package netfilterHelper import ( "fmt" "github.com/coreos/go-iptables/iptables" "strconv" ) type PortRemap struct { IPTables *iptables.IPTables ChainName string From uint16 To uint16 Enabled bool } func (r *PortRemap) ForceEnable() error { err := r.IPTables.ClearChain("nat", r.ChainName) if err != nil { return fmt.Errorf("failed to clear chain: %w", err) } err = r.IPTables.AppendUnique("nat", r.ChainName, "-p", "udp", "--dport", strconv.Itoa(int(r.From)), "-j", "REDIRECT", "--to-port", strconv.Itoa(int(r.To))) if err != nil { return fmt.Errorf("failed to create rule: %w", err) } err = r.IPTables.InsertUnique("nat", "PREROUTING", 1, "-j", r.ChainName) if err != nil { return fmt.Errorf("failed to linking chain: %w", err) } r.Enabled = true return nil } func (r *PortRemap) Disable() []error { var errs []error err := r.IPTables.DeleteIfExists("nat", "PREROUTING", "-j", r.ChainName) if err != nil { errs = append(errs, fmt.Errorf("failed to unlinking chain: %w", err)) } err = r.IPTables.ClearAndDeleteChain("nat", r.ChainName) if err != nil { errs = append(errs, fmt.Errorf("failed to delete chain: %w", err)) } r.Enabled = false return errs } func (r *PortRemap) Enable() error { if r.Enabled { return nil } err := r.ForceEnable() if err != nil { r.Disable() return err } return nil } func (nh *NetfilterHelper) PortRemap(name string, from, to uint16) *PortRemap { return &PortRemap{ IPTables: nh.IPTables, ChainName: name, From: from, To: to, } }