Per-VIP, per-device traffic counters for nginx. Ships as a dynamic nginx module and a Debian package that loads into stock upstream nginx on Debian Trixie.

The module attributes every HTTP request to the interface it arrived on, reading the ingress ifindex per connection from the kernel's IP_PKTINFO / IPV6_PKTINFO cmsg. Listening sockets stay plain wildcards, so outgoing packets follow the normal routing table — which is what makes this safe for DSR / maglev deployments where the SYN arrives via a GRE tunnel and the SYN-ACK must leave via the default route. Counters — requests, status codes, bytes, latency histograms — plus point-in-time gauges of requests currently in flight (active, reading, writing) are exposed as Prometheus text or JSON from a single HTTP scrape endpoint, filtered per-source. This is useful for any deployment where traffic arrives on distinct interfaces — GRE tunnels, VLANs, bonded links, or plain ethernet — and per-interface observability is needed.

Without any device=/ipng_source_tag= parameters, the module still counts and exposes per-VIP traffic under the configurable default source tag (direct), which makes it a useful plain observability module for any nginx host.

See docs/design.md for the full design, including the attribution model, data flow, and requirements.

Quick start

make install-deps      # install build and test dependencies (apt)
make build             # build the .so out-of-tree
make pkg-deb           # build a .deb package
make robot-test        # run end-to-end tests via containerlab

Installing

sudo dpkg -i build/*.deb

The package installs the .so into /usr/lib/nginx/modules, drops a load_module stanza into /etc/nginx/modules-enabled/, and runs nginx -t before completing.

Configuring

See docs/user-guide.md for an end-to-end walkthrough and docs/config-guide.md for the directive and listen parameter reference.

License

Apache-2.0. See LICENSE.

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