TTCN-3 and Eclipse TITAN for testing protocol stacks
====================================================
:author:	Harald Welte <laforge@gnumonks.org>
:copyright:	2017-2018 by Harald Welte (License: CC-BY-SA)
:backend:	slidy
:max-width:	45em

== Protocol Testing

Important for:

* conformance to specification
* ensuring interoperability
* network security
* regression testing
* performance

== Protocol Testing

No standard methodology, language, approach, tool

* testing implementation against itself
** works only for symmetric protocols
** wouldn't cover lots of problems
* testing against wireshark
** wireshark often way more tolerant than spec
* custom implementation
** in Python (e.g. using scapy)
** in Erlang (good binary encoder/decoder) or other languages
* specific tools like packetdrill

== Protocol Testing

Personal story: During past years,

* I implemented tons of [telecom] protocols / stacks at Osmocom.org
* I was looking for better tools to help [automatic] testing
** primarily functional testing (correctness / conformance)
** not so much performance testing
* I figured Ideal test tool would...
** allow very productive and expressive way to describe encoding/decoding
** allow very convenient pattern matching on incoming messages
** allow exchange of messages asynchronously with implementation under test
* I stumbled on TTCN-3 occasionally and investigated

== The TTCN-3 Language

* domain-specific language *just* for protocol conformance tests
* TTCN history back to 1983 (!), TTCN-3 since 2000
* used extensively in classic telecom sector (Ericsson, Nokia, etc.)
* ETSI developed and published abstract test suites in TTCN-3 for
** IPv6, SIP, DIAMETER, ePassports, Digital Mobiel Radio, 6LoWPAN
* Other bodies published test suites for
** CoAP, MQTT, MOST, AUTOSAR

But: Until 2015, only proprietary tools / compilers :(

== Eclipse TITAN

* After TTCN-3 specification in 2000, Ericsson internally develops TTCN-3 toolchain
* adopted for many Ericsson-internal testing of all kinds of products
* proprietary software with commercial licenses
* 300,000 lines of Java + 1.6 Million lines of C++
* Released as Open Source as "Eclipse TITAN" in 2015
** Not just TTCN-3 compiler, but also extensive documentations and many protocol modules, test ports as well as Eclipse IDE, Log file viewer/visualizer, etc.
* `eclipse-titan` part of standard Debian / Ubuntu archive, only one apt-get away

Great, we can finally use TTCN-3 in FOSS!

== Eclipse TITAN compiler workflow

[graphviz]
----
digraph G {
  progra [label="Human Developer"];
  ttcn3 [label="TTCN-3 source (ATS)"];
  cpp [label="Generated C++ source"];
  exec [label="Binary Executable (ETS)"];
  tps [label="Other C++ sources, as needed"];
  progra -> ttcn3 [label="writes code"];
  ttcn3 -> cpp [label="ttcn3_compiler"];
  cpp -> exec [label="GNU gcc / g++"];
  tps -> cpp
}
----

* TITAN actually _compiles_ into executable binaries, it is not using a VM or scripting
** ATS: Abstract Test Suite (source code)
** ETS: Executable Test Suite (executable code)

== TTCN-3 Language Features (with TITAN)

* comprehensive type system
* parametric templates
* variety of encoders/decoders
* automatic / comprehensive logging framework
* powerful program control statements
* built-in notion of tests cases, test suites, verdicts, ...
* runtime / executor for parallel test components + aggregating results

== TTCN-3 Basic Types

* Simple basic types such as `integer`, `float`, `boolen`
* Basic string types such as `bitstring`, `octetstring`, `hexstring`, `charstring` (IA5) and `universal charstring` (UCS-4).
* Structured Types `record`, `set`, `record of`, `set of`
* Verdict type `verdicttype`
** can have either value `none`, `pass`, `inconc`, `fail`,  or `error`
** verdict can only _deteriorate_ (`pass` -> `fail`) but never improve (`error` -> `pass`)
** every test case implicitly has a verdict, no need to explicitly declare a variable of `verdicttype`

== TTCN-3 Structured Types

A structured type is an abstract type comprised of other types, whcih can be nested.
An example for a `record` type (similar to a C-language `struct`) is shown below

--------
type record MyMessageType {
  integer field1 optional<1>,
  charstring field2,
  boolean field3
};
--------
<1> optional members may be present or not

== TTCN-3 Union Type

A union expresses a set of alternative types of which one alternative must be chosen.

--------
type union MyMessageUnion {
  integer field1,
  charstring field2,
};
--------

Difference to C-language union: `ischosen()` can be used to learn which of the union members is
chosen/defined!


== Not-used and omit

* until a variable or field of structured type is assigned, it is _unbound_
* whenever a _value_ is expected, TTCN-3 runtime will create an error for _unbound_
* in case of absence of optional fields, explicit `omit` value must be assigned!

== Sub-typing

Sub-typing can be used to further constrain a given type.  Typical examples include constrained number ranges,
and string patterns

--------
type integer MyIntRange (1..100);
type integer MyIntRange8 (0..infinity);
type charstring MyCharRange (”k”..”w");
type charstring SideType (”left”, ”right”);
type integer MyIntListRange (1..5,7,9);
type record length(0..10) of integer RecOfInt;
type charstring CrLfTermStrin (pattern ”*\r\n”);
--------

== Templates

* Matching incoming messages against some kind of specification is one of the most common tasks in testing protocols
** some expected fields are static (message type)
** some expected fields are known (source address)
** some fields are chosen by sender (some identifier)
** some fields we don't care (optional headers that may or may not be present)
* TTCN-3 Templates provide elegant solution for this, avoiding any explicit code to be written
** templates can even be parametric, i.e. they can be instantiated with "arguments"
* templates can also be used for sending messages, if they are fully specified/qualified

== Templates

--------
// Value list template
template charstring tr_SingleABorC := (”A”, ”B”, ”C”);
--------

--------
// Value range
template float tr_NearPi := (3.14 .. 3.15);
template integer tr_FitsToOneByte := (0 .. 255);
template integer tr_GreaterThanZero := (1 .. infinity);
--------

--------
// Intermixed value list and range matching
template integer tr_Intermixed := ((0..127), 200, 255);
--------

== Matching inside values

--------
// Using any element matching inside a bitstring value
// Last 2 bits can be '0' or '1'
template bitstring tr_AnyBSValue := ’101101??’B;
--------

--------
// Matches charstrings with the first character "a"
// and the last one "z"
template charstring tr_0 := pattern "a*z";
--------

* more capabilities using `complement`, `ifpresent`, `subset`, `superset`, `permutation` constructs not
  covered here


== Parametric Templates

See below for an example of a parametric template:

--------
type record MyMessageType {
  integer field1 optional,
  charstring field2,
  boolean field3
};

template MyMessageType trMyTemplte(boolean pl_param) := {
  field1 : = ?, // present, but any value
  field2 : = (”B”, ”O”, ”Q”) ,
  field3 := pl_param
};
--------

The built-in `match()` function can be used to check if a given value matches a given template.  Some TTCN-3
statements such as `receive()` have built-in capabilities for template matching, avoiding even the explicit
call of `match()` in many cases.

== Template Hierarchy

Using modified templates, one can build a hierarchy of templates: From the specific to the unspecific

----
template MyMsgType t_MyMsgAny := {
  msg_type := ?,
  foo := bar
};

template MyMsgType t_MyMsg23 modifies t_MyMsgAny := {
  msg_type := 23,
};
----
where

* _t_MyMsgAny_ matches a message with any message type and "foo=bar", while
* _t_MMyMsg23_ matches only those that have "foo=bar" and "msg_type=23"

== Encoders/Decoders

* type system, templates, matching are all nice and great, but we need to get data from wire format into
  TTCN-3 abstract types
* TTTCN-3 specifies importing of formal schema definitios, such as ASN.1, IDL, XSD (XML) and JSON
* TITAN has additional codecs for those (many) protocols that lack formal syntax
** `raw` codec for binary protocols (e.g. GTP)
** `text` codec for text based protocols (e.g. HTTP, MGCP, IMAP, ...)
* codecs allow you to _express/describe_ the format (declarative programming) rather than the usual imperative approach

== TITAN raw codec: UDP Example

How to express an UDP header using TITAN raw codec

--------
type integer LIN2_BO_LAST (0..65535) with {
  variant ”FIELDLENGTH(16), COMP(nosign), BYTEORDER(last)”
};
type record UDP_header {
  LIN2_BO_LAST srcport,
  LIN2_BO_LAST dstport,
  LIN2_BO_LAST len,
  LIN2_BO_LAST cksum
} with { variant ”FIELDORDER(msb)” };
type record UDP packet {
  UDP_header header
  octetstring payload
} with {
  variant (header) ”LENGTHTO(header, payload), LENGTHINDEX(len)”
};
--------

== TITAN raw codec: GTP Example

How to express an GTP header using TITAN raw codec

--------
type record GRE_Header {
  BIT1 csum_present,
  BIT1 rt_present,
  BIT1 key_present,
  ...
  OCT2 protocol_type,
  OCT2 checksum optional,
  OCT2 offset optional,
  OCT4 key otional,
  ...
} with {
  variant (checksum) "PRESENCE(csum_present='1', rt_present='1'B)"
  variant (offset) "PRESENCE(csum_present='1'B, rt_present='1'B)"
  variant (key) "PRESENCE(key_present='1'B)"
}
--------


== TITAN text codec: MGCP Example

--------
type charstring MgcpVerb ("EPCF", "CRCX", "MDCX", "DLCX", "RQNT", "NTFY",
                          "AUEP", "AUCX", "RSIP") with {
  variant "TEXT_CODING(,convert=upper_case,,case_insensitive)"
};
type charstring MgcpTransId     (pattern "\d#(1,9)");
type charstring MgcpEndpoint    (pattern "*@*");
type charstring MgcpVersion     (pattern "\d.\d") with {
  variant "BEGIN('MGCP ')"
};
type record MgcpCommandLine {
        MgcpVerb        verb,
        MgcpTransId     trans_id,
        MgcpEndpoint    ep,
        MgcpVersion     ver
} with {
        variant "SEPARATOR(' ', '[\t ]+')"
        variant "END('\r\n', '([\r\n])|(\r\n)')"
};
--------

== Program Control Statements

* `if` / `else` like in C
* `select` statement similar to C `switch`
* `for`, `while`, `do-while` loops like in C
* `goto` and `label`
* `break` and `continue` like in C

== Abstract Communications Operations

* TTCN-3 test suites communicate with _implementation under test_ through abstract TestPorts
** TestPorts can be implemented in TTCN-3 or C++ and linked in
** TestPorts must be _connected_ before using send/receive operaitons
** TITAN provides TestPorts for e.g. packet socket, IP/UDP/TCP/SCTP socket, ...
* `<port>.send(<ValueRef>)` performs non-blocking send
** Literal value, constant, variable, specific value template, ...
* `<port>.receive(<TemplateRef>)` or `<port>.receive` performs blocking receive
** literal value, constant, variable, template (with matching!), inline template

'... but if receive blocks, how can we wait for any of N events?

== Program Control and Behavior

* program statements are executed in order
* blocking statements block the execution of the component
* occurrence of unexpected event may cause infinite blocking

----
// x must be the first on queue P, y the second
P.receive(x); // Blocks until x appears on top of queue P
P.receive(y); // Blocks until y appears on top of queue P
// When y arrives first then P.receive(x) blocks -> error
----

This is what leads to the `alt` statement:
`alt` declares a seto alternatives covering all events, which

* can happen: expected messages, timeouts, ...
* must not happen: unexpected faulty messages, no message received, ...
* all alternatives inside `alt` are blocking operations

== The `alt` statement

----
P.send(req)
T.start;
// ...
alt {
[] P.receive(resp)  { /* actions to do and exit alt */ }
[] any port.receive { /* handle unexpected event */ }
[] T.timeout        { /* handle timer expiry and exit */ }
}
----

* [] is guard condition enables or disables the alternative
** usually empty `[]` equals `[true]`
** can contain a condition like `[x > 0]`
** very good for e.g. state machines to activate some alternatives only in certain states while others may
occur in any state


== The `alt` and `repeat` statements

The `repeat` statement

* takes a new snapshot and re-evaluates the alt statement
* can appear as last statement in statement blocks of statements

----
P.send(req)
T.start;
alt {
  [] P.receive(resp)       { /* actions to do and exit alt */ }
  [] P.receive(keep_alive) { /* handle keep alive message */
                             repeat }
  [] any port.receive      { /* handle unexpected event */ }
  [] T.timeout             { /* handle timer expiry and exit */ }
}
----

== The `interleave` statement

The `interleave` statement

* enforces N matching events happen exactly once
* permits any order!

----
interleave {
  [] P.receive(1) { /* actions, optional */ }
  [] Q.receive(4) { /* actions, optional */ }
  [] R.receive(6) { /* actions, optional */ }
}
----

== The `altstep` construct

* collection of set of common/shared `alt` 
** such as responding to a keep-alive PING, depending on protocol
* invoked in-line, inside `alt` statements or _activated as default_

Definition of an `altstep` for PING/PONG handling and guard timer:

----
altstep my_altstep() {
  [] P.receive(tr_PING) { P.send(ts_PONG); }
  [] T_guard.timeout { setverdict(fail, "Guard timer timed out"); }
}
----

== The `altstep` construct

Explicit Usage of the `my_altstep` defined on previous slide:

----
P.send(foo)
alt {
  [] P.receive(bar)
  [] my_altstep()
}
----

this dynamically adds the alternatives from `my_altstep` at the given location
and priority of the above `alt`, ensuring that one doesn't have to repeat
ping/pong handling as well as global guard timer timeout handling in every `alt`
or every single test case all over again.


== default `altstep` activation

* in previous slide, `altstep` invocation was explicit
* some behavior is so universal, that you want to activate it _always_

----
altstep as_pingpong() {
  [] P.receive(tr_PING) { P.send(ts_PONG); }
}
...
var default d1 := activate(as_pingpong());
... /* code executing with as_pingpong activated */
deactivate(d1);
----

* all alt-statements implicitly have as_pingpong active
* but also all _stand-alone receive statements_ !

== TTCN-3 modules

TTCN-3 code is written in _modules_

* a test suite consists of one or more modules
* a module contains _module definitions_ and an optional _control part_
** _parameters_ (automatically configurable via config file)
** definition of _data types_, _constants_, _templates_
** definition of _communications ports_
** definition of _test components_, _functions_ _altsteps_ and _test cases_
** _control part_ determines default order/execution of test cases
* modules can import from each other (think in python terms)

== Examples

Let's have a look at some real-world examples and do a bit of a walk-through
before continuing with the slides...

== Logging

* TITAN runtime contains extensive logging framework
* config file determines log level for various different subsystems
** e.g. any encode, decode, receive, transmit operations logged
** timer starts, expirations
** any changes to test case verdict
* explicit logging from code by use of `log()` built-in function
* `ttcn3_logformat` tool for pretty-printing log files
* `ttcn3_logmerge` tool for merging/splicing multiple logs
* log plugins e.g. for generating JUnit-XML available
** facilitates easy reporting / integration to Jenkins or other CI

== Logging

Log file format example:

----
// abstract data type before encode
13:30:41.243536 Sent on GTPC to system @GTP_CodecPort.Gtp1cUnitdata : { peer := { connId := 1, remName := "127.0.23.1", remPort := 2123 }, gtpc := { pn_bit := '0'B, s_bit := '1'B, e_bit := '0'B, spare := '0'B, pt := '1'B, version := '001'B, messageType := '01'O, lengthf := 0, teid := '00000000'O, opt_part := { sequenceNumber := '3AAC'O, npduNumber := '00'O, nextExtHeader := '00'O, gTPC_extensionHeader_List := omit }, gtpc_pdu := { echoRequest := { private_extension_gtpc := omit } } } }

// 'msg' contains encoded binary data actually sent via socket
13:30:41.243799 Outgoing message was mapped to @IPL4asp_Types.ASP_SendTo : { connId := 1, remName := "127.0.23.1", remPort := 2123, proto := { udp := { } }, msg := '32010004000000003AAC0000'O }
----

== Logging

The same log file lines if run through `ttcn3_logformat`

----
13:30:41.243536 Sent on GTPC to system @GTP_CodecPort.Gtp1cUnitdata : {
    peer := {
        connId := 1,
        remName := "127.0.23.1",
        remPort := 2123
    },
    gtpc := {
        pn_bit := '0'B,
        s_bit := '1'B,
        e_bit := '0'B,
        spare := '0'B,
        pt := '1'B,
        version := '001'B,
        messageType := '01'O,
        lengthf := 0,
        teid := '00000000'O,
        opt_part := {
            sequenceNumber := '3AAC'O,
            npduNumber := '00'O,
            nextExtHeader := '00'O,
            gTPC_extensionHeader_List := omit
        },
        gtpc_pdu := {
            echoRequest := {
                private_extension_gtpc := omit
            }
        }
    }
}
13:30:41.243799 Outgoing message was mapped to @IPL4asp_Types.ASP_SendTo : {
    connId := 1,
    remName := "127.0.23.1",
    remPort := 2123,
    proto := {
        udp := { }
    },
    msg := '32010004000000003AAC0000'O
}
----


== Existing TITAN Source

* Protocol encoding/decoding
** BSSAP+, BSSGP, BSSMAP, CoAP, DSS1, DUA, EAP, GRE, GTP, HTTP, ISUP, LLC, M2PA, M2UA, MQTT, MongoDB, NDP, NS,
   NTAF, ROSE, SCTP, SDP, SNDCP, STOMP, STUN, SUA, TLS, WTP, DNS, IP, SMPP, SNMP, IKEv2, DHCP, PPP, RTP, TCP,
   UDP, XMPP, DHCPv6, SMTP, ICMP, RTSP, ICMPv6, DIAMETER, FrameRelay, ProtoBuff, IUA, L2TP, M3UA, MIME,
   WebSocket, H.248, IMAP, IPsec, SRTP, MSRP, ICAP, RADIUS
* Protocol Emulation
** M3UA, SCCP, SUA
* Test Ports
** GPIO, MTP3, Serial, SocketCAN, SCTP, SIP, HTTP, Telnet, UDP, pcap file, pipe, SQL, TCP, SUNRPC, SSH, STDINOUT, sockets, LDAP


== Further Reading

* Ericsson TTCN-3 tutorial http://www.ttcn-3.org/files/TTCN3_P.pdf
* An Introduction to TTCN-3, 2nd Edition <http://www.wiley.com/go/willcock_TTCN-3_2e>
* Modules https://github.com/eclipse
* More Modules http://git.eclipse.org/
* Debian https://packages.debian.org/search?keywords=eclipse-titan
* Ubuntu https://packages.ubuntu.com/search?keywords=eclipse-titan

== EOF

End of File
