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Fix invocation of iptables if redirection fails #11

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Fix invocation of iptables if redirection fails #11

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56800d0
Fix invocation of iptables if redirection fails
markusboehme Dec 12, 2025
70b06c9
Ignore redirection error if target already exists
markusboehme Dec 12, 2025
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2 changes: 1 addition & 1 deletion internal/iptables/alternatives.go
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Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,7 @@ func (s symlinkSelector) UseMode(ctx context.Context, mode Mode) error {
_ = os.RemoveAll(cmdPath)

if err := os.Symlink(xtablesForModePath, cmdPath); err != nil {
return fmt.Errorf("creating %s symlink for mode %s: %v", cmd, modeStr, err)
return fmt.Errorf("creating %s symlink for mode %s: %w", cmd, modeStr, err)
}
}

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11 changes: 10 additions & 1 deletion main.go
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Expand Up @@ -39,8 +39,10 @@ import (
"context"
"errors"
"fmt"
"io/fs"
"os"
"os/exec"
"path"

"github.com/kubernetes-sigs/iptables-wrappers/internal/iptables"
)
Expand All @@ -67,10 +69,17 @@ func main() {

selector := iptables.BuildAlternativeSelector(sbinPath)
if err := selector.UseMode(ctx, mode); err != nil {
fmt.Fprintf(os.Stderr, "Unable to redirect iptables binaries. (Are you running in an unprivileged pod?): %s\n", err)
// Ignore redirection error if target already exists. This may happen when
// multiple iptables-wrappers are racing each other or the filesystem is
// mounted read-only.

@danwinship danwinship Mar 14, 2026

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If the target already exists and the filesystem is read-only then why was iptables-wrapper present at all?

Leave the comment about racing but the part about read-only doesn't seem like it makes sense to me.

if !errors.Is(err, fs.ErrExist) {
fmt.Fprintf(os.Stderr, "Unable to redirect iptables binaries. (Are you running in an unprivileged pod?): %s\n", err)
}

// fake it, though this will probably also fail if they aren't root
binaryPath = iptables.XtablesPath(sbinPath, mode)
args = os.Args
args[0] = path.Base(args[0])

@danwinship danwinship Mar 14, 2026

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What problem are you seeing exactly?

xtables already handles this:

	const char *cmd = basename(*argv);

}

cmdIPTables := exec.CommandContext(ctx, binaryPath, args...)
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