Block outbound HTTP requests to specified IP ranges before TCP handshake
using libcurl CURLOPT_OPENSOCKETFUNCTION callback. Fires after DNS
resolution, reads resolved IP directly from sockaddr, does bitwise CIDR
comparison. Fail-closed: unknown address families are blocked.
--block_private_networks blocks RFC1918, localhost, link-local, ULA.
--block_cidrs blocks additional comma-separated CIDRs.
IPv4-mapped IPv6 (::ffff:x.x.x.x) is unwrapped to prevent bypass.
Uses libcurl's websocket capabilities to add support for WebSocket.
Depends on https://github.com/lightpanda-io/zig-v8-fork/pull/167
Issue: https://github.com/lightpanda-io/browser/issues/1952
This is a WIP because it currently uses the same connection pool used for all
HTTP requests. It would be pretty easy for a page to starve the pool and block
any progress.
We previously stored the *Transfer inside of the easy's private data. We now
store the *Connection, and a Connection now has a `transport` field which is
a union for `http: *Transfer` or `websocket: *Websocket`.
