+    We reduce the sizes by default according to RFC 6066:
+    1. Enable RFC 6066 max_fragment_length extension.
+    1. Reduce `MBEDTLS_SSL_IN_CONTENT_LEN`/`MBEDTLS_SSL_OUT_CONTENT_LEN` to 4KiB/4KiB from 16KiB/16KiB.
+
+    But this approach is risky because:
+    1. AWS IoT doesn't support RFC 6066 TLS extension yet.
+    1. TLS handshake may need larger I/O buffers than configured 4KiB/4KiB.
+
+    If you doubt your trouble is caused by this configuration, disable it by:
+    1.  Remove the line `my-tlssocket.tls-max-frag-len` in `mbed_app.json`.
+        ```json
+        "NUMAKER_PFM_NUC472": {
+            "target.network-default-interface-type" : "ETHERNET",
+            "target.macros_add": [
+                "ESP8266_AT_SEL=ESP8266_AT_EXTERN"
+            ]
+        },
+        ```
+    1.  Comment out `MBEDTLS_SSL_IN_CONTENT_LEN`/`MBEDTLS_SSL_OUT_CONTENT_LEN` in `mbedtls_user_config.h`.
+        This will change back to 16KiB/16KiB.

--- a/mbed_app.json	Mon Apr 15 15:40:16 2019 +0800
+++ b/mbed_app.json	Mon Apr 15 17:31:56 2019 +0800
@@ -18,21 +18,18 @@
         },
         "NUMAKER_PFM_NUC472": {
             "target.network-default-interface-type" : "ETHERNET",
-            "target.macros_add": [
-                "ESP8266_AT_SEL=ESP8266_AT_EXTERN"
-            ]
+            "my-tlssocket.tls-max-frag-len"         : 4,
+            "target.macros_add"                     : ["ESP8266_AT_SEL=ESP8266_AT_EXTERN"]
         },
         "NUMAKER_PFM_M487": {
             "target.network-default-interface-type" : "ETHERNET",
-            "target.macros_add": [
-                "ESP8266_AT_SEL=ESP8266_AT_EXTERN"
-            ]
+            "my-tlssocket.tls-max-frag-len"         : 4,
+            "target.macros_add"                     : ["ESP8266_AT_SEL=ESP8266_AT_EXTERN"]
         },
         "NUMAKER_IOT_M487": {
             "target.network-default-interface-type" : "WIFI",
-            "target.macros_add": [
-                "ESP8266_AT_SEL=ESP8266_AT_ONBOARD"
-            ]
+            "my-tlssocket.tls-max-frag-len"         : 4,
+            "target.macros_add"                     : ["ESP8266_AT_SEL=ESP8266_AT_ONBOARD"]
         }
     }
 }

--- a/mbedtls_user_config.h	Mon Apr 15 15:40:16 2019 +0800
+++ b/mbedtls_user_config.h	Mon Apr 15 17:31:56 2019 +0800
@@ -42,7 +42,7 @@
 #endif /* TARGET_STM32F439xI && MBEDTLS_CONFIG_HW_SUPPORT */
 
 /* Maximum length (in bytes) of incoming plaintext fragments */
-//#define MBEDTLS_SSL_IN_CONTENT_LEN      4096
+#define MBEDTLS_SSL_IN_CONTENT_LEN      4096
 
 /* Maximum length (in bytes) of outgoing plaintext fragments */
-//#define MBEDTLS_SSL_OUT_CONTENT_LEN     4096
+#define MBEDTLS_SSL_OUT_CONTENT_LEN     4096