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servo: bridge port 80/53 from ovpns to native using iptables instead of socat

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i should probably narrow the rules to match specifically things destined
for the ovpns address, but for now this should work.
This commit is contained in:
colin
2022-12-09 14:16:48 +00:00
parent a979521a98
commit 2014d5ce77
1 changed files with 32 additions and 10 deletions
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42
hosts/servo/net.nix
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@@ -28,6 +28,8 @@
1900 7359 # DLNA: https://jellyfin.org/docs/general/networking/index.html
4001 # IPFS
];
# this is needed to forward packets from the VPN to the host
boot.kernel.sysctl."net.ipv4.ip_forward" = 1;
# we need to use externally-visible nameservers in order for VPNs to be able to resolve hosts.
networking.nameservers = [
@@ -69,18 +71,38 @@
Type = "oneshot";
RemainAfterExit = true;
ExecStart = with pkgs; writeScript "wg0veth-start" ''
#!${bash}/bin/bash
ExecStart = let
ip = "${pkgs.iproute2}/bin/ip";
in-ns = "${ip} netns exec ovpns";
iptables = "${pkgs.iptables}/bin/iptables";
in pkgs.writeScript "wg0veth-start" ''
#!${pkgs.bash}/bin/bash
# DOCS:
# - some of this approach is described here: <https://josephmuia.ca/2018-05-16-net-namespaces-veth-nat/>
# - iptables primer: <https://danielmiessler.com/study/iptables/>
# create veth pair
${iproute2}/bin/ip link add ovpns-veth-a type veth peer name ovpns-veth-b
${iproute2}/bin/ip addr add 10.0.1.5/24 dev ovpns-veth-a
${iproute2}/bin/ip link set ovpns-veth-a up
${ip} link add ovpns-veth-a type veth peer name ovpns-veth-b
${ip} addr add 10.0.1.5/24 dev ovpns-veth-a
${ip} link set ovpns-veth-a up
# mv veth-b into the ovpns namespace
${iproute2}/bin/ip link set ovpns-veth-b netns ovpns
${iproute2}/bin/ip -n ovpns addr add 10.0.1.6/24 dev ovpns-veth-b
${iproute2}/bin/ip -n ovpns link set ovpns-veth-b up
# forward HTTP traffic, which we need for letsencrypt to work
${iproute2}/bin/ip netns exec ovpns ${socat}/bin/socat TCP4-LISTEN:80,reuseaddr,fork,su=nobody TCP4:10.0.1.5:80 &
${ip} link set ovpns-veth-b netns ovpns
${ip} -n ovpns addr add 10.0.1.6/24 dev ovpns-veth-b
${ip} -n ovpns link set ovpns-veth-b up
# bridge HTTP traffic:
# any external port-80 request sent to the VPN addr will be forwarded to the rootns.
# this exists so LetsEncrypt can procure a cert for the MX over http.
# old socat impl:
# ${in-ns} ${pkgs.socat}/bin/socat TCP4-LISTEN:80,reuseaddr,fork,su=nobody TCP4:10.0.1.5:80 &
${in-ns} ${iptables} -A PREROUTING -t nat -p tcp --dport 80 -j DNAT --to-destination 10.0.1.5:80
${in-ns} ${iptables} -A POSTROUTING -t nat -p tcp --dport 80 -j SNAT --to-source 10.0.1.6
# we also bridge DNS traffic (TODO: test TCP)
${in-ns} ${iptables} -A PREROUTING -t nat -p udp --dport 53 -j DNAT --to-destination 10.0.1.5:53
${in-ns} ${iptables} -A PREROUTING -t nat -p tcp --dport 53 -j DNAT --to-destination 10.0.1.5:53
${in-ns} ${iptables} -A POSTROUTING -t nat -p udp --dport 53 -j SNAT --to-source 10.0.1.6
${in-ns} ${iptables} -A POSTROUTING -t nat -p tcp --dport 53 -j SNAT --to-source 10.0.1.6
'';
ExecStop = with pkgs; writeScript "wg0veth-stop" ''