# IPv6 ## IPv6 Header A IPv6 header consists of a set of fields: ``` 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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 +-------+---------------+---------------------------------------+ |VERSION| Traffic Class | Flow Label | +-------+---------------+-------+---------------+---------------+ | Payload Length | Next Header | Hop-Limit | +-------------------------------+---------------+---------------+ | | | Source Address | | (128 bits) | | | +---------------------------------------------------------------+ | | | Destination Address | | (128 bits) | | | +---------------------------------------------------------------+ ``` * 4-bit protocol version (`IPV6#version`). Attended value is 6 for IPv6, * 8-bit traffic class (\`IPV6#traffic\_class), * 20-bit flow label (`IPv6#flow_label`), * 16-bit payload length (`IPV6#length`), size of IPV6 payload, excluding the header, * 8-bit next header (`IPV6#next`) to indicate upper protocol (6 for TCP, and 17 for UDP by example, but this may also be IPv6 options), * 8-bit hop-limit (`IPV6#hop`), * 128-bit source IPV6 address (`IPV6#src`), * 128-bit destination IPV6 address (`IPV6#dst`), * a body (`IPV6#body`) containing data conveyed by IPv6. A IPV6 header may be built this way: ``` pg> PacketGen::Header::IPv6.new(hop: 32, src: '::1', dst: '::1') => ---- PacketGen::Header::IPv6 ----------------------------------------- Int32 u32: 1610612736 (0x60000000) version: 6 tclass: 0 (0x00) flow_label: 0 (0x00000) Int16 length: 0 (0x0000) Int8 next: 0 (0x00) Int8 hop: 32 (0x20) Addr src: ::1 Addr dst: ::1 ``` ## IPv6 Packet A IPv6 packet may be created this way: ```ruby pkt = PacketGen.gen('IPV6', ttl: 32, src: '10.0.0.1', dst: '20.0.0.1', flag_df: true) pkt.is? 'IPVv' # => true pkt.ipv6 # => PacketGen::Header::IPv6 pkt.ipv6.version # => 6 pkt.ipv6.tclass # => Integer pkt.ipv6.flow_label # => Integer pkt.ipv6.length # => 0 pkt.ipv6.next # => Integer pkt.ipv6.hop # => 32 pkt.ipv6.dst # => '::1' pkt.ipv6.src = '::2' pkt.ipv6.src # => '::2' pkt.body = 'This is a body' pkt.length # => 0 ``` As you can see, `length` is not automatically set to correct value. But it may be set easily with `IPv6#calc_length`. `Packet#calc` may be used too: it automatically call `#calc_sum` and `#calc_length` on all headers responding to them: ``` pg> pkt.calc pg> pkt => -- PacketGen::Packet ------------------------------------------------- ---- PacketGen::Header::IPv6 ----------------------------------------- Int32 u32: 1610612736 (0x60000000) version: 6 tclass: 0 (0x00) flow_label: 0 (0x00000) Int16 length: 14 (0x000e) Int8 next: 0 (0x00) Int8 hop: 32 (0x20) Addr src: ::2 Addr dst: ::1 ---- Body ------------------------------------------------------------ 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 ---------------------------------------------------------------------- 54 68 69 73 20 69 73 20 61 20 62 6f 64 79 This is a body ---------------------------------------------------------------------- ``` ### TCP and UDP headers over IPv6 TCP and UDP headers may be added to a IPv6 packet: ```ruby pg> pkt = PacketGen.gen('IPv6', src: '::1', dst: '::1') pg> pkt.add('TCP', dport: 80, sport: 51234) pg> pkt => -- PacketGen::Packet ------------------------------------------------- ---- PacketGen::Header::IPv6 ----------------------------------------- Int32 u32: 1610612736 (0x60000000) version: 6 tclass: 0 (0x00) flow_label: 0 (0x00000) Int16 length: 0 (0x0000) Int8 next: 6 (0x06) Int8 hop: 64 (0x40) Addr src: ::1 Addr dst: ::1 ---- PacketGen::Header::TCP ------------------------------------------ Int16 sport: 51234 (0xc822) Int16 dport: 80 (0x0050) Int32 seqnum: 6082437 (0x005ccf85) Int32 acknum: 0 (0x00000000) Int16 u16: 20480 (0x5000) data_offset: 5 (0x5) reserved: 0 flags: ......... Int16 window: 0 (0x0000) Int16 checksum: 0 (0x0000) Int16 urg_pointer: 0 (0x0000) Options options: ``` See also . --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://packetgen.gitbook.io/wiki/protocols/ipv6.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.