Module capture 

Available on crate features quic and std only.

Reading a first flight back from the wire: what any observer sees, and what one that can open the Initial packets sees.

The pipeline here needs no cryptography of its own: it splits datagrams, and — given a KeyProvider — removes Initial protection, reassembles the ClientHello and reads the transport parameters. Initial keys derive from the destination connection ID and version salt (RFC 9001 §5.2), so both a passive observer and the destination server can supply them; the keys themselves come from the engine’s TLS backend behind that seam.

Most callers hand a client’s first datagrams (the ones sent before it hears from the server) and a KeyProvider to first_flight, which runs the whole pipeline and returns a FirstFlight summary to fingerprint or turn into a crate::profile::QuicProfile. The steps are also public for finer control: observe splits one datagram with no keys; ObservedDatagram::unprotect_initials opens that datagram’s Initial packets into InitialPackets; client_hello takes those InitialPackets from across the whole flight and reassembles the ClientHello from their CRYPTO frames; transport_parameters reads it, and version_information pulls the negotiated/available versions out of those. So the packets client_hello wants are simply the InitialPackets unprotect_initials returned.

Structs

FirstFlight

What a client’s first flight looks like, as the profile tests compare it.

InitialKeys

The Initial keys that open one direction of a captured flight.

InitialPacket

An Initial packet after its protection is removed.

ObservedDatagram

A datagram split into its packets.

ObservedPacket

One packet of a datagram as an observer without keys sees it.

RawParameter

A transport parameter as it was sent: identifier and raw value, in wire order.

Enums

CaptureError

Why a datagram or packet could not be read.

ObservedFrame

A frame as an observer with Initial keys sees it; consecutive PADDING bytes are one run.

PacketKind

What kind of packet a header announces (RFC 8999 §5, RFC 9000 §17).

Traits

KeyProvider

Supplies the Initial keys needed to open a captured first flight.

Functions

client_hello

The ClientHello reassembled from Initial packets, when the CRYPTO data covers it from offset zero through its length.

first_flight

Read a client’s first flight: the datagrams it sent before hearing from the server.

observe

Split a datagram into packets using only the invariant layout (RFC 8999 §5) and each version’s type bits and Length fields. A short header takes the rest of the datagram; bytes after a packet that cannot start another one are reported as trailing.

transport_parameters

The transport parameters of a ClientHello handshake message, in the order they were sent.

version_information

The version_information parameter among parameters, decoded as a client’s.