From 76d4d46b0c711a14decdff408337e806f6c556eb Mon Sep 17 00:00:00 2001
From: r-vdp <ramses@well-founded.dev>
Date: Thu, 7 Nov 2024 18:26:14 +0100
Subject: [PATCH] nixos-rebuild: set SSHOPTS earlier so that we resolve the
 correct hostname

Before, when using things like proxy jumps, we would end up with the hostname of either localhost or the jump host (depending on whether you configure the jumphost in your ssh config file or in the SSHOPTS) instead of the hostname of the target host.

I was running the following command:
```bash
NIX_SSHOPTS='-p 6016 -J username@jumphost' nixos-rebuild --verbose --flake '.#' --target-host localhost --use-remote-sudo --fast build
```

and what was getting built was `nixosConfigurations.<localhost hostname>` instead of `nixosConfigurations.<remote hostname>`, because the SSH connection to determine the hostname didn't have the NIX_SSHOPTS added to it yet.

So I simply moved the logic to set up the tmp dir and set the SSHOPTS a bit higher up.
---
 .../linux/nixos-rebuild/nixos-rebuild.sh      | 38 +++++++++----------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh b/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
index 80dc2055e53b..425cba637675 100755
--- a/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
+++ b/pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh
@@ -427,6 +427,25 @@ if [[ -z $flake && -e /etc/nixos/flake.nix && -z $noFlake ]]; then
     flake="$(dirname "$(readlink -f /etc/nixos/flake.nix)")"
 fi
 
+tmpDir=$(mktemp -t -d nixos-rebuild.XXXXXX)
+
+if [[ ${#tmpDir} -ge 60 ]]; then
+    # Very long tmp dirs lead to "too long for Unix domain socket"
+    # SSH ControlPath errors. Especially macOS sets long TMPDIR paths.
+    rmdir "$tmpDir"
+    tmpDir=$(TMPDIR= mktemp -t -d nixos-rebuild.XXXXXX)
+fi
+
+cleanup() {
+    for ctrl in "$tmpDir"/ssh-*; do
+        ssh -o ControlPath="$ctrl" -O exit dummyhost 2>/dev/null || true
+    done
+    rm -rf "$tmpDir"
+}
+trap cleanup EXIT
+
+SSHOPTS="$NIX_SSHOPTS -o ControlMaster=auto -o ControlPath=$tmpDir/ssh-%n -o ControlPersist=60"
+
 # For convenience, use the hostname as the default configuration to
 # build from the flake.
 if [[ -n $flake ]]; then
@@ -450,23 +469,6 @@ if [[ ! -z "$specialisation" && ! "$action" = switch && ! "$action" = test ]]; t
     exit 1
 fi
 
-tmpDir=$(mktemp -t -d nixos-rebuild.XXXXXX)
-
-if [[ ${#tmpDir} -ge 60 ]]; then
-    # Very long tmp dirs lead to "too long for Unix domain socket"
-    # SSH ControlPath errors. Especially macOS sets long TMPDIR paths.
-    rmdir "$tmpDir"
-    tmpDir=$(TMPDIR= mktemp -t -d nixos-rebuild.XXXXXX)
-fi
-
-cleanup() {
-    for ctrl in "$tmpDir"/ssh-*; do
-        ssh -o ControlPath="$ctrl" -O exit dummyhost 2>/dev/null || true
-    done
-    rm -rf "$tmpDir"
-}
-trap cleanup EXIT
-
 
 # Re-execute nixos-rebuild from the Nixpkgs tree.
 if [[ -z $_NIXOS_REBUILD_REEXEC && -n $canRun && -z $fast ]]; then
@@ -510,8 +512,6 @@ if [ "$action" = edit ]; then
     exit 1
 fi
 
-SSHOPTS="$NIX_SSHOPTS -o ControlMaster=auto -o ControlPath=$tmpDir/ssh-%n -o ControlPersist=60"
-
 # First build Nix, since NixOS may require a newer version than the
 # current one.
 if [[ -n "$rollback" || "$action" = dry-build ]]; then