{"version":"2.1.236","anchor":"sandbox-proxy-no-longer-writes-to-sockets-that-have-gone-awa","canonical_anchor":"sandbox-proxy-no-longer-writes-to-sockets-that-have-gone-awa","heading":"Sandbox proxy no longer writes to sockets that have gone away","tier":"notice","area":"Sandbox","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.236\/e\/sandbox-proxy-no-longer-writes-to-sockets-that-have-gone-awa","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.236","markdown":"### Sandbox proxy no longer writes to sockets that have gone away\n\nThe sandbox network proxy handles clients that disconnect mid-request instead of writing into dead sockets.\n\n**What**\n\nThe local network proxy used for sandboxed sessions now copes with clients that disconnect, are torn down, or flood it during connection setup, instead of writing responses into a dead socket. Before it emits any status response it re-checks that the socket is still writable and drops the decision if it is not, and it tears both ends of a failed tunnel down together.\n\n**Details**\n\n- Data a client sends before the tunnel is established is captured and capped at 65536 bytes; exceeding the cap destroys the connection, logged as `CONNECT client exceeded pre-establishment capture cap; destroying`.\n- Bytes captured during setup are replayed into the request buffer once the connection is established.\n- Any socket error destroys the client socket.\n- The writable check guards the 407 authentication-required, 403 forbidden, 200 tunnel-established and 502 bad-gateway responses, including the 403 that carries the `\"X-Proxy-Error\": \"blocked-by-allowlist\"` header when a host is not on the allowlist.\n- Once a connection is established, half-open tunnels are permitted, so one direction closing no longer kills the other.\n\n**Evidence**\n\n`CONNECT client exceeded pre-establishment capture cap; destroying`, `\"X-Proxy-Error\": \"blocked-by-allowlist\"`\n\n- Area: Sandbox\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 2\/5"}