Struct RelayCell 

pub struct RelayCell {
    pub circ_id: u32,
    pub command: RelayCommand,
    pub command_int: u8,
    pub recognized: u16,
    pub stream_id: u16,
    pub digest: u32,
    pub data: Vec<u8>,
    pub unused: Vec<u8>,
}

End-to-end encrypted relay cell.

RELAY cells carry encrypted data through circuits. Each relay cell is encrypted/decrypted at each hop using the circuit’s encryption keys.

Wire Format

[ CircID ][ 3 (RELAY) ][ Command (1) ][ Recognized (2) ][ StreamID (2) ]
[ Digest (4) ][ Length (2) ][ Data ][ Padding ]

Fields

• command - Relay sub-command (DATA, BEGIN, END, etc.)
• recognized - Zero if cell is for us (used for decryption check)
• stream_id - Stream identifier within the circuit
• digest - Running digest for integrity verification
• data - Payload data

Stream ID Rules

Some commands require a stream ID, others forbid it:

• Required: BEGIN, DATA, END, CONNECTED, RESOLVE, RESOLVED, BEGIN_DIR
• Forbidden: EXTEND, EXTENDED, TRUNCATE, TRUNCATED, DROP, EXTEND2, EXTENDED2

Fields

circ_id: u32

Circuit ID this cell belongs to.

command: RelayCommand

Relay sub-command.

command_int: u8

Integer value of the command.

recognized: u16

Recognition field (0 if cell is for us).

stream_id: u16

Stream identifier within the circuit.

digest: u32

Running digest for integrity.

data: Vec<u8>

Payload data.

unused: Vec<u8>

Unused padding bytes.

Implementations

impl RelayCell

pub fn new( circ_id: u32, command: RelayCommand, data: Vec<u8>, digest: u32, stream_id: u16, ) -> Result<Self, Error>

Creates a new RELAY cell.

Arguments

• circ_id - Circuit ID
• command - Relay sub-command
• data - Payload data
• digest - Running digest (0 for unencrypted cells)
• stream_id - Stream identifier

Errors

Returns Error::Protocol if:

• stream_id is 0 but command requires a stream ID
• stream_id is non-zero but command forbids stream IDs

pub fn pack(&self, link_protocol: &LinkProtocol) -> Vec<u8>

Packs this cell into bytes for transmission.

pub fn unpack(payload: &[u8], circ_id: u32) -> Result<Self, Error>

Unpacks a RELAY cell from payload bytes.

Errors

Returns Error::Protocol if payload is malformed.

Trait Implementations

impl Clone for RelayCell

fn clone(&self) -> RelayCell

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RelayCell

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for RelayCell

fn eq(&self, other: &RelayCell) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for RelayCell