snap_start_tests: test NPN misprediction.

net/test/openssl_helper.cc

Index: net/test/openssl_helper.cc
diff --git a/net/test/openssl_helper.cc b/net/test/openssl_helper.cc
index b3eb20fd3e557864bab7bf745f7fb0b04d5ea0e4..25989cb60166607e0f67e01e176df506b0a2e157 100644
--- a/net/test/openssl_helper.cc
+++ b/net/test/openssl_helper.cc
@@ -30,9 +30,19 @@ static int verify_cb(int preverify_ok, X509_STORE_CTX *ctx) {
 // Next Protocol Negotiation callback from OpenSSL
 static int next_proto_cb(SSL *ssl, const unsigned char **out,
                          unsigned int *outlen, void *arg) {
+  bool* npn_mispredict = reinterpret_cast<bool*>(arg);
   static char kProtos[] = "\003foo\003bar";
-  *out = (const unsigned char*) kProtos;
-  *outlen = sizeof(kProtos) - 1;
+  static char kProtos2[] = "\003baz\003boo";
+  static unsigned count = 0;
+
+  if (!*npn_mispredict || count == 0) {
+    *out = (const unsigned char*) kProtos;
+    *outlen = sizeof(kProtos) - 1;
+  } else {
+    *out = (const unsigned char*) kProtos2;
+    *outlen = sizeof(kProtos2) - 1;
+  }
+  count++;
   return SSL_TLSEXT_ERR_OK;
 }
 
@@ -46,6 +56,7 @@ main(int argc, char **argv) {
   bool sni = false, sni_good = false, snap_start = false;
   bool snap_start_recovery = false, sslv3 = false, session_tickets = false;
   bool fail_resume = false, client_cert = false, npn = false;
+  bool npn_mispredict = false;
 
   const char* key_file = kDefaultPEMFile;
   const char* cert_file = kDefaultPEMFile;
@@ -76,6 +87,10 @@ main(int argc, char **argv) {
     } else if (strcmp(argv[i], "npn") == 0) {
       // Advertise NPN
       npn = true;
+    } else if (strcmp(argv[i], "npn-mispredict") == 0) {
+      // Advertise NPN
+      npn = true;
+      npn_mispredict = true;
     } else if (strcmp(argv[i], "--key-file") == 0) {
       // Use alternative key file
       i++;
@@ -165,11 +180,13 @@ main(int argc, char **argv) {
   }
 
   if (npn)
-    SSL_CTX_set_next_protos_advertised_cb(ctx, next_proto_cb, NULL);
+    SSL_CTX_set_next_protos_advertised_cb(ctx, next_proto_cb, &npn_mispredict);
 
   unsigned connection_limit = 1;
   if (snap_start || session_tickets)
     connection_limit = 2;
+  if (npn_mispredict)
+    connection_limit = 3;
 
   for (unsigned connections = 0; connections < connection_limit;
        connections++) {
@@ -209,10 +226,17 @@ main(int argc, char **argv) {
     }
 
     if (npn) {
-      const unsigned char *data;
-      unsigned len;
+      const unsigned char *data, *expected_data;
+      unsigned len, expected_len;
       SSL_get0_next_proto_negotiated(server, &data, &len);
-      if (len != 3 || memcmp(data, "bar", 3) != 0) {
+      if (!npn_mispredict || connections == 0) {
+        expected_data = (unsigned char*) "foo";
+        expected_len = 3;
+      } else {
+        expected_data = (unsigned char*) "baz";
+        expected_len = 3;
+      }
+      if (len != expected_len || memcmp(data, expected_data, len) != 0) {
         fprintf(stderr, "Bad NPN: %d\n", len);
         return 1;
       }