Ztunnel

Ztunnel provides an experimental implementation of the ztunnel component of ambient mesh.

Note: istio/ztunnel is currently intended for experimental usage only.

Feature Scope

Ztunnel is intended to be a purpose built implementation of the node proxy in ambient mesh. Part of the goals of this included keeping a narrow feature set, implementing only the bare minimum requirements for ambient. This ensures the project remains simple and high performance.

Explicitly out of scope for ztunnel include:

• Terminating user HTTP traffic
• Terminating user HTTP traffic (its worth repeating)
• Generic extensibility such as ext_authz, WASM, linked-in extensions, Lua, etc.

In general, ztunnel does not aim to be a generic extensible proxy; Envoy is better suited for that task. If a feature is not directly used to implement the node proxy component in ambient mesh, it is unlikely to be accepted.

Building on Non-linux/x86_64

The Ztunnel build enables the fips feature by default, which in turn enables the fips feature on BoringSSL.

FIPS has strict requirements to ensure that compliance is granted only to the exact binary tested. FIPS compliance was granted to an old version of BoringSSL that was tested with Clang 12.0.0.

Installing Clang 12.0.0 on modern environments is at best difficult. For linux x86_64, we work around this problem by shipping the pre-built binaries under vendor/boringssl-fips/linux_x86_64. We then tell the BoringSSL libraries to use this path by setting the BORING_BSSL_PATH environment variable in .cargo/config.toml.

For non-linux/x86_64 platforms, you can disable FIPS by doing the following:

1. Run cargo with the --no-default-features flag (e.g. cargo build --no-default-features).
2. Comment out the BORING_BSSL_* environment variables in .cargo/config.toml. We're actively looking into ways to avoid this step, so it should not be needed in the future.

Some IDEs (such as the Intellij-series) do not support globally applying arguments to cargo. In this case, it is probably easier to remove fips as a default feature in Cargo.toml.

# ...
[features]
default = []
# ...