MXS-1628: Add bad handshake test case

The test checks that a bad handshake error is returned when a malformed
packet is sent.

maxscale-system-test/mxs1628_bad_handshake.cpp

@@ -0,0 +1,71 @@
+#include "testconnections.h"
+#include "tcp_connection.h"
+
+#include <vector>
+
+int main(int argc, char *argv[])
+{
+    TestConnections test(argc, argv);
+    test.set_timeout(30);
+
+    uint32_t caps = 1 | 8 | 512;
+    uint32_t max_packet = 65535;
+    uint8_t charset = 8;
+    std::string username = "username";
+    uint8_t token_len = 20; // SHA1 hash size
+    std::string database = "database";
+
+    // Capabilities, max packet size and client charset
+    std::vector<uint8_t> wbuf;
+    auto it = std::back_inserter(wbuf);
+
+    for (auto a: {(uint8_t)(caps), (uint8_t)(caps >> 8), (uint8_t)(caps >> 16), (uint8_t)(caps >> 24),
+                (uint8_t)(max_packet), (uint8_t)(max_packet >> 8), (uint8_t)(max_packet >> 16), (uint8_t)(max_packet >> 24),
+                charset})
+    {
+        *it++ = a;
+    }
+
+    // Reserved filler space
+    std::fill_n(it, 23, 0);
+
+    // Username without terminating null character
+    for (auto a: username)
+    {
+        *it++ = (uint8_t)a;
+    }
+
+    // Auth token length and the token itself
+    *it++ = token_len;
+    std::fill_n(it, token_len, 123);
+
+    // Database without terminating null character
+    for (auto a: database)
+    {
+        *it++ = (uint8_t)a;
+    }
+
+    // Payload length and sequence number
+    uint8_t bufsize = wbuf.size();
+    wbuf.insert(wbuf.begin(), {(uint8_t)(bufsize), (uint8_t)(bufsize >> 8), (uint8_t)(bufsize >> 16), 2});
+
+
+    tcp::Connection conn;
+    conn.connect(test.maxscale_ip(), test.rwsplit_port);
+
+    // Read the handshake
+    uint8_t buf[512] = {};
+    conn.read(buf, sizeof(buf));
+
+    // Send the handshake response
+    conn.write(&wbuf[0], wbuf.size());
+
+    // Read MaxScale's response
+    conn.read(buf, sizeof(buf));
+
+    const char response[] = "Bad handshake";
+    test.add_result(memmem(buf, sizeof(buf), response, sizeof(response) - 1) == NULL,
+                    "MaxScale should respond with 'Bad handshake'");
+
+    return test.global_result;
+}