From a8bdb4fe15d6c80fe20c270f902a246fd2dcf690 Mon Sep 17 00:00:00 2001
From: Benedikt Peetz <benedikt.peetz@b-peetz.de>
Date: Wed, 25 Dec 2024 16:13:02 +0100
Subject: build(scripts/mk_network_config): Init

This has been taken directly from `nixos-infect` (which rather
under-maintained, sadly).
Currently, it is extremely useful to generate the `networking.nix`
config for new hosts.
---
 scripts/mk_network_config.sh | 86 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100755 scripts/mk_network_config.sh

diff --git a/scripts/mk_network_config.sh b/scripts/mk_network_config.sh
new file mode 100755
index 0000000..3c853fb
--- /dev/null
+++ b/scripts/mk_network_config.sh
@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+
+# Taken from: https://github.com/elitak/nixos-infect
+set -e -o pipefail
+
+makeNetworkingConf() {
+    # XXX It'd be better if we used procfs for all this...
+    local IFS=$'\n'
+    eth0_name=$(ip address show | grep '^2:' | awk -F': ' '{print $2}')
+    eth0_ip4s=$(ip address show dev "$eth0_name" | grep 'inet ' | sed -r 's|.*inet ([0-9.]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|')
+    eth0_ip6s=$(ip address show dev "$eth0_name" | grep 'inet6 ' | sed -r 's|.*inet6 ([0-9a-f:]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|' || true)
+    gateway=$(ip route show dev "$eth0_name" | grep default | sed -r 's|default via ([0-9.]+).*|\1|')
+    gateway6=$(ip -6 route show dev "$eth0_name" | grep default | sed -r 's|default via ([0-9a-f:]+).*|\1|' || true)
+    ether0=$(ip address show dev "$eth0_name" | grep link/ether | sed -r 's|.*link/ether ([0-9a-f:]+) .*|\1|')
+
+    eth1_name=$(ip address show | grep '^3:' | awk -F': ' '{print $2}') || true
+    if [ -n "$eth1_name" ]; then
+        eth1_ip4s=$(ip address show dev "$eth1_name" | grep 'inet ' | sed -r 's|.*inet ([0-9.]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|')
+        eth1_ip6s=$(ip address show dev "$eth1_name" | grep 'inet6 ' | sed -r 's|.*inet6 ([0-9a-f:]+)/([0-9]+).*|{ address="\1"; prefixLength=\2; }|' || true)
+        ether1=$(ip address show dev "$eth1_name" | grep link/ether | sed -r 's|.*link/ether ([0-9a-f:]+) .*|\1|')
+        interfaces1=$(
+            cat <<EOF
+      $eth1_name = {
+        ipv4.addresses = [$(for a in "${eth1_ip4s[@]}"; do echo -n "
+          $a"; done)
+        ];
+        ipv6.addresses = [$(for a in "${eth1_ip6s[@]}"; do echo -n "
+          $a"; done)
+        ];
+        };
+EOF
+        )
+        extraRules1="ATTR{address}==\"${ether1}\", NAME=\"${eth1_name}\""
+    else
+        interfaces1=""
+        extraRules1=""
+    fi
+
+    readarray nameservers < <(grep ^nameserver /etc/resolv.conf | sed -r \
+        -e 's/^nameserver[[:space:]]+([0-9.a-fA-F:]+).*/"\1"/' \
+        -e 's/127[0-9.]+/8.8.8.8/' \
+        -e 's/::1/8.8.8.8/')
+
+    if [[ $eth0_name == eth* ]]; then
+        predictable_inames="usePredictableInterfaceNames = lib.mkForce false;"
+    else
+        predictable_inames="usePredictableInterfaceNames = lib.mkForce true;"
+    fi
+    cat <<EOF
+{ lib, ... }: {
+  # This file was populated at runtime with the networking
+  # details gathered from the active system.
+  networking = {
+    nameservers = [ ${nameservers[@]} ];
+    defaultGateway = "${gateway}";
+    defaultGateway6 = {
+      address = "${gateway6}";
+      interface = "${eth0_name}";
+    };
+    dhcpcd.enable = false;
+    $predictable_inames
+    interfaces = {
+      $eth0_name = {
+        ipv4.addresses = [$(for a in "${eth0_ip4s[@]}"; do echo -n "
+          $a"; done)
+        ];
+        ipv6.addresses = [$(for a in "${eth0_ip6s[@]}"; do echo -n "
+          $a"; done)
+        ];
+        ipv4.routes = [ { address = "${gateway}"; prefixLength = 32; } ];
+        ipv6.routes = [ { address = "${gateway6}"; prefixLength = 128; } ];
+      };
+      $interfaces1
+    };
+  };
+  services.udev.extraRules = ''
+    ATTR{address}=="${ether0}", NAME="${eth0_name}"
+    $extraRules1
+  '';
+}
+EOF
+}
+
+makeNetworkingConf
+
+# vim: ft=sh
-- 
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