GTP

The system provides two Python objects alc.gtp1c and alc.gtp2c to inspect and modify the GTPv1 and GTPv2 control packet.

The alc.gtp1c object

Attributes

The object exposes the header fields as attributes on the object.

Attributes defined on alc.gtp1c

Attribute	Field	Access	Type
version	GTP version field	ro	int
ptbit	Protocol Type bit	ro	int
ebit	Flag marking if there is an extension header.	ro	int
sbit	Flag marking if there is a sequence-number field.	ro	int
pnbit	Flag marking if there is an N-PDU field.	ro	int
type	Type of the GTP message	ro	int
len	Length of the GTP message	ro	int
teid	Tunnel Endpoint Identifier	ro	int
seq	Sequence number. None if not present.	ro	int
npdu_number	N-PDU number. None if not present.	ro	int
next_ext_type	Next extension type. None if not present	ro	int
ext_list	List of extension-headers, repesented as a tuple (type, value)	ro	list of (int, bytes) tuples

Methods

alc.Gtp1c.drop()

Drops the packet.

alc.Gtp1c.getIEList()

Returns a list of IE-types that are present in the packet.

• The order of the elements is the same as they appear in the packet.

• If there are multiple instances of the same IE, the IE-type appears multiple times in the tuple.

alc.Gtp1c.get(type, /)

Returns all values of the IEs with the specified type. The values are returned as the exact bytestrings as they appear in the packet.

• If the specified option does not exist, the result is an empty tuple: ()

• If a specific instance has zero length or no values, the corresponding bytestring in the result tuple is an empty bytestring: b””

Parameters

type (int) – IE-type to fetch

Return type

tuple of bytestrings

alc.Gtp1c.set(type, value, /)

Deletes existing IEs of the specified type and inserts new IEs with the specified type and value. Multiple values can be specified in a tuple, in which case an option is added for each item in the tuple.

Parameters

• type (int) – IE-type to set

• value (bytes|tuple(bytes)) – value of the option; length is computed from this value

alc.Gtp1c.clear(type, /)

Removes all IEs with the specified type.

Parameters

type (int) – IE-type to clear

The alc.gtp2c object

Attributes

The object exposes the header fields as attributes on the object.

Attributes defined on alc.gtp2c

Attribute	Field	Access	Type
version	GTP version field	ro	int
pbit	Piggyback flag	ro	int
tbit	Flag marking if there is a TEID present.	ro	int
type	Type of the GTP message	ro	int
len	Length of the GTP message	ro	int
teid	Tunnel Endpoint Identifier. None if not present	ro	int
seq	Sequence number	ro	int

Methods

alc.Gtp2c.drop()

Drops the packet.

alc.Gtp2c.getIEList()

Returns a list of IE-types that are present in the packet.

• The order of the elements is the same as they appear in the packet.

• If there are multiple instances of the same IE, the IE-type appears multiple times in the tuple.

alc.Gtp2c.get(type, instance, /)

Returns all values of the IEs with the specified type. The values are returned as the exact bytestrings as they appear in the packet.

• If the specified option does not exist, the result is an empty tuple: ()

• If a specific instance has zero length or no values, the corresponding bytestring is an empty bytestring: b””

Parameters

• type (int) – IE-type

• instance (int) – IE-instance

Return type

tuple of bytestrings

alc.Gtp2c.set(type, instance, value, /)

Deletes existing IEs with the specified type and instance and inserts new IEs with the specified type, instance, and value. Multiple values can be specified in a tuple, in which case an option is added for each item in the tuple.

Parameters

• type (int) – IE-type

• instance (int) – IE-instance

• value (bytes|tuple(bytes)) – value of the option, length is computed from this value

alc.Gtp2c.clear(type, instance, /)

Removes all IEs with the specified type.

Parameters

• type (int) – IE-type

• instance (int) – IE-instance

alc.Gtp2c.decode_grouped_ie(value)

Decodes the byte-representation of a grouped-IE to a tuple of IEs.

Defined as a static method.

Parameters

value (bytes) – grouped IE value

Returns

returns a tuple where each element represents an IE. Each IE is represented as a tuple (type, instance, value) with types (int, int, bytes).

alc.Gtp2c.encode_grouped_ie(value)

Encodes a tuple of IEs into the byte-representation of a grouped-IE.

Defined as a static method.

Parameters

value (tuple) – tuple of IEs where each IE is represented as a (type, instance, value) tuple.

Returns

byte-representation of the grouped-IE

alc.Gtp2c.get_pco()

Returns the PCO IE (78) as a alc.Pco object.

The returned object can be modified in-place and is reflected in the resulting GTP packet.

Returns

A alc.Pco object

alc.Gtp2c.set_pco(pco)

Accepts a alc.Pco object, encodes it, and uses this as the value for the PCO IE.

Parameters

pco (alc.pco) – alc.Pco object

The alc.Pco class

class alc.Pco(bytes, /)

Creates a new object representing a PCO IE.

Parameters

bytes (bytes) – the bytes representation of the PCO IE.

Attributes

Attributes defined on alc.Pco objects

Attribute	Field	Access	Type
proto	Protocol field	ro	int
length	Length of the embedded protocol	ro	int

Methods

get_container(id, /)

Retrieves the content of all containers with the specified ID.

Parameters

id (int) – ID of the container

Return type

list(bytes)

set_container(id, container, /)

Deletes existing containers of the specified ID and inserts new containers. Multiple containers can be specified in a tuple, in which case a container is added for each entry in the tuple.

Containers of type PAP, CHAP, IPCP, or LCP cannot be modified with this method. See set_pap() and set_chap().

Parameters

• id (int) – ID of the container

• container (bytes or tuple(bytes)) – content of the container

clear_container(id, /)

Removes all containers with the specified ID.

Parameters

id (int) – ID of the container

get_pap()

Returns the PAP container as a alc.Pap object.

set_pap(pap, /)

Replaces the existing PAP container with a new one. Multiple PAP objects can be specified in a tuple.

Parameters

pap (alc.Pap or tuple(alc.Pap)) – PAP object

clear_pap()

Removes all PAP containers.

get_chap()

Returns the CHAP container as a alc.Chap object.

set_chap(chap, /)

Replaces the existing CHAP container with a new one. Multiple CHAP objects can be specified in a tuple.

Parameters

chap (alc.Chap or tuple(alc.Chap)) – CHAP object

clear_chap()

Removes all CHAP containers.

Breaking changes

Renamed methods

Warning

The following methods of alc.Gtp2c class have been renamed in Python 3 API:

• Python 2 str_to_groupedIE is now Python 3 alc.Gtp2c.decode_grouped_ie()

• Python 2 groupedIE_to_str is now Python 3 alc.Gtp2c.encode_grouped_ie()