1 files changed, 22 insertions, 0 deletions
diff --git a/src/tool/server.cc b/src/tool/server.cc
index 3b125ad1..4cc183b1 100644
--- a/src/tool/server.cc
+++ b/src/tool/server.cc
@@ -71,6 +71,10 @@ static const struct argument kArguments[] = {
         "-tls13-variant", kBooleanArgument, "Enable TLS 1.3 variants",
     },
     {
+        "-debug", kBooleanArgument,
+        "Print debug information about the handshake",
+    },
+    {
         "", kOptionalArgument, "",
     },
 };
@@ -142,6 +146,20 @@ static bssl::UniquePtr<X509> MakeSelfSignedCert(EVP_PKEY *evp_pkey,
   return x509;
 }
 
+static void InfoCallback(const SSL *ssl, int type, int value) {
+  switch (type) {
+    case SSL_CB_HANDSHAKE_START:
+      fprintf(stderr, "Handshake started.\n");
+      break;
+    case SSL_CB_HANDSHAKE_DONE:
+      fprintf(stderr, "Handshake done.\n");
+      break;
+    case SSL_CB_ACCEPT_LOOP:
+      fprintf(stderr, "Handshake progress: %s\n", SSL_state_string_long(ssl));
+      break;
+  }
+}
+
 bool Server(const std::vector<std::string> &args) {
   if (!InitSocketLibrary()) {
     return false;
@@ -241,6 +259,10 @@ bool Server(const std::vector<std::string> &args) {
     SSL_CTX_set_tls13_variant(ctx.get(), tls13_experiment);
   }
 
+  if (args_map.count("-debug") != 0) {
+    SSL_CTX_set_info_callback(ctx.get(), InfoCallback);
+  }
+
   Listener listener;
   if (!listener.Init(args_map["-accept"])) {
     return false;