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feat: always use preloaded DNS results

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Otherwise if DNS server returns incorrect results,
we may never try preloaded DNS results.
For example, we may get our first results
from a captive portal.

To test, add `127.0.0.1 example.org`
and try to create an account.
Without this change we only try 127.0.0.1 and fail.
With this change preloaded DNS results are tried as well.
This commit is contained in:
link2xt
2024-08-25 01:53:16 +00:00
parent 36e5e964e5
commit 137ee9334c
1 changed files with 11 additions and 17 deletions
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28
src/net/dns.rs
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@@ -108,6 +108,10 @@ pub(crate) async fn update_connect_timestamp(
Ok(())
}
/// Preloaded DNS results that can be used in case of DNS server failures.
///
/// See <https://support.delta.chat/t/no-dns-resolution-result/2778> and
/// <https://github.com/deltachat/deltachat-core-rust/issues/4920> for reasons.
static DNS_PRELOAD: Lazy<HashMap<&'static str, Vec<IpAddr>>> = Lazy::new(|| {
HashMap::from([
(
@@ -501,21 +505,6 @@ static DNS_PRELOAD: Lazy<HashMap<&'static str, Vec<IpAddr>>> = Lazy::new(|| {
])
});
/// Load hardcoded cache if everything else fails.
///
/// See <https://support.delta.chat/t/no-dns-resolution-result/2778> and
/// <https://github.com/deltachat/deltachat-core-rust/issues/4920> for reasons.
///
/// In the future we may pre-resolve all provider database addresses
/// and build them in.
fn load_hardcoded_cache(hostname: &str, port: u16) -> Vec<SocketAddr> {
if let Some(ips) = DNS_PRELOAD.get(hostname) {
ips.iter().map(|ip| SocketAddr::new(*ip, port)).collect()
} else {
Vec::new()
}
}
async fn lookup_cache(
context: &Context,
host: &str,
@@ -631,8 +620,13 @@ pub(crate) async fn lookup_host_with_cache(
}
}
if resolved_addrs.is_empty() {
return Ok(load_hardcoded_cache(hostname, port));
if let Some(ips) = DNS_PRELOAD.get(hostname) {
for ip in ips {
let addr = SocketAddr::new(*ip, port);
if !resolved_addrs.contains(&addr) {
resolved_addrs.push(addr);
}
}
}
}