nginx module produces wrong peer address

[blakeroberts-wk]

Describe your environment

nginx installed as a forward or reverse proxy with the otel instrumentation module installed.

Steps to reproduce

Hit the proxy and inspect the attributes of the generated span.

What is the expected behavior?

The span created by the module when nginx is acting as a proxy should have:

• network.peer.address set to $upstream_addr
• client.address set to $remote_addr

What is the actual behavior?

The span created by the module has the attribute:

• net.peer.ip set to $remote_addr

opentelemetry-cpp-contrib/instrumentation/nginx/src/otel_ngx_module.cpp

Line 50 in 22e7fe2

{"net.peer.ip", "$remote_addr"},

Additional context

• OTel Sem Conv for Networking Attributes: https://opentelemetry.io/docs/specs/semconv/attributes-registry/network/#network-attributes
• $upstream_addr docs: https://nginx.org/en/docs/http/ngx_http_upstream_module.html#var_upstream_addr
• $remote_addr docs: https://nginx.org/en/docs/http/ngx_http_core_module.html#var_remote_addr