Handle broken TLS conf better

Co-authored-by: Jean-Baptiste Doumenjou <925513+jbdoumenjou@users.noreply.github.com>
Co-authored-by: Romain <rtribotte@users.noreply.github.com>

integration/https_test.go

@@ -1226,3 +1226,53 @@ func (s *HTTPSSuite) TestWithDomainFronting(c *check.C) {
 		c.Assert(err, checker.IsNil)
 	}
 }
+
+// TestWithInvalidTLSOption verifies the behavior when using an invalid tlsOption configuration.
+func (s *HTTPSSuite) TestWithInvalidTLSOption(c *check.C) {
+	backend := startTestServer("9010", http.StatusOK, "server1")
+	defer backend.Close()
+
+	file := s.adaptFile(c, "fixtures/https/https_invalid_tls_options.toml", struct{}{})
+	defer os.Remove(file)
+	cmd, display := s.traefikCmd(withConfigFile(file))
+	defer display(c)
+	err := cmd.Start()
+	c.Assert(err, checker.IsNil)
+	defer s.killCmd(cmd)
+
+	// wait for Traefik
+	err = try.GetRequest("http://127.0.0.1:8080/api/rawdata", 500*time.Millisecond, try.BodyContains("Host(`snitest.com`)"))
+	c.Assert(err, checker.IsNil)
+
+	testCases := []struct {
+		desc       string
+		serverName string
+	}{
+		{
+			desc:       "With invalid TLS Options specified",
+			serverName: "snitest.com",
+		},
+		{
+			desc:       "With invalid Default TLS Options",
+			serverName: "snitest.org",
+		},
+		{
+			desc: "With TLS Options without servername (fallback to default)",
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+
+		tlsConfig := &tls.Config{
+			InsecureSkipVerify: true,
+		}
+		if test.serverName != "" {
+			tlsConfig.ServerName = test.serverName
+		}
+
+		conn, err := tls.Dial("tcp", "127.0.0.1:4443", tlsConfig)
+		c.Assert(err, checker.NotNil, check.Commentf("connected to server successfully"))
+		c.Assert(conn, checker.IsNil)
+	}
+}