Egress protocol completeness #3712

Actor egress only carries HTTP(S), TLS passthrough, and DNS. Agents often need more: WebSocket for realtime APIs and remote browsers, SSH for git, database clients, HTTP/3. The only workaround today is a tls_passthrough rule, which skips policy checks inside the connection and only works for TLS.

We should expand on the existing supported egress protocols post v1.0.0.

Today

Supported:

• HTTP/1.1 and HTTP/2, cleartext or HTTPS
• TLS to a host with a tls_passthrough rule
• DNS, for hosts in the actor's policy

Blocked:

• WebSocket (ws://, wss://). Blocked by Add E2E HTTPS egress tests and reject WebSocket upgrades #1634
• CONNECT from the actor. Blocked by atenet-egress: refuse an actor's own CONNECT with 403 #2721
• TLS without SNI, such as HTTPS to an IP address
• Other TCP: SSH, Postgres, Redis, SMTP
• UDP other than DNS, including QUIC/HTTP3
• ICMP, such as ping
• IPv6

See egress-traffic.md for what the actor sees in each case.

cc Bowei Du (@bowei) Lior Lieberman (@LiorLieberman)