TCP¶
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class
os_ken.lib.packet.tcp.
tcp
(src_port=1, dst_port=1, seq=0, ack=0, offset=0, bits=0, window_size=0, csum=0, urgent=0, option=None)¶ TCP (RFC 793) header encoder/decoder class.
An instance has the following attributes at least. Most of them are same to the on-wire counterparts but in host byte order. __init__ takes the corresponding args in this order.
Attribute
Description
src_port
Source Port
dst_port
Destination Port
seq
Sequence Number
ack
Acknowledgement Number
offset
Data Offset (0 means automatically-calculate when encoding)
bits
Control Bits
window_size
Window
csum
Checksum (0 means automatically-calculate when encoding)
urgent
Urgent Pointer
option
List of
TCPOption
sub-classes or an bytearray containing options. None if no options.-
has_flags
(*flags)¶ Check if flags are set on this packet.
returns boolean if all passed flags is set
Example:
>>> pkt = tcp.tcp(bits=(tcp.TCP_SYN | tcp.TCP_ACK)) >>> pkt.has_flags(tcp.TCP_SYN, tcp.TCP_ACK) True
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classmethod
parser
(buf)¶ Decode a protocol header.
This method is used only when decoding a packet.
Decode a protocol header at offset 0 in bytearray buf. Returns the following three objects.
An object to describe the decoded header.
A packet_base.PacketBase subclass appropriate for the rest of the packet. None when the rest of the packet should be considered as raw payload.
The rest of packet.
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serialize
(payload, prev)¶ Encode a protocol header.
This method is used only when encoding a packet.
Encode a protocol header. Returns a bytearray which contains the header.
payload is the rest of the packet which will immediately follow this header.
prev is a packet_base.PacketBase subclass for the outer protocol header. prev is None if the current header is the outer-most. For example, prev is ipv4 or ipv6 for tcp.serialize.
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