netns: factor the netns setup/teardown into distinct services, rather than trying to piggyback network-local-commands
idk what network-local-commands is about, nor network-pre.target. network-pre.target doesn't seem to actually be wanted by anything (?)
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@ -26,9 +26,10 @@ let
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};
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};
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mkNetNsConfig = name: opts: with opts; {
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networking.localCommands = let
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iptables = "${pkgs.iptables}/bin/iptables";
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in-ns = "ip netns exec ${name}";
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systemd.services."netns-${name}" = let
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ip = lib.getExe' pkgs.iproute2 "ip";
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iptables = lib.getExe pkgs.iptables;
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in-ns = "${ip} netns exec ${name}";
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bridgePort = port: proto: ''
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${in-ns} ${iptables} -A PREROUTING -t nat -p ${proto} --dport ${port} -m iprange --dst-range ${netnsPubIpv4} \
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-j DNAT --to-destination ${hostVethIpv4}
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@ -41,55 +42,59 @@ let
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config.sane.ports.ports
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)
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;
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in ''
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ip netns add ${name} || (test -e /run/netns/${name} && echo "${name} already exists")
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# DOCS:
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# - some of this approach is described here: <https://josephmuia.ca/2018-05-16-net-namespaces-veth-nat/>
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# - iptables primer: <https://danielmiessler.com/study/iptables/>
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# create veth pair
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ip link add ${name}-veth-a type veth peer name ${name}-veth-b || echo "${name}-veth-{a,b} aleady exists"
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ip addr add ${hostVethIpv4}/24 dev ${name}-veth-a || echo "${name}-veth-a aleady has IP address"
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ip link set ${name}-veth-a up
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in {
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description = "create a network namespace which will selectively bridge traffic with the init namespace";
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# specifically, we need to set these up before wireguard-wg-*,
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wantedBy = [ "network-pre.target" ];
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before = [ "network-pre.target" ];
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serviceConfig.Type = "oneshot";
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serviceConfig.RemainAfterExit = true;
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script = ''
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${ip} netns add ${name} || (test -e /run/netns/${name} && echo "${name} already exists")
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# DOCS:
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# - some of this approach is described here: <https://josephmuia.ca/2018-05-16-net-namespaces-veth-nat/>
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# - iptables primer: <https://danielmiessler.com/study/iptables/>
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# create veth pair
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${ip} link add ${name}-veth-a type veth peer name ${name}-veth-b || echo "${name}-veth-{a,b} aleady exists"
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${ip} addr add ${hostVethIpv4}/24 dev ${name}-veth-a || echo "${name}-veth-a aleady has IP address"
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${ip} link set ${name}-veth-a up
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# move veth-b into the namespace
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ip link set ${name}-veth-b netns ${name} || echo "${name}-veth-b was already moved into its netns"
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${in-ns} ip addr add ${netnsVethIpv4}/24 dev ${name}-veth-b || echo "${name}-veth-b aleady has IP address"
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${in-ns} ip link set ${name}-veth-b up
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# move veth-b into the namespace
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${ip} link set ${name}-veth-b netns ${name} || echo "${name}-veth-b was already moved into its netns"
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${in-ns} ${ip} addr add ${netnsVethIpv4}/24 dev ${name}-veth-b || echo "${name}-veth-b aleady has IP address"
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${in-ns} ${ip} link set ${name}-veth-b up
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# make it so traffic originating from the host side of the veth
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# is sent over the veth no matter its destination.
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ip rule add from ${hostVethIpv4} lookup ${name} pref 50 || echo "${name} already has ip rules (pref 50)"
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# make it so traffic originating from the host side of the veth
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# is sent over the veth no matter its destination.
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${ip} rule add from ${hostVethIpv4} lookup ${name} pref 50 || echo "${name} already has ip rules (pref 50)"
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# for traffic originating at the host veth to the WAN, use the veth as our gateway
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# not sure if the metric 1002 matters.
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ip route add default via ${netnsVethIpv4} dev ${name}-veth-a proto kernel src ${hostVethIpv4} metric 1002 table ${name} || \
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echo "${name} already has default route"
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# give the default route lower priority
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ip rule add from all lookup local pref 100 || echo "${name}: already has ip rules (pref 100)"
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ip rule del from all lookup local pref 0 || echo "${name}: already removed ip rule of default lookup (pref 0)"
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# for traffic originating at the host veth to the WAN, use the veth as our gateway
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# not sure if the metric 1002 matters.
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${ip} route add default via ${netnsVethIpv4} dev ${name}-veth-a proto kernel src ${hostVethIpv4} metric 1002 table ${name} || \
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echo "${name} already has default route"
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# give the default route lower priority
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${ip} rule add from all lookup local pref 100 || echo "${name}: already has ip rules (pref 100)"
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${ip} rule del from all lookup local pref 0 || echo "${name}: already removed ip rule of default lookup (pref 0)"
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# in order to access DNS in this netns, we need to route it to the VPN's nameservers
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# - alternatively, we could fix DNS servers like 1.1.1.1.
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${in-ns} ${iptables} -A OUTPUT -t nat -p udp --dport 53 -m iprange --dst-range 127.0.0.53 \
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-j DNAT --to-destination ${dns}:53
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'' + (lib.concatStringsSep "\n" bridgeStatements);
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# in order to access DNS in this netns, we need to route it to the VPN's nameservers
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# - alternatively, we could fix DNS servers like 1.1.1.1.
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${in-ns} ${iptables} -A OUTPUT -t nat -p udp --dport 53 -m iprange --dst-range 127.0.0.53 \
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-j DNAT --to-destination ${dns}:53
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'' + (lib.concatStringsSep "\n" bridgeStatements);
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preStop = ''
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${in-ns} ${ip} link del ${name}-veth-b || echo "couldn't delete ${name}-veth-b"
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${ip} link del ${name}-veth-a || echo "couldn't delete ${name}-veth-a"
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${ip} netns delete ${name} || echo "couldn't delete ${name}"
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# restore rules/routes
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${ip} rule del from ${hostVethIpv4} lookup ${name} pref 50 || echo "couldn't delete init -> ${name} rule"
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${ip} route del default via ${netnsVethIpv4} dev ${name}-veth-a proto kernel src ${hostVethIpv4} metric 1002 table ${name} || echo "couldn't delete init > ${name} route"
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# FIXME: if there are other net namespaces active, changing the prefs here may break those!
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${ip} rule add from all lookup local pref 0
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${ip} rule del from all lookup local pref 100
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'';
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};
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# postShutdown = ''
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# ${in-ns} ip link del ${name}-veth-b || echo "couldn't delete ${name}-veth-b"
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# ip link del ${name}-veth-a || echo "couldn't delete ${name}-veth-a"
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# ip netns delete ${name} || echo "couldn't delete ${name}"
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# # restore rules/routes
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# ip rule del from ${veth-host-ip} lookup ${name} pref 50 || echo "couldn't delete init -> ${name} rule"
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# ip route del default via ${veth-local-ip} dev ${name}-veth-a proto kernel src ${veth-host-ip} metric 1002 table ${name} || echo "couldn't delete init > #{name} route"
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# ip rule add from all lookup local pref 0
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# ip rule del from all lookup local pref 100
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# '';
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# specifically, we need to set these up before wireguard-wg-*,
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# whose unit files are BEFORE "network.target", and therefore
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# ordered ambiguously w.r.t. network-local-commands (a dep of "network.target").
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systemd.services.network-local-commands.wantedBy = [ "network-pre.target" ];
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systemd.services.network-local-commands.before = [ "network-pre.target" ];
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# for some reason network-pre doesn't actually get run before network.target by default??
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systemd.targets.network-pre.wantedBy = [ "network.target" ];
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systemd.targets.network-pre.before = [ "network.target" ];
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@ -116,7 +121,7 @@ in
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networking.localCommands = f.networking.localCommands;
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networking.iproute2.rttablesExtraConfig = f.networking.iproute2.rttablesExtraConfig;
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networking.iproute2.enable = f.networking.iproute2.enable;
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systemd.services.network-local-commands = f.systemd.services.network-local-commands;
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systemd.services = f.systemd.services;
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systemd.targets.network-pre = f.systemd.targets.network-pre;
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};
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in take (sane-lib.mkTypedMerge take configs);
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