First alpha release of PowerDNS Recursor 5.5.0

[omoerbeek]

https://blog.powerdns.com/2026/08/13/first-alpha-release-of-powerdns-recursor-5.5.0

[paddg]

Hi,

I am migrating the RPM package for PowerDNS Recursor to Meson (RPM spec file ). I used AI assistance while investigating this issue. I verified the workaround (see bellow) with a successful offline build.

The build runs in an offline distribution build environment (OBS). It failed during the Rust build although the source package contains a pre-generated Cargo vendor/ directory and .cargo/config.toml.

The AI provided a patch as a workaround. From this point on, the report is AI-generated. I hope that's okay.

Offline Meson builds do not use vendored Cargo dependencies.

When building the Recursor with Meson in an offline distribution build environment, the Rust build fails because rec-rust-lib/rust/build_recrust invokes cargo build without explicitly selecting the vendored dependencies.

Our source package includes a Cargo vendor/ directory and a .cargo/config.toml, but the Meson/Ninja custom target does not reliably use this configuration. Cargo then tries to access crates.io:

Updating crates.io index
warning: spurious network error: Could not resolve host: index.crates.io

error: failed to get `base64` as a dependency of package `recrust`
Caused by:
  unable to update registry `crates-io`

As a downstream workaround, we patch build_recrust to explicitly configure Cargo to use the vendored sources and build offline:

--- a/rec-rust-lib/rust/build_recrust
+++ b/rec-rust-lib/rust/build_recrust
@@ -36 +36,4 @@
-$CARGO build --profile ${CARGO_PROFILE} ${CARGO_CONFIG} $RUST_TARGET --target-dir=$builddir/target --manifest-path $srcdir/Cargo.toml --locked $features
+$CARGO build --offline \
+    --config "source.crates-io.replace-with=\"vendored-sources\"" \
+    --config "source.vendored-sources.directory=\"$srcdir/vendor\"" \
+    --profile ${CARGO_PROFILE} ${CARGO_CONFIG} $RUST_TARGET --target-dir=$builddir/target --manifest-path $srcdir/Cargo.toml --locked $features

This makes the offline build succeed.

We are providing the patch as an illustration of the issue, not necessarily as the preferred upstream solution. Since a normal Git checkout might not contain a vendor/ directory, could build_recrust provide an upstream-supported mechanism to pass Cargo configuration or additional Cargo arguments for offline/vendored builds?

[omoerbeek]

The package build environments that force offline builds we have seen sofar take care of this in other ways. For example, on OpenBSD, a .cargo file is created in the build dir that includes (taking an example of a rec 5.4.5 build):

...
[net]
offline = true
[source.modcargo]
directory = '/usr/ports/pobj/powerdns-recursor-5.4.5/pdns-recursor-5.4.5/modcargo-crates'
[source.crates-io]
replace-with = 'modcargo'
...

The issue with the proposed patch is that it would likely interfere with that mechanism.

[paddg]

Hello Otto,

Thank you, that makes sense.

The root cause was that Cargo did not find its configuration when invoked by Meson from its out-of-tree build directory. We have fixed this in our RPM spec file by placing the Cargo configuration and vendor directory where Cargo can discover them:

cp -a rec-rust-lib/rust/.cargo x86_64-suse-linux/
ln -s ../rec-rust-lib/rust/vendor x86_64-suse-linux/vendor

Winfried