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netns: remove addresses from loopback device

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Colin
2025-07-07 20:19:00 +00:00
parent 48bd6d304f
commit cf38651e8d
1 changed files with 11 additions and 1 deletions
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12
modules/netns.nix
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@@ -87,6 +87,10 @@ let
"${ip} netns delete ${name}"
];
};
# loopback is tricky:
# - we _don't_ want a 127.0.0.1 address, in order that we can forward DNS queries to the outer NS.
# - we _do_ want a `lo` device, as local communications within the netns will use it as source:
# - e.g. `ip route get 10.0.1.6` will show `dev lo` even if `lo` is down.
systemd.services."netns-${name}-lo" = {
description = "bring loopback device online in '${name}' network namespace";
wantedBy = [ "netns-${name}.target" ];
@@ -96,7 +100,13 @@ let
serviceConfig.Type = "oneshot";
serviceConfig.RemainAfterExit = true;
serviceConfig.NetworkNamespacePath = "/run/netns/${name}";
serviceConfig.ExecStart = "${ip} link set lo up";
script = ''
${ip} link set lo up
# N.B.: these addresses are implicitly assigned when the interface transitions down -> up.
# so unfortunately, we have a blip here where the addresses are briefly assigned, then removed.
${ip} addr del 127.0.0.1/8 dev lo || echo "lo IPv4 address already removed"
${ip} addr del ::1/128 dev lo || echo "lo IPv6 address already removed"
'';
serviceConfig.ExecStop = "${ip} link set lo down";
};
systemd.services."netns-${name}-veth" = {