atunnel: restrict the actor egress listener to IPv4 - #1042
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atunnel: restrict the actor egress listener to IPv4#1042Yuan Gao (ygao-g) wants to merge 1 commit into
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This was referenced Aug 18, 2026
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The transparent egress listener was opened with net.Listen("tcp",
"0.0.0.0:15001"). Go treats an unspecified address as a wildcard, so
that binds "::" dual-stack and accepts IPv6 connections, but the
original-destination lookup reads only the IPv4 SOL_IP/SO_ORIGINAL_DST.
An IPv6 actor connection was therefore accepted and then failed with no
destination to dial. Open it with "tcp4" through a named helper,
ListenEgressIPv4, so the constraint is visible at the call site and the
connection is refused rather than half-served.
This is a stopgap for the IPv4-only actor network, not the fix: the
IPv6 original-destination lookup is agent-substrate#686 and dual-stack actor
networking is agent-substrate#945. Ingress keeps its family-agnostic wildcard and is
unaffected.
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Fixes #943
The actor egress listener was opened with
net.Listen("tcp", "0.0.0.0:15001").Go treats every unspecified address as a wildcard, so that binds
::dual-stack: the listener has been accepting IPv6 connections all along, and
TCPOriginalDestinationcannot resolve them because it reads only the IPv4SOL_IP/SO_ORIGINAL_DST. Such a connection is accepted and then fails.Egress now opens through
atunnel.ListenEgressIPv4, where the network stringdecides the family rather than an address that never did; the family is in the
name so the constraint is visible at the call site while the IPv6 work is in
flight.
This does not hold IPv6-only clusters back: the actor leg is IPv4 link-local by
construction (
ateomnet.ActorVethIP, IPv4-family nftables), so nothing thatworks today changes. Widening egress in earnest needs actor networking to gain
IPv6 (#945) and an
IP6T_SO_ORIGINAL_DSTlookup (#686). The ingress flagdefault is spelled
:443to record that it is deliberately dual-stack, which isa comment on existing behavior rather than a change to it.
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