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fix(egress): switch mitmproxy to connection_strategy=eager #974

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fix(egress): switch mitmproxy to connection_strategy=eager #974

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2ae0422
fix(egress): switch mitmproxy to connection_strategy=eager
Pangjiping Jun 4, 2026
b7b15c0
chore(egress): symlink /egress to new binary path for backward compat…
Pangjiping Jun 4, 2026
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3 changes: 2 additions & 1 deletion components/egress/Dockerfile
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Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,8 @@ COPY --from=builder /out/opensandbox-supervisor /opt/opensandbox-egress/supervis
COPY components/egress/scripts/cleanup.sh /opt/opensandbox-egress/cleanup.sh
RUN chmod 0755 /opt/opensandbox-egress/cleanup.sh \
/opt/opensandbox-egress/egress \
/opt/opensandbox-egress/supervisor
/opt/opensandbox-egress/supervisor \
&& ln -s /opt/opensandbox-egress/egress /egress

COPY components/egress/mitmscripts /var/egress/mitmscripts

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15 changes: 12 additions & 3 deletions components/egress/pkg/mitmproxy/launch.go
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Expand Up @@ -107,9 +107,18 @@ func Launch(cfg Config) (*Running, error) {
// Stream large bodies instead of buffering them in memory (OOM prevention).
args = append(args, "--set", "stream_large_bodies=1m")

// Lazy connection strategy: defer upstream connection until the request is fully received,
// which avoids unnecessary connections for blocked/filtered requests.
args = append(args, "--set", "connection_strategy=lazy")
// Eager connection strategy: open the upstream connection alongside the client
// connection so mitm's IO loop continuously observes upstream FIN/RST. Lazy
// defers the upstream open until the full request is buffered and checks the
// upstream pool per-request; on h1 keepalive sessions this exposes a stale-
// connection race where the second request (e.g. POST /git-upload-pack right
// after GET /info/refs) picks an upstream conn the peer has already closed,
// surfacing as a silent transport error with no fatal output on the client.
// Eager trades a wasted TCP/TLS handshake for the small fraction of requests
// denied by the egress addon — acceptable because a denied flow already short-
// circuits with `flow.response = ...` before any HTTP write reaches upstream,
// so the upstream still sees no path/method/headers from the denied request.
args = append(args, "--set", "connection_strategy=eager")

// Transparent mode redirects TCP to IP addresses. Clients connecting to IPs
// do not send SNI, so upstream TLS cert hostname verification fails with
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