v0.3.0's listen wrapper treated every listen beyond the first at a
given sockaddr as a skip-core "duplicate", which was correct for
two `listen 80 device=X/Y;` lines in one server block but broke on
the real deployment pattern where every server-*.conf pulls in the
same `include listens.conf;`. Symptoms:
* every server block after the first ended up with no listen
directive processed, so nginx assigned them the default
`*:80`, producing a flood of "conflicting server name"
warnings and attaching every server block to an unrelated
wildcard bind;
* the bindings list grew linearly with the number of server
blocks, so init_module tried to create (server_blocks) ×
(devices × families) listening sockets and hit EMFILE.
Replace the single dedup with two independent checks:
* listens_seen is a (cscf, sockaddr) ledger. The core listen
handler is invoked at most once per (server block, sockaddr),
matching nginx's own duplicate check so server-block N just
attaches its cscf to the existing address via
ngx_http_add_server.
* `bind` is added only for the first global occurrence of each
sockaddr; subsequent cscfs inherit opt.set/opt.bind from the
first, which is what keeps nginx's "duplicate listen options"
check happy across server blocks.
* bindings dedup on (sockaddr, device) globally, so init_module
creates one socket per unique pair regardless of how many
server blocks reference it.
Add a regression test at tests/01-module/ that wires three server
blocks to the same ipng-listens.inc and asserts that nginx -t is
clean and exactly four sockets are bound on port 8080.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Nginx's config-level duplicate-listen check rejected the
documented pattern of `listen 80 device=X ipng_source_tag=A;
listen 80 device=Y ipng_source_tag=B;` with "a duplicate listen
0.0.0.0:80", and even when the dedup was bypassed the kernel
refused the second bind() because the first socket was already
holding the port without SO_BINDTODEVICE.
The listen wrapper now detects same-sockaddr duplicates before
the core handler sees them and records them with `needs_clone=1`.
In init_module, phase 1 clones an ngx_listening_t for each such
duplicate, phase 3 closes every inherited naked fd, and phase 4
rebinds every target with SO_REUSEADDR + SO_REUSEPORT +
SO_BINDTODEVICE set before bind(). SO_REUSEPORT keeps
`nginx -s reload` from colliding with the still-bound sockets
held by old workers during graceful drain; IPV6_V6ONLY matches
nginx's default so the IPv6 listen doesn't claim the IPv4
wildcard and collide with sibling IPv4-specific listens.
Restructure 01-module to cover the pattern end-to-end: four
device-pinned listens on port 8080 (eth1 shares tag `tag1`
across v4 and v6; eth2 splits into `tag2-v4` / `tag2-v6`),
clients and server both get IPv6 addresses, and a new
"Per-(device, family) request count accuracy" case proves that
10 requests on each of the four combinations yields tag1=20,
tag2-v4=10, tag2-v6=10. Mgmt/direct traffic moves to port 9180
so it no longer clashes with the shared-port wildcards.
Document the constraint in docs/user-guide.md: all listens on
a given port must carry `device=`, and direct traffic belongs
on a separate port.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- ipng_stats_logtail now accepts an optional if=$variable parameter
that suppresses log lines when the variable is empty or "0",
following the same semantics as nginx's access_log if=. The
condition is checked before format rendering for zero overhead on
filtered requests. Filtered requests are still counted by stats.
- Log format examples updated to include $scheme for http/https
visibility, and renamed to ipng_stats_logtail to match production.
- Robot test added for the if= filter (19 tests, 19 pass).
- FR-8.5 added to design doc for the if= semantics.
Full implementation of the nginx dynamic module with:
- SO_BINDTODEVICE-based per-interface traffic attribution
- Per-worker lock-free counters flushed to shared memory
- Prometheus text and JSON scrape endpoint at configurable location
- UDP-only global logtail (ipng_stats_logtail) for fire-and-forget
access log streaming
- $ipng_source_tag nginx variable for use in log_format/map
- Histogram buckets, EWMA rate gauges, zone meta-metrics
- Debian packaging (libnginx-mod-http-ipng-stats)
- Robot Framework end-to-end tests via containerlab
- SPDX Apache-2.0 headers on all source files
