Add support for DTLS fragmentation

Author: mickel8

bundlex.exs

@@ -10,12 +10,12 @@ defmodule ExDTLS.BundlexProject do
   defp natives() do
     [
       native: [
-        sources: ["native.c", "dtls.c", "dyn_buff.c"],
+        sources: ["native.c", "dtls.c", "dyn_buff.c", "bio_frag.c"],
         deps: [unifex: :unifex],
         os_deps: [openssl: :pkg_config],
         libs: ["pthread"],
         interface: [:nif],
-        # compiler_flags: ["-DEXDTLS_DEBUG"],
+        compiler_flags: ["-DEXDTLS_DEBUG"],
         preprocessor: Unifex
       ]
     ]

c_src/ex_dtls/bio_frag.c

@@ -0,0 +1,98 @@
+
+#include "bio_frag.h"
+
+static int bwrite(BIO *bio, const char *buf, int len);
+static int bread(BIO *bio, char *buf, int len);
+static long ctrl(BIO *bio, int cmd, long arg1, void *arg2);
+static int create(BIO *bio);
+static int destroy(BIO *bio);
+static long callback_ctrl(BIO *bio, int cmd, BIO_info_cb *fp);
+
+// static const BIO_METHOD bio_methods = {
+//   BIO_TYPE_BIO,
+//   "DTLS fragmentation for mem BIO",
+//   bwrite_conv,
+//   bwrite,
+//   bread_conv,
+//   bread,
+//   NULL,
+//   NULL,
+//   ctrl,
+//   create,
+//   destroy,
+//   callback_ctrl
+// };
+
+static BIO_METHOD *bio_methods = NULL;
+
+const BIO_METHOD *BIO_f_frag(void) {
+  bio_methods = BIO_meth_new(BIO_TYPE_FILTER, "DTLS fragmentation for mem BIO");
+
+  BIO_meth_set_read(bio_methods, bread);
+  BIO_meth_set_write(bio_methods, bwrite);
+  BIO_meth_set_ctrl(bio_methods, ctrl);
+  BIO_meth_set_create(bio_methods, create);
+  BIO_meth_set_destroy(bio_methods, destroy);
+  BIO_meth_set_callback_ctrl(bio_methods, callback_ctrl);
+
+  return bio_methods;
+}
+
+static int create(BIO *bio) {
+  DEBUG("BIO frag create");
+  // indicate that BIO initialization is complete 
+  BIO_set_init(bio, 1);
+  return 1;
+}
+
+static int destroy(BIO *bio) {
+  DEBUG("BIO frag destroy");
+  if (bio == NULL) {
+    return 0;
+  }
+
+  BIO_set_init(bio, 0);
+  return 1;
+}
+
+static int bread(BIO *bio, char *buf, int len) {
+  DEBUG("BIO frag bread");
+  BIO *next = BIO_next(bio);
+  if (next == NULL) {
+    return 0;
+  }
+
+  return BIO_read(next, buf, len);
+}
+
+static int bwrite(BIO *bio, const char *buf, int len) {
+  DEBUG("BIO frag bwrite %d", len);
+  BIO *next = BIO_next(bio);
+  if (next == NULL) {
+    return 0;
+  }
+
+  return BIO_write(next, buf, len);
+}
+
+static long ctrl(BIO *bio, int cmd, long num, void *ptr) {
+  DEBUG("BIO frag ctrl");
+
+  BIO *next = BIO_next(bio);
+  if (next == NULL) {
+    return 0;
+  }
+
+  return BIO_ctrl(next, cmd, num, ptr);
+}
+
+static long callback_ctrl(BIO *bio, int cmd, BIO_info_cb *fp) {
+  BIO *next = BIO_next(bio);
+  if (next == NULL) {
+    return 0;
+  }
+
+  return BIO_callback_ctrl(next, cmd, fp);
+}
+
+

c_src/ex_dtls/bio_frag.h

@@ -0,0 +1,7 @@
+#include <openssl/opensslv.h>
+#include <openssl/err.h>
+#include <openssl/ssl.h>
+
+#include "log.h"
+
+const BIO_METHOD *BIO_f_frag(void);

c_src/ex_dtls/dtls.c

@@ -1,5 +1,7 @@
 #include "dtls.h"
 
+#include "bio_frag.h"
+
 SSL_CTX *create_ctx(int dtls_srtp) {
   SSL_CTX *ssl_ctx = SSL_CTX_new(DTLS_method());
   if (ssl_ctx == NULL) {
@@ -33,19 +35,33 @@ SSL *create_ssl(SSL_CTX *ssl_ctx, int mode) {
     return NULL;
   }
 
-  BIO *rbio = BIO_new(BIO_s_mem());
-  if (rbio == NULL) {
-    DEBUG("Cannot create rbio");
+  BIO *frag_bio = BIO_new(BIO_f_frag());
+  if (frag_bio == NULL) {
+    DEBUG("Cannot create frag bio");
     return NULL;
   }
 
-  BIO *wbio = BIO_new(BIO_s_mem());
-  if (wbio == NULL) {
-    DEBUG("Cannot create wbio");
+  BIO *wmem_bio = BIO_new(BIO_s_mem());
+  if (wmem_bio == NULL) {
+    DEBUG("Cannot create write mem bio");
+    return NULL;
+  }
+
+  BIO *wchain = BIO_push(frag_bio, wmem_bio);
+
+  BIO *rmem_bio = BIO_new(BIO_s_mem());
+  if (rmem_bio == NULL) {
+    DEBUG("Cannot create read mem bio");
     return NULL;
   }
 
-  SSL_set_bio(ssl, rbio, wbio);
+  SSL_set_bio(ssl, rmem_bio, wchain);
+  
+  // printf("Setting MTU to 1000\n");
+  // if (SSL_set_mtu(ssl, 1500) == 0) {
+  //   return NULL;
+  // } 
+  
 
   return ssl;
 }

test/integration_test.exs

@@ -1,6 +1,7 @@
 defmodule ExDTLS.IntegrationTest do
   use ExUnit.Case, async: true
 
+  @tag :debug
   test "dtls_srtp" do
     rx_dtls = ExDTLS.init(mode: :server, dtls_srtp: true, verify_peer: true)
     tx_dtls = ExDTLS.init(mode: :client, dtls_srtp: true, verify_peer: true)