dhcpkit.ipv6.extensions.prefix_delegation module¶
Implementation of Prefix Delegation options as specified in RFC 3633.
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class
dhcpkit.ipv6.extensions.prefix_delegation.IAPDOption(iaid: bytes = b'x00x00x00x00', t1: int = 0, t2: int = 0, options: Iterable = None)[source]¶ Bases:
dhcpkit.ipv6.options.OptionThe IA_PD option is used to carry a prefix delegation identity association, the parameters associated with the IA_PD and the prefixes associated with it.
The format of the IA_PD option is:
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_IA_PD | option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IAID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | T2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . IA_PD-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- option-code
- OPTION_IA_PD (25).
- option-length
- 12 + length of IA_PD-options field.
- IAID
- The unique identifier for this IA_PD; the IAID must be unique among the identifiers for all of this requesting router’s IA_PDs.
- T1
- The time at which the requesting router should contact the delegating router from which the prefixes in the IA_PD were obtained to extend the lifetimes of the prefixes delegated to the IA_PD; T1 is a time duration relative to the current time expressed in units of seconds.
- T2
- The time at which the requesting router should contact any available delegating router to extend the lifetimes of the prefixes assigned to the IA_PD; T2 is a time duration relative to the current time expressed in units of seconds.
- IA_PD-options
- Options associated with this IA_PD.
The IA_PD-options field encapsulates those options that are specific to this IA_PD. For example, all of the IA_PD Prefix Options carrying the prefixes associated with this IA_PD are in the IA_PD-options field.
An IA_PD option may only appear in the options area of a DHCP message. A DHCP message may contain multiple IA_PD options.
The status of any operations involving this IA_PD is indicated in a Status Code option in the IA_PD-options field.
Note that an IA_PD has no explicit “lifetime” or “lease length” of its own. When the valid lifetimes of all of the prefixes in a IA_PD have expired, the IA_PD can be considered as having expired. T1 and T2 are included to give delegating routers explicit control over when a requesting router should contact the delegating router about a specific IA_PD.
In a message sent by a requesting router to a delegating router, values in the T1 and T2 fields indicate the requesting router’s preference for those parameters. The requesting router sets T1 and T2 to zero if it has no preference for those values. In a message sent by a delegating router to a requesting router, the requesting router MUST use the values in the T1 and T2 fields for the T1 and T2 parameters. The values in the T1 and T2 fields are the number of seconds until T1 and T2.
The delegating router selects the T1 and T2 times to allow the requesting router to extend the lifetimes of any prefixes in the IA_PD before the lifetimes expire, even if the delegating router is unavailable for some short period of time. Recommended values for T1 and T2 are .5 and .8 times the shortest preferred lifetime of the prefixes in the IA_PD that the delegating router is willing to extend, respectively. If the time at which the prefixes in an IA_PD are to be renewed is to be left to the discretion of the requesting router, the delegating router sets T1 and T2 to 0.
If a delegating router receives an IA_PD with T1 greater than T2, and both T1 and T2 are greater than 0, the delegating router ignores the invalid values of T1 and T2 and processes the IA_PD as though the delegating router had set T1 and T2 to 0.
If a requesting router receives an IA_PD with T1 greater than T2, and both T1 and T2 are greater than 0, the client discards the IA_PD option and processes the remainder of the message as though the delegating router had not included the IA_PD option.
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get_option_of_type(*args) → Union[source]¶ Get the first option that is a subclass of the given class.
Parameters: args – The classes to look for Returns: The option or None
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get_options_of_type(*args) → List[source]¶ Get all options that are subclasses of the given class.
Parameters: args – The classes to look for Returns: The list of options
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iaid= None¶ The unique identifier for this IA_PD
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load_from(buffer: bytes, offset: int = 0, length: int = None) → int[source]¶ Load the internal state of this object from the given buffer. The buffer may contain more data after the structured element is parsed. This data is ignored.
Parameters: - buffer – The buffer to read data from
- offset – The offset in the buffer where to start reading
- length – The amount of data we are allowed to read from the buffer
Returns: The number of bytes used from the buffer
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option_type= 25¶
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options= None¶ The list of options contained in this IAPDOption
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save() → Union[source]¶ Save the internal state of this object as a buffer.
Returns: The buffer with the data from this element
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t1= None¶ The time at which the client contacts the server to renew its prefixes
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t2= None¶ The time at which the client contacts any available server to rebind its prefixes
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class
dhcpkit.ipv6.extensions.prefix_delegation.IAPrefixOption(prefix: ipaddress.IPv6Network = None, preferred_lifetime: int = 0, valid_lifetime: int = 0, options: Iterable = None)[source]¶ Bases:
dhcpkit.ipv6.options.OptionThe IA_PD Prefix option is used to specify IPv6 address prefixes associated with an IA_PD. The IA_PD Prefix option must be encapsulated in the IA_PD-options field of an IA_PD option.
The format of the IA_PD Prefix option is:
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_IAPREFIX | option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | preferred-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | valid-lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | prefix-length | | +-+-+-+-+-+-+-+-+ IPv6 prefix | | (16 octets) | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . +-+-+-+-+-+-+-+-+ . . IAprefix-options . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- option-code
- OPTION_IAPREFIX (26).
- option-length
- 25 + length of IAprefix-options field.
- preferred-lifetime
- The recommended preferred lifetime for the IPv6 prefix in the option, expressed in units of seconds. A value of 0xFFFFFFFF represents infinity.
- valid-lifetime
- The valid lifetime for the IPv6 prefix in the option, expressed in units of seconds. A value of 0xFFFFFFFF represents infinity.
- prefix-length
- Length for this prefix in bits.
- IPv6-prefix
- An IPv6 prefix.
- IAprefix-options
- Options associated with this prefix.
In a message sent by a requesting router to a delegating router, the values in the fields can be used to indicate the requesting router’s preference for those values. The requesting router may send a value of zero to indicate no preference. A requesting router may set the IPv6 prefix field to zero and a given value in the prefix-length field to indicate a preference for the size of the prefix to be delegated.
In a message sent by a delegating router the preferred and valid lifetimes should be set to the values of AdvPreferredLifetime and AdvValidLifetime as specified in section 6.2.1, “Router Configuration Variables” of RFC 2461 [4], unless administratively configured.
A requesting router discards any prefixes for which the preferred lifetime is greater than the valid lifetime. A delegating router ignores the lifetimes set by the requesting router if the preferred lifetime is greater than the valid lifetime and ignores the values for T1 and T2 set by the requesting router if those values are greater than the preferred lifetime.
The values in the preferred and valid lifetimes are the number of seconds remaining for each lifetime.
An IA_PD Prefix option may appear only in an IA_PD option. More than one IA_PD Prefix Option can appear in a single IA_PD option.
The status of any operations involving this IA_PD Prefix option is indicated in a Status Code option in the IAprefix-options field.
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load_from(buffer: bytes, offset: int = 0, length: int = None) → int[source]¶ Load the internal state of this object from the given buffer. The buffer may contain more data after the structured element is parsed. This data is ignored.
Parameters: - buffer – The buffer to read data from
- offset – The offset in the buffer where to start reading
- length – The amount of data we are allowed to read from the buffer
Returns: The number of bytes used from the buffer
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option_type= 26¶
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options= None¶ The list of options related to this IAPrefixOption
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preferred_lifetime= None¶ The preferred lifetime of this IPv6 prefix
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prefix= None¶ The IPv6 prefix
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save() → Union[source]¶ Save the internal state of this object as a buffer.
Returns: The buffer with the data from this element
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valid_lifetime= None¶ The valid lifetime of this IPv6 prefix