Who and why: operators front an application's outbound traffic to deny loopback, private, link-local, and metadata addresses even when an allowed hostname resolves to them.
MITM required? No. Egress policy runs after the connection rule and before any upstream dial, including on mitm:false splices.
Use ordered egress[] entries to make narrow exceptions before broad denies. Every address returned by the one pinned DNS resolution must be allowed; a mixed public/private response is rejected. An empty list or fall-through denies.
You get DNS-rebinding resistance and 403 ERR_FORWARDING_DENIED audit events. You do not get a replacement for the firewall that blocks clients from bypassing the proxy.
Next: configure egress or follow the Docker tutorial.
If the workload cannot be configured with HTTP_PROXY/HTTPS_PROXY, the intended transparent deployment steers its traffic with nftables. See Transparent interception for the REDIRECT and TPROXY choices.