etchdns 0.1.0

A caching DNS proxy with advanced security features, WebAssembly hooks, and comprehensive protection mechanisms
Documentation 
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use std::time::{Duration, SystemTime};

use log::{error, warn};
use sieve_cache::SyncSieveCache;

use crate::dns_key::DNSKey;

/// A cached DNS response with an expiration time
#[derive(Clone)]
pub struct CachedResponse {
    /// The raw DNS response data
    pub data: Vec<u8>,

    /// The time when this response expires
    pub expires_at: SystemTime,
}

impl CachedResponse {
    /// Create a new cached response with the given data and TTL
    pub fn new(data: Vec<u8>, ttl: Duration) -> Self {
        let expires_at = SystemTime::now() + ttl;

        Self { data, expires_at }
    }

    /// Check if the response has expired
    pub fn is_expired(&self) -> bool {
        SystemTime::now().duration_since(self.expires_at).is_ok()
    }
}

/// A thread-safe DNS cache using SyncSieveCache
pub type SyncDnsCache = SyncSieveCache<DNSKey, CachedResponse>;

/// Create a new thread-safe DNS cache with the given capacity
pub fn create_dns_cache(capacity: usize) -> SyncDnsCache {
    match SyncSieveCache::<DNSKey, CachedResponse>::new(capacity) {
        Ok(cache) => cache,
        Err(e) => {
            error!("Failed to create DNS cache with requested capacity {capacity}: {e}");
            // Fall back to a smaller size if allocation fails
            let smaller_capacity = std::cmp::max(100, capacity / 2);
            warn!("Falling back to smaller DNS cache capacity: {smaller_capacity}");

            // Try with smaller capacity, if that fails we have a serious problem
            SyncSieveCache::<DNSKey, CachedResponse>::new(smaller_capacity)
                .expect("Critical error: Failed to allocate even minimal DNS cache")
        }
    }
}