Documentation
¶
Overview ¶
Package tcp contains the implementation of the TCP transport protocol. To use it in the networking stack, this package must be added to the project, and activated on the stack by passing tcp.ProtocolName (or "tcp") as one of the transport protocols when calling stack.New(). Then endpoints can be created by passing tcp.ProtocolNumber as the transport protocol number when calling Stack.NewEndpoint().
Index ¶
- Constants
- Variables
- func FindWndScale(wnd seqnum.Size) int
- func TrimSACKBlockList(sack *SACKInfo, rcvNxt seqnum.Value)
- func UpdateSACKBlocks(sack *SACKInfo, segStart seqnum.Value, segEnd seqnum.Value, ...)
- type ErrSaveRejection
- type Forwarder
- type ForwarderRequest
- type ReceiveBufferSizeOption
- type SACKEnabled
- type SACKInfo
- type SendBufferSizeOption
Constants ¶
const ( // ProtocolName is the string representation of the tcp protocol name. ProtocolName = "tcp" // ProtocolNumber is the tcp protocol number. ProtocolNumber = header.TCPProtocolNumber // DefaultBufferSize is the default size of the receive and send buffers. DefaultBufferSize = 1 << 20 // 1MB )
const (
// InitialCwnd is the initial congestion window.
InitialCwnd = 10
)
const ( // MaxSACKBlocks is the maximum number of SACK blocks stored // at receiver side. MaxSACKBlocks = 6 )
Variables ¶
var ( // SynRcvdCountThreshold is the global maximum number of connections // that are allowed to be in SYN-RCVD state before TCP starts using SYN // cookies to accept connections. // // It is an exported variable only for testing, and should not otherwise // be used by importers of this package. SynRcvdCountThreshold uint64 = 1000 )
Functions ¶
func FindWndScale ¶
FindWndScale determines the window scale to use for the given maximum window size.
func TrimSACKBlockList ¶
TrimSACKBlockList updates the sack block list by removing/modifying any block where start is < rcvNxt.
func UpdateSACKBlocks ¶
func UpdateSACKBlocks(sack *SACKInfo, segStart seqnum.Value, segEnd seqnum.Value, rcvNxt seqnum.Value)
UpdateSACKBlocks updates the list of SACK blocks to include the segment specified by segStart->segEnd. If the segment happens to be an out of order delivery then the first block in the sack.blocks always includes the segment identified by segStart->segEnd.
Types ¶
type ErrSaveRejection ¶
type ErrSaveRejection struct {
Err error
}
ErrSaveRejection indicates a failed save due to unsupported tcp endpoint state.
func (ErrSaveRejection) Error ¶
func (e ErrSaveRejection) Error() string
Error returns a sensible description of the save rejection error.
type Forwarder ¶
type Forwarder struct {
// contains filtered or unexported fields
}
Forwarder is a connection request forwarder, which allows clients to decide what to do with a connection request, for example: ignore it, send a RST, or attempt to complete the 3-way handshake.
The canonical way of using it is to pass the Forwarder.HandlePacket function to stack.SetTransportProtocolHandler.
func NewForwarder ¶
func NewForwarder(s *stack.Stack, rcvWnd, maxInFlight int, handler func(*ForwarderRequest)) *Forwarder
NewForwarder allocates and initializes a new forwarder with the given maximum number of in-flight connection attempts. Once the maximum is reached new incoming connection requests will be ignored.
If rcvWnd is set to zero, the default buffer size is used instead.
func (*Forwarder) HandlePacket ¶
func (f *Forwarder) HandlePacket(r *stack.Route, id stack.TransportEndpointID, vv *buffer.VectorisedView) bool
HandlePacket handles a packet if it is of interest to the forwarder (i.e., if it's a SYN packet), returning true if it's the case. Otherwise the packet is not handled and false is returned.
This function is expected to be passed as an argument to the stack.SetTransportProtocolHandler function.
type ForwarderRequest ¶
type ForwarderRequest struct {
// contains filtered or unexported fields
}
ForwarderRequest represents a connection request received by the forwarder and passed to the client. Clients must eventually call Complete() on it, and may optionally create an endpoint to represent it via CreateEndpoint.
func (*ForwarderRequest) Complete ¶
func (r *ForwarderRequest) Complete(sendReset bool)
Complete completes the request, and optionally sends a RST segment back to the sender.
func (*ForwarderRequest) CreateEndpoint ¶
CreateEndpoint creates a TCP endpoint for the connection request, performing the 3-way handshake in the process.
func (*ForwarderRequest) ID ¶
func (r *ForwarderRequest) ID() stack.TransportEndpointID
ID returns the 4-tuple (src address, src port, dst address, dst port) that represents the connection request.
type ReceiveBufferSizeOption ¶
ReceiveBufferSizeOption allows the default, min and max receive buffer size for TCP endpoints to be queried or configured.
type SACKEnabled ¶
type SACKEnabled bool
SACKEnabled option can be used to enable SACK support in the TCP protocol. See: https://tools.ietf.org/html/rfc2018.
type SACKInfo ¶
type SACKInfo struct {
// Blocks is the maximum number of SACK blocks we track
// per endpoint.
Blocks [MaxSACKBlocks]header.SACKBlock
// NumBlocks is the number of valid SACK blocks stored in the
// blocks array above.
NumBlocks int
}
SACKInfo holds TCP SACK related information for a given endpoint.
type SendBufferSizeOption ¶
SendBufferSizeOption allows the default, min and max send buffer sizes for TCP endpoints to be queried or configured.
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