package io import ( "context" "encoding/binary" "errors" "fmt" "os/exec" "strconv" "strings" "github.com/coreos/go-iptables/iptables" "github.com/florianl/go-nfqueue" "github.com/mdlayher/netlink" ) const ( nfqueueNum = 100 nfqueueMaxPacketLen = 0xFFFF nfqueueDefaultQueueSize = 128 nfqueueConnMarkAccept = 1001 nfqueueConnMarkDrop = 1002 nftFamily = "inet" nftTable = "opengfw" ) var nftRulesForward = fmt.Sprintf(` define ACCEPT_CTMARK=%d define DROP_CTMARK=%d define QUEUE_NUM=%d table %s %s { chain FORWARD { type filter hook forward priority filter; policy accept; ct mark $ACCEPT_CTMARK counter accept ct mark $DROP_CTMARK counter drop counter queue num $QUEUE_NUM bypass } } `, nfqueueConnMarkAccept, nfqueueConnMarkDrop, nfqueueNum, nftFamily, nftTable) var nftRulesLocal = fmt.Sprintf(` define ACCEPT_CTMARK=%d define DROP_CTMARK=%d define QUEUE_NUM=%d table %s %s { chain INPUT { type filter hook input priority filter; policy accept; ct mark $ACCEPT_CTMARK counter accept ct mark $DROP_CTMARK counter drop counter queue num $QUEUE_NUM bypass } chain OUTPUT { type filter hook output priority filter; policy accept; ct mark $ACCEPT_CTMARK counter accept ct mark $DROP_CTMARK counter drop counter queue num $QUEUE_NUM bypass } } `, nfqueueConnMarkAccept, nfqueueConnMarkDrop, nfqueueNum, nftFamily, nftTable) var iptRulesForward = []iptRule{ {"filter", "FORWARD", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkAccept), "-j", "ACCEPT"}}, {"filter", "FORWARD", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkDrop), "-j", "DROP"}}, {"filter", "FORWARD", []string{"-j", "NFQUEUE", "--queue-num", strconv.Itoa(nfqueueNum), "--queue-bypass"}}, } var iptRulesLocal = []iptRule{ {"filter", "INPUT", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkAccept), "-j", "ACCEPT"}}, {"filter", "INPUT", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkDrop), "-j", "DROP"}}, {"filter", "INPUT", []string{"-j", "NFQUEUE", "--queue-num", strconv.Itoa(nfqueueNum), "--queue-bypass"}}, {"filter", "OUTPUT", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkAccept), "-j", "ACCEPT"}}, {"filter", "OUTPUT", []string{"-m", "connmark", "--mark", strconv.Itoa(nfqueueConnMarkDrop), "-j", "DROP"}}, {"filter", "OUTPUT", []string{"-j", "NFQUEUE", "--queue-num", strconv.Itoa(nfqueueNum), "--queue-bypass"}}, } var _ PacketIO = (*nfqueuePacketIO)(nil) var errNotNFQueuePacket = errors.New("not an NFQueue packet") type nfqueuePacketIO struct { n *nfqueue.Nfqueue local bool rSet bool // whether the nftables/iptables rules have been set // iptables not nil = use iptables instead of nftables ipt4 *iptables.IPTables ipt6 *iptables.IPTables } type NFQueuePacketIOConfig struct { QueueSize uint32 Local bool } func NewNFQueuePacketIO(config NFQueuePacketIOConfig) (PacketIO, error) { if config.QueueSize == 0 { config.QueueSize = nfqueueDefaultQueueSize } var ipt4, ipt6 *iptables.IPTables var err error if nftCheck() != nil { // We prefer nftables, but if it's not available, fall back to iptables ipt4, err = iptables.NewWithProtocol(iptables.ProtocolIPv4) if err != nil { return nil, err } ipt6, err = iptables.NewWithProtocol(iptables.ProtocolIPv6) if err != nil { return nil, err } } n, err := nfqueue.Open(&nfqueue.Config{ NfQueue: nfqueueNum, MaxPacketLen: nfqueueMaxPacketLen, MaxQueueLen: config.QueueSize, Copymode: nfqueue.NfQnlCopyPacket, Flags: nfqueue.NfQaCfgFlagConntrack, }) if err != nil { return nil, err } return &nfqueuePacketIO{ n: n, local: config.Local, ipt4: ipt4, ipt6: ipt6, }, nil } func (n *nfqueuePacketIO) Register(ctx context.Context, cb PacketCallback) error { err := n.n.RegisterWithErrorFunc(ctx, func(a nfqueue.Attribute) int { if a.PacketID == nil || a.Ct == nil || a.Payload == nil || len(*a.Payload) < 20 { // Invalid packet, ignore // 20 is the minimum possible size of an IP packet return 0 } p := &nfqueuePacket{ id: *a.PacketID, streamID: ctIDFromCtBytes(*a.Ct), data: *a.Payload, } return okBoolToInt(cb(p, nil)) }, func(e error) int { return okBoolToInt(cb(nil, e)) }) if err != nil { return err } if !n.rSet { if n.ipt4 != nil { err = n.setupIpt(n.local, false) } else { err = n.setupNft(n.local, false) } if err != nil { return err } n.rSet = true } return nil } func (n *nfqueuePacketIO) SetVerdict(p Packet, v Verdict, newPacket []byte) error { nP, ok := p.(*nfqueuePacket) if !ok { return &ErrInvalidPacket{Err: errNotNFQueuePacket} } switch v { case VerdictAccept: return n.n.SetVerdict(nP.id, nfqueue.NfAccept) case VerdictAcceptModify: return n.n.SetVerdictModPacket(nP.id, nfqueue.NfAccept, newPacket) case VerdictAcceptStream: return n.n.SetVerdictWithConnMark(nP.id, nfqueue.NfAccept, nfqueueConnMarkAccept) case VerdictDrop: return n.n.SetVerdict(nP.id, nfqueue.NfDrop) case VerdictDropStream: return n.n.SetVerdictWithConnMark(nP.id, nfqueue.NfDrop, nfqueueConnMarkDrop) default: // Invalid verdict, ignore for now return nil } } func (n *nfqueuePacketIO) Close() error { if n.rSet { if n.ipt4 != nil { _ = n.setupIpt(n.local, true) } else { _ = n.setupNft(n.local, true) } n.rSet = false } return n.n.Close() } func (n *nfqueuePacketIO) setupNft(local, remove bool) error { var rules string if local { rules = nftRulesLocal } else { rules = nftRulesForward } var err error if remove { err = nftDelete(nftFamily, nftTable) } else { // Delete first to make sure no leftover rules _ = nftDelete(nftFamily, nftTable) err = nftAdd(rules) } if err != nil { return err } return nil } func (n *nfqueuePacketIO) setupIpt(local, remove bool) error { var rules []iptRule if local { rules = iptRulesLocal } else { rules = iptRulesForward } var err error if remove { err = iptsBatchDeleteIfExists([]*iptables.IPTables{n.ipt4, n.ipt6}, rules) } else { err = iptsBatchAppendUnique([]*iptables.IPTables{n.ipt4, n.ipt6}, rules) } if err != nil { return err } return nil } var _ Packet = (*nfqueuePacket)(nil) type nfqueuePacket struct { id uint32 streamID uint32 data []byte } func (p *nfqueuePacket) StreamID() uint32 { return p.streamID } func (p *nfqueuePacket) Data() []byte { return p.data } func okBoolToInt(ok bool) int { if ok { return 0 } else { return 1 } } func nftCheck() error { _, err := exec.LookPath("nft") if err != nil { return err } return nil } func nftAdd(input string) error { cmd := exec.Command("nft", "-f", "-") cmd.Stdin = strings.NewReader(input) return cmd.Run() } func nftDelete(family, table string) error { cmd := exec.Command("nft", "delete", "table", family, table) return cmd.Run() } type iptRule struct { Table, Chain string RuleSpec []string } func iptsBatchAppendUnique(ipts []*iptables.IPTables, rules []iptRule) error { for _, r := range rules { for _, ipt := range ipts { err := ipt.AppendUnique(r.Table, r.Chain, r.RuleSpec...) if err != nil { return err } } } return nil } func iptsBatchDeleteIfExists(ipts []*iptables.IPTables, rules []iptRule) error { for _, r := range rules { for _, ipt := range ipts { err := ipt.DeleteIfExists(r.Table, r.Chain, r.RuleSpec...) if err != nil { return err } } } return nil } func ctIDFromCtBytes(ct []byte) uint32 { ctAttrs, err := netlink.UnmarshalAttributes(ct) if err != nil { return 0 } for _, attr := range ctAttrs { if attr.Type == 12 { // CTA_ID return binary.BigEndian.Uint32(attr.Data) } } return 0 }