Enum PaddingControlState

enum PaddingControlState {
    UsageDoesNotImplyPadding {
        padding_params: ChannelPaddingInstructionsUpdates,
    },
    PaddingConfigured,
}

State used to control padding

We store this here because:

1. It must be per-channel, because it depends on channel usage. So it can’t be in (for example) ChannelPaddingInstructionsUpdate.

2. It could be in the channel manager’s per-channel state but (for code flow reasons there, really) at the point at which the channel manager concludes for a pending channel that it ought to update the usage, it has relinquished the lock on its own data structure. And there is actually no need for this to be global: a per-channel lock is better than reacquiring the global one.

3. It doesn’t want to be in the channel reactor since that’s super hot.

See also the overview at tor_proto::channel::padding

Variants

UsageDoesNotImplyPadding

No usage of this channel, so far, implies sending or negotiating channel padding.

This means we do not send (have not sent) any ChannelPaddingInstructionsUpdates to the reactor, with the following consequences:

• We don’t enable our own padding.
• We don’t do any work to change the timeout distribution in the padding timer, (which is fine since this timer is not enabled).
• We don’t send any PADDING_NEGOTIATE cells. The peer is supposed to come to the same conclusions as us, based on channel usage: it should also not send padding.

Fields

padding_params: ChannelPaddingInstructionsUpdates

The last padding parameters (from reparameterize)

We keep this so that we can send it if and when this channel starts to be used in a way that implies (possibly) sending padding.

PaddingConfigured

Some usage of this channel implies possibly sending channel padding

The required padding timer, negotiation cell, etc., have been communicated to the reactor via a CtrlMsg::ConfigUpdate.

Once we have set this variant, it remains this way forever for this channel, (the spec speaks of channels “only used for” certain purposes not getting padding).

Trait Implementations

impl Debug for PaddingControlState

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

Formats the value using the given formatter.

impl Default for PaddingControlState

fn default() -> Self

Returns the “default value” for a type.