Add block_network to Sandboxes #1488

cooper-grc · 2025-11-02T21:36:54Z

Setting block_network to True blocks all outbound network traffic from a Sandbox excluding from exposed ports

Summary by cubic

Added a block_network option to Sandboxes/Pods to block all outbound network traffic while still allowing inbound connections to exposed ports. The flag is wired through the API, SDK, and worker to enforce at runtime.

New Features
- New boolean flag: blockNetwork (OpenAPI) / block_network (gRPC, backend, SDK).
- Worker applies IPv4/IPv6 iptables rules to drop outbound traffic from containers.
- Pod/Sandbox constructors and stub creation now accept and propagate block_network.

^{Written for commit 1469875. Summary will update automatically on new commits.}

cubic-dev-ai

4 issues found across 15 files

Prompt for AI agents (all 4 issues)


Understand the root cause of the following 4 issues and fix them.


<file name="pkg/types/backend.go">

<violation number="1" location="pkg/types/backend.go:463">
`BlockNetwork` flag is never propagated to protobuf ContainerRequest, so requests that enable it lose the setting and still allow networking.</violation>
</file>

<file name="pkg/worker/network.go">

<violation number="1" location="pkg/worker/network.go:515">
The DROP rule needs to allow established or related traffic; as written it blocks responses for exposed ports, breaking inbound connectivity when block_network is enabled.</violation>

<violation number="2" location="pkg/worker/network.go:524">
Rule violated: **Prevent Redundant Code Duplication**

The IPv6 prefix/address calculation here duplicates the earlier block in configureContainerNetwork (lines ~437-446). Please extract this logic into a shared helper or reuse the previously computed value to comply with the Prevent Redundant Code Duplication guideline.</violation>

<violation number="3" location="pkg/worker/network.go:528">
This IPv6 DROP rule also needs to exempt established/related traffic; currently it drops reply packets for exposed ports, so inbound IPv6 connections break under block_network.</violation>
</file>

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pkg/types/backend.go

pkg/worker/network.go

cubic-dev-ai

Reviewed changes from recent commits (found 2 issues).

2 issues found across 3 files

Prompt for AI agents (all 2 issues)


Understand the root cause of the following 2 issues and fix them.


<file name="pkg/worker/network.go">

<violation number="1" location="pkg/worker/network.go:515">
Allowing conntrack RELATED traffic lets BlockNetwork containers initiate outbound connections (e.g. FTP active mode) and bypass the egress block.</violation>

<violation number="2" location="pkg/worker/network.go:528">
IPv6 BlockNetwork rule also allows RELATED traffic, letting exposed services initiate outbound connections and defeating the block.</violation>
</file>

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pkg/worker/network.go

cubic-dev-ai

Reviewed changes from recent commits (found 2 issues).

2 issues found across 1 file

Prompt for AI agents (all 2 issues)


Understand the root cause of the following 2 issues and fix them.


<file name="pkg/worker/network.go">

<violation number="1" location="pkg/worker/network.go:515">
Dropping RELATED packets here prevents the container from emitting ICMP/TCP control traffic tied to inbound connections (e.g., PMTU, RST), which will break legitimate clients. Please keep RELATED permitted alongside ESTABLISHED.</violation>

<violation number="2" location="pkg/worker/network.go:528">
We also need to permit conntrack RELATED traffic for IPv6; otherwise ICMPv6 control replies (vital for PMTU/ND) are dropped, breaking inbound connections. Please restore RELATED in the allowed state list.</violation>
</file>

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pkg/worker/network.go

cubic-dev-ai

Reviewed changes from recent commits (found 1 issue).

1 issue found across 1 file

Prompt for AI agents (all 1 issues)


Understand the root cause of the following 1 issues and fix them.


<file name="pkg/worker/network.go">

<violation number="1" location="pkg/worker/network.go:236">
Please handle the error returned by netns.Set(hostNS); if the switch back to the host namespace fails we should return that error rather than continuing in the wrong namespace.</violation>
</file>

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pkg/worker/network.go

cubic-dev-ai

No issues found across 1 file

cooper-grc · 2025-11-05T03:11:39Z

I'm unsure if I should allow RELATED packets. Blocking them breaks ICMP/control messages tied to established connections but it reduces the isolation block_network provides

cubic-dev-ai

No issues found across 1 file

cubic-dev-ai

Reviewed changes from recent commits (found 1 issue).

1 issue found across 3 files

Prompt for AI agents (all 1 issues)


Understand the root cause of the following 1 issues and fix them.


<file name="pkg/types/types.proto">

<violation number="1" location="pkg/types/types.proto:93">
Changing the existing `block_network` field number from 26 to 28 breaks protobuf compatibility; existing clients will interpret wire data incorrectly. Please keep `block_network` at its original tag and assign new numbers to the added fields.</violation>
</file>

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pkg/types/types.proto

cubic-dev-ai

1 issue found across 1 file

Prompt for AI agents (all 1 issues)


Understand the root cause of the following 1 issues and fix them.


<file name="pkg/worker/network.go">

<violation number="1" location="pkg/worker/network.go:542">
Rule violated: **Prevent Redundant Code Duplication**

These three added lines duplicate the existing logic in pkg/worker/network.go:787 that builds the truncated container ID, veth host name, and comment for iptables. Please extract this into a shared helper to avoid violating the Prevent Redundant Code Duplication guideline.</violation>
</file>

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cubic-dev-ai · 2025-11-06T18:11:01Z

pkg/worker/network.go

+		return err
+	}
+
+	truncatedContainerId := containerId[len(containerId)-5:]


Rule violated: Prevent Redundant Code Duplication

These three added lines duplicate the existing logic in pkg/worker/network.go:787 that builds the truncated container ID, veth host name, and comment for iptables. Please extract this into a shared helper to avoid violating the Prevent Redundant Code Duplication guideline.

Prompt for AI agents

Address the following comment on pkg/worker/network.go at line 542: <comment>These three added lines duplicate the existing logic in pkg/worker/network.go:787 that builds the truncated container ID, veth host name, and comment for iptables. Please extract this into a shared helper to avoid violating the Prevent Redundant Code Duplication guideline.</comment> <file context> @@ -539,10 +539,14 @@ func (m *ContainerNetworkManager) setupBlockNetwork(containerId string, request return err } + truncatedContainerId := containerId[len(containerId)-5:] + vethHost := fmt.Sprintf("%s%s", containerVethHostPrefix, truncatedContainerId) + comment := fmt.Sprintf("%s:%s", vethHost, containerId) </file context>

cooper-grc · 2025-11-06T20:24:31Z

Things to consider

Naming
Should block_network be available to just sandboxes or sandboxes and pods. The current implementation has it available to both

Block network

1250e95

cooper-grc marked this pull request as ready for review November 2, 2025 21:37

cooper-grc changed the title ~~Add Block All to Sandboxes~~ Add block_network to Sandboxes Nov 2, 2025

cubic-dev-ai bot reviewed Nov 2, 2025

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Fix drop and propogate proto

003cf98

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Remove established

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Block network for host namespace not container namespace

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Add error handling for namespace search

c68184e

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Allow related packets

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cooper-grc added 2 commits November 5, 2025 14:30

Merge in clip v2

2bfebfd

proto fix

217c94b

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pkg/types/types.proto Show resolved Hide resolved

Add comment to ip tables rule for cleanup

1469875

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cooper-grc requested a review from luke-lombardi November 6, 2025 20:18

Add block_network to Sandboxes #1488

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Add block_network to Sandboxes #1488

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cooper-grc commented Nov 5, 2025

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cooper-grc commented Nov 2, 2025 •

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