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netns-isolation: separate host and netns setup

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- Improves readability

- `netns exec ...` (called via `netnsIptables`) incurs a large
  overhead: In addition to netns switching, a mount namespace
  is setup and populated with the contents of /etc/netns/<ns>/.
  Instead, simply run `nsenter`.
This commit is contained in:
Erik Arvstedt 2021-11-08 12:45:29 +01:00
parent cb6e5ef702
commit f58d67677e
No known key found for this signature in database
GPG Key ID: 33312B944DD97846
1 changed files with 41 additions and 29 deletions
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70
modules/netns-isolation.nix
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@ -155,9 +155,42 @@ in {
veth = "nb-veth-${toString v.id}";
peer = "nb-veth-br-${toString v.id}";
inherit (v) netnsName;
ipNetns = "${ip} -n ${netnsName}";
netnsIptables = "${ip} netns exec ${netnsName} ${config.networking.firewall.package}/bin/iptables";
nsenter = "${pkgs.utillinux}/bin/nsenter";
allowedAddresses = concatMapStringsSep "," (available: netns.${available}.address) v.availableNetns;
setup = ''
${ip} netns add ${netnsName}
${ip} link add ${veth} type veth peer name ${peer}
${ip} link set ${veth} netns ${netnsName}
# The peer link is never used directly, so don't auto-assign an IPv6 address
echo 1 > /proc/sys/net/ipv6/conf/${peer}/disable_ipv6
${ip} link set ${peer} up
${ip} link set ${peer} master nb-br
exec ${nsenter} --net=/run/netns/${netnsName} ${script "in-netns" setupInNetns}
'';
setupInNetns = ''
${ip} link set lo up
${ip} addr add ${v.address}/24 dev ${veth}
${ip} link set ${veth} up
${ip} route add default via ${bridgeIp}
${iptables} -w -P INPUT DROP
${iptables} -w -A INPUT -s 127.0.0.1,${bridgeIp},${v.address} -j ACCEPT
# allow return traffic to outgoing connections initiated by the service itself
${iptables} -w -A INPUT -m conntrack --ctstate ESTABLISHED -j ACCEPT
'' + optionalString (config.services.${n}.enforceTor or false) ''
${iptables} -w -P OUTPUT DROP
${iptables} -w -A OUTPUT -d 127.0.0.1,${bridgeIp},${v.address} -j ACCEPT
'' + optionalString (v.availableNetns != []) ''
${iptables} -w -A INPUT -s ${allowedAddresses} -j ACCEPT
${iptables} -w -A OUTPUT -d ${allowedAddresses} -j ACCEPT
'';
script = name: src: pkgs.writers.writeDash name ''
set -e
${src}
'';
in {
"${n}".serviceConfig.NetworkNamespacePath = "/var/run/netns/${netnsName}";
@ -166,29 +199,11 @@ in {
after = [ "nb-netns-bridge.service" ];
requiredBy = [ "${n}.service" ];
before = requiredBy;
script = ''
${ip} netns add ${netnsName}
${ipNetns} link set lo up
${ip} link add ${veth} type veth peer name ${peer}
${ip} link set ${veth} netns ${netnsName}
${ipNetns} addr add ${v.address}/24 dev ${veth}
# The peer link is never used directly, so don't auto-assign an IPv6 address
echo 1 > /proc/sys/net/ipv6/conf/${peer}/disable_ipv6
${ip} link set ${peer} up
${ipNetns} link set ${veth} up
${ip} link set ${peer} master nb-br
${ipNetns} route add default via ${bridgeIp}
${netnsIptables} -w -P INPUT DROP
${netnsIptables} -w -A INPUT -s 127.0.0.1,${bridgeIp},${v.address} -j ACCEPT
# allow return traffic to outgoing connections initiated by the service itself
${netnsIptables} -w -A INPUT -m conntrack --ctstate ESTABLISHED -j ACCEPT
'' + optionalString (config.services.${n}.enforceTor or false) ''
${netnsIptables} -w -P OUTPUT DROP
${netnsIptables} -w -A OUTPUT -d 127.0.0.1,${bridgeIp},${v.address} -j ACCEPT
'' + optionalString (v.availableNetns != []) ''
${netnsIptables} -w -A INPUT -s ${allowedAddresses} -j ACCEPT
${netnsIptables} -w -A OUTPUT -d ${allowedAddresses} -j ACCEPT
'';
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
ExecStart = script "setup" setup;
};
# Link deletion is implicit in netns deletion, but it sometimes only happens
# after `netns delete` finishes. Add an extra `link del` to ensure that
# the link is deleted before the service stops, which is needed for service
@ -197,10 +212,7 @@ in {
${ip} netns delete ${netnsName}
${ip} link del ${peer} 2> /dev/null || true
'';
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
};
};
in foldl (services: n: