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netdir: remove duplicate code in param calculation

This commit is contained in:
Nick Mathewson 2023-01-27 13:50:24 -05:00
parent 4e7a552171
commit f6cbd180a1
1 changed files with 31 additions and 23 deletions
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54
crates/tor-netdir/src/hsdir_params.rs
View File

@ -88,38 +88,30 @@ impl HsRingParams {
.ok_or(Error::InvalidConsensus(
"Consensus valid-after did not fall in a time period",
))?;
let cur_period_start = cur_period
.range()
.ok_or(Error::InvalidConsensus(
"HsDir time period in consensus could not be represented as a SystemTime range.",
))?
.start;
let cur_srv = find_srv_for_time(&srvs[..], cur_period_start)
.unwrap_or_else(|| disaster_srv(cur_period));
let main_ring = HsRingParams {
time_period: cur_period,
shared_rand: cur_srv,
};
let main_ring = find_params_for_time(&srvs[..], cur_period)?
.unwrap_or_else(|| disaster_params(cur_period));
// When computing secondary rings, we don't try so many fallback operations:
// if they aren't available, they aren't available.
let mut other_rings = Vec::new();
for period in [cur_period.prev(), cur_period.next()].iter().flatten() {
if let Some(period_range) = period.range() {
if let Some(srv) = find_srv_for_time(&srvs[..], period_range.start) {
other_rings.push(HsRingParams {
time_period: *period,
shared_rand: srv,
});
}
}
}
let other_rings = [cur_period.prev(), cur_period.next()]
.iter()
.flatten()
.flat_map(|period| find_params_for_time(&srvs[..], *period).ok().flatten())
.collect();
Ok((main_ring, other_rings))
}
}
/// Compute ring parameters using a Disaster SRV for this period.
fn disaster_params(period: TimePeriod) -> HsRingParams {
HsRingParams {
time_period: period,
shared_rand: disaster_srv(period),
}
}
/// Compute the "Disaster SRV" for a given time period.
///
/// This SRV is used if the authorities do not list any shared random value for
@ -139,6 +131,22 @@ fn disaster_srv(period: TimePeriod) -> SharedRandVal {
/// recent.
type SrvInfo = (SharedRandVal, std::ops::Range<SystemTime>);
/// Given a list of SrvInfo, return an HsRingParames instance for a given time
/// period, if possible.
fn find_params_for_time(info: &[SrvInfo], period: TimePeriod) -> Result<Option<HsRingParams>> {
let start = period
.range()
.ok_or(Error::InvalidConsensus(
"HsDir time period in consensus could not be represented as a SystemTime range.",
))?
.start;
Ok(find_srv_for_time(info, start).map(|srv| HsRingParams {
time_period: period,
shared_rand: srv,
}))
}
/// Given a list of SrvInfo, return the SharedRandVal (if any) that is the most
/// recent SRV at `when`.
fn find_srv_for_time(info: &[SrvInfo], when: SystemTime) -> Option<SharedRandVal> {