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// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
package packet
import (
"io"
"net/netip"
"time"
)
// Callback describes a function which is called to
// record packets when debugging packet-capture.
// Such callbacks must not take ownership of the
// provided data slice: it may only copy out of it
// within the lifetime of the function.
type CaptureCallback func(CapturePath, time.Time, []byte, CaptureMeta)
// CaptureSink is the minimal interface from [tailscale.com/feature/capture]'s
// Sink type that is needed by the core (magicsock/LocalBackend/wgengine/etc).
// This lets the relativel heavy feature/capture package be optionally linked.
type CaptureSink interface {
// Close closes
Close() error
// NumOutputs returns the number of outputs registered with the sink.
NumOutputs() int
// CaptureCallback returns a callback which can be used to
// write packets to the sink.
CaptureCallback() CaptureCallback
// WaitCh returns a channel which blocks until
// the sink is closed.
WaitCh() <-chan struct{}
// RegisterOutput connects an output to this sink, which
// will be written to with a pcap stream as packets are logged.
// A function is returned which unregisters the output when
// called.
//
// If w implements io.Closer, it will be closed upon error
// or when the sink is closed. If w implements http.Flusher,
// it will be flushed periodically.
RegisterOutput(w io.Writer) (unregister func())
}
// CaptureMeta contains metadata that is used when debugging.
type CaptureMeta struct {
DidSNAT bool // SNAT was performed & the address was updated.
OriginalSrc netip.AddrPort // The source address before SNAT was performed.
DidDNAT bool // DNAT was performed & the address was updated.
OriginalDst netip.AddrPort // The destination address before DNAT was performed.
}
// CapturePath describes where in the data path the packet was captured.
type CapturePath uint8
// CapturePath values
const (
// FromLocal indicates the packet was logged as it traversed the FromLocal path:
// i.e.: A packet from the local system into the TUN.
FromLocal CapturePath = 0
// FromPeer indicates the packet was logged upon reception from a remote peer.
FromPeer CapturePath = 1
// SynthesizedToLocal indicates the packet was generated from within tailscaled,
// and is being routed to the local machine's network stack.
SynthesizedToLocal CapturePath = 2
// SynthesizedToPeer indicates the packet was generated from within tailscaled,
// and is being routed to a remote Wireguard peer.
SynthesizedToPeer CapturePath = 3
// PathDisco indicates the packet is information about a disco frame.
PathDisco CapturePath = 254
)
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