zakura-network 5.0.1

Networking code for the Zakura node. Internal crate, published to support cargo install zakura
Documentation 
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//! Helpers for durable header-root authentication frontiers.

use super::events::HeaderRootAuthState;
use super::state::{RangePriority, RangeRequest};
use super::HeaderRangePayload;
use zakura_chain::block;

/// Build an authentication request from an exact next-frontier retained payload.
///
/// The complete single-peer payload is kept intact so its terminal header remains
/// the successor witness for the confirmed prefix.
pub(super) fn retained_root_auth_range(
    auth: HeaderRootAuthState,
    payload: &HeaderRangePayload,
    handoff: block::Height,
) -> Option<RangeRequest> {
    let expected_start = auth
        .authenticated_height
        .0
        .checked_add(1)
        .map(block::Height)?;
    (payload.range().start() == expected_start
        && payload.range().count() >= 2
        && payload.has_tree_aux_roots()
        && payload.range().end() <= auth.completed_checkpoint_height
        && payload.range().end() <= handoff)
        .then_some(RangeRequest {
            range: payload.range(),
            anchor_hash: Some(auth.authenticated_hash),
            finalized: true,
            want_tree_aux_roots: true,
            priority: RangePriority::AuthenticateRoots,
        })
}

/// True when both frontiers exist and neither was rebased onto a different hash
/// at the same height.
///
/// Heights may stay put or advance. Same-height hash changes, and any
/// `None`↔`Some` transition, are incompatible with speculative root-auth work.
pub(super) fn root_auth_pipeline_compatible(
    previous: Option<HeaderRootAuthState>,
    next: Option<HeaderRootAuthState>,
) -> bool {
    match (previous, next) {
        (Some(old), Some(new)) => {
            frontier_not_rebased(
                old.authenticated_height,
                old.authenticated_hash,
                new.authenticated_height,
                new.authenticated_hash,
            ) && frontier_not_rebased(
                old.completed_checkpoint_height,
                old.completed_checkpoint_hash,
                new.completed_checkpoint_height,
                new.completed_checkpoint_hash,
            )
        }
        _ => false,
    }
}

fn frontier_not_rebased(
    old_height: block::Height,
    old_hash: block::Hash,
    new_height: block::Height,
    new_hash: block::Hash,
) -> bool {
    new_height > old_height || (new_height == old_height && new_hash == old_hash)
}

#[cfg(test)]
mod tests {
    use super::*;

    fn auth(
        authenticated_height: u32,
        authenticated_hash: u8,
        completed_checkpoint_height: u32,
        completed_checkpoint_hash: u8,
    ) -> HeaderRootAuthState {
        HeaderRootAuthState {
            authenticated_height: block::Height(authenticated_height),
            authenticated_hash: block::Hash([authenticated_hash; 32]),
            completed_checkpoint_height: block::Height(completed_checkpoint_height),
            completed_checkpoint_hash: block::Hash([completed_checkpoint_hash; 32]),
            header_witness: None,
        }
    }

    #[test]
    fn missing_either_side_is_incompatible() {
        let state = auth(1, 1, 4, 4);
        assert!(!root_auth_pipeline_compatible(None, None));
        assert!(!root_auth_pipeline_compatible(None, Some(state)));
        assert!(!root_auth_pipeline_compatible(Some(state), None));
    }

    #[test]
    fn advancing_or_unchanged_frontiers_are_compatible() {
        let previous = auth(1, 1, 4, 4);
        assert!(root_auth_pipeline_compatible(
            Some(previous),
            Some(auth(2, 2, 4, 4))
        ));
        assert!(root_auth_pipeline_compatible(
            Some(previous),
            Some(auth(1, 1, 6, 6))
        ));
        assert!(root_auth_pipeline_compatible(
            Some(previous),
            Some(previous)
        ));
    }

    #[test]
    fn same_height_hash_change_is_a_rebase() {
        let previous = auth(1, 1, 4, 4);
        assert!(!root_auth_pipeline_compatible(
            Some(previous),
            Some(auth(1, 9, 4, 4))
        ));
        assert!(!root_auth_pipeline_compatible(
            Some(previous),
            Some(auth(1, 1, 4, 9))
        ));
    }

    #[test]
    fn stale_successor_witness_degradation_keeps_the_frontier_compatible() {
        let mut previous = auth(4, 4, 5, 5);
        previous.header_witness = Some(crate::zakura::HeaderWitnessState {
            height: block::Height(5),
            hash: block::Hash([5; 32]),
        });
        let next = HeaderRootAuthState {
            header_witness: None,
            ..previous
        };

        assert!(root_auth_pipeline_compatible(Some(previous), Some(next)));
    }
}