chore(firewall): split apart iptables specific code in internal/firewall/iptables

internal/firewall/iptables/firewall.go

@@ -0,0 +1,36 @@
+package iptables
+
+import (
+	"context"
+	"sync"
+)
+
+type Config struct {
+	runner         CmdRunner
+	logger         Logger
+	iptablesMutex  sync.Mutex
+	ip6tablesMutex sync.Mutex
+
+	// Fixed state
+	ipTables  string
+	ip6Tables string
+}
+
+func New(ctx context.Context, runner CmdRunner, logger Logger) (*Config, error) {
+	iptables, err := checkIptablesSupport(ctx, runner, "iptables", "iptables-nft", "iptables-legacy")
+	if err != nil {
+		return nil, err
+	}
+
+	ip6tables, err := findIP6tablesSupported(ctx, runner)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Config{
+		runner:    runner,
+		logger:    logger,
+		ipTables:  iptables,
+		ip6Tables: ip6tables,
+	}, nil
+}