The SO_BINDTODEVICE → IP_PKTINFO switch in the previous commit
was a semantic change: the module no longer touches outgoing
routing at all, and several places in the docs and the module's
top-of-file comment still described the old mechanism.
- README.md and debian/control now describe attribution as
reading the ingress ifindex per connection from the kernel's
IP_PKTINFO / IPV6_PKTINFO cmsg, and explicitly call out that
the DSR / maglev return-path constraint is what makes the
change necessary.
- docs/design.md FR-1.1 / FR-1.5 / FR-1.6 are rewritten to
forbid SO_BINDTODEVICE and to describe the cmsg-based lookup.
NFR-6.1 notes these are ordinary unprivileged socket options.
The "Components" / "Composes With" sections and the
"Alternatives Considered" entry are brought in line — and a
new entry records SO_BINDTODEVICE as a rejected alternative
with the exact failure mode seen on an IPng production box.
- docs/config-guide.md already carried the new description;
unchanged here.
- src/ngx_http_ipng_stats_module.c's top-level block comment is
rewritten to match; the section header above init_module goes
from "rebind listen sockets with SO_BINDTODEVICE" to "enable
IP_PKTINFO on listen sockets, resolve ifindexes".
Three SO_BINDTODEVICE mentions deliberately remain in the source
and one in the design doc's alternatives table — all of them
explain that the module *avoids* the option, which is itself
load-bearing documentation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Pim van Pelt
055cf9f830