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netlink/conntrack_linux.go

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package netlink
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"net"
"strings"
"time"
"github.com/vishvananda/netlink/nl"
"golang.org/x/sys/unix"
)
// ConntrackTableType Conntrack table for the netlink operation
type ConntrackTableType uint8
const (
// ConntrackTable Conntrack table
// https://github.com/torvalds/linux/blob/master/include/uapi/linux/netfilter/nfnetlink.h -> #define NFNL_SUBSYS_CTNETLINK 1
ConntrackTable = 1
// ConntrackExpectTable Conntrack expect table
// https://github.com/torvalds/linux/blob/master/include/uapi/linux/netfilter/nfnetlink.h -> #define NFNL_SUBSYS_CTNETLINK_EXP 2
ConntrackExpectTable = 2
)
const (
// backward compatibility with golang 1.6 which does not have io.SeekCurrent
seekCurrent = 1
)
// InetFamily Family type
type InetFamily uint8
// -L [table] [options] List conntrack or expectation table
// -G [table] parameters Get conntrack or expectation
// -I [table] parameters Create a conntrack or expectation
// -U [table] parameters Update a conntrack
// -E [table] [options] Show events
// -C [table] Show counter
// -S Show statistics
// ConntrackTableList returns the flow list of a table of a specific family
// conntrack -L [table] [options] List conntrack or expectation table
//
// If the returned error is [ErrDumpInterrupted], results may be inconsistent
// or incomplete.
func ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
return pkgHandle.ConntrackTableList(table, family)
}
// ConntrackTableFlush flushes all the flows of a specified table
// conntrack -F [table] Flush table
// The flush operation applies to all the family types
func ConntrackTableFlush(table ConntrackTableType) error {
return pkgHandle.ConntrackTableFlush(table)
}
// ConntrackCreate creates a new conntrack flow in the desired table
// conntrack -I [table] Create a conntrack or expectation
func ConntrackCreate(table ConntrackTableType, family InetFamily, flow *ConntrackFlow) error {
return pkgHandle.ConntrackCreate(table, family, flow)
}
// ConntrackUpdate updates an existing conntrack flow in the desired table using the handle
// conntrack -U [table] Update a conntrack
func ConntrackUpdate(table ConntrackTableType, family InetFamily, flow *ConntrackFlow) error {
return pkgHandle.ConntrackUpdate(table, family, flow)
}
// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter
// conntrack -D [table] parameters Delete conntrack or expectation
//
// Deprecated: use [ConntrackDeleteFilters] instead.
func ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter CustomConntrackFilter) (uint, error) {
return pkgHandle.ConntrackDeleteFilters(table, family, filter)
}
// ConntrackDeleteFilters deletes entries on the specified table matching any of the specified filters
// conntrack -D [table] parameters Delete conntrack or expectation
func ConntrackDeleteFilters(table ConntrackTableType, family InetFamily, filters ...CustomConntrackFilter) (uint, error) {
return pkgHandle.ConntrackDeleteFilters(table, family, filters...)
}
// ConntrackTableList returns the flow list of a table of a specific family using the netlink handle passed
// conntrack -L [table] [options] List conntrack or expectation table
//
// If the returned error is [ErrDumpInterrupted], results may be inconsistent
// or incomplete.
func (h *Handle) ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
res, executeErr := h.dumpConntrackTable(table, family)
if executeErr != nil && !errors.Is(executeErr, ErrDumpInterrupted) {
return nil, executeErr
}
// Deserialize all the flows
var result []*ConntrackFlow
for _, dataRaw := range res {
result = append(result, parseRawData(dataRaw))
}
return result, executeErr
}
// ConntrackTableFlush flushes all the flows of a specified table using the netlink handle passed
// conntrack -F [table] Flush table
// The flush operation applies to all the family types
func (h *Handle) ConntrackTableFlush(table ConntrackTableType) error {
req := h.newConntrackRequest(table, unix.AF_INET, nl.IPCTNL_MSG_CT_DELETE, unix.NLM_F_ACK)
_, err := req.Execute(unix.NETLINK_NETFILTER, 0)
return err
}
// ConntrackCreate creates a new conntrack flow in the desired table using the handle
// conntrack -I [table] Create a conntrack or expectation
func (h *Handle) ConntrackCreate(table ConntrackTableType, family InetFamily, flow *ConntrackFlow) error {
req := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_NEW, unix.NLM_F_ACK|unix.NLM_F_CREATE)
attr, err := flow.toNlData()
if err != nil {
return err
}
for _, a := range attr {
req.AddData(a)
}
_, err = req.Execute(unix.NETLINK_NETFILTER, 0)
return err
}
// ConntrackUpdate updates an existing conntrack flow in the desired table using the handle
// conntrack -U [table] Update a conntrack
func (h *Handle) ConntrackUpdate(table ConntrackTableType, family InetFamily, flow *ConntrackFlow) error {
req := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_NEW, unix.NLM_F_ACK|unix.NLM_F_REPLACE)
attr, err := flow.toNlData()
if err != nil {
return err
}
for _, a := range attr {
req.AddData(a)
}
_, err = req.Execute(unix.NETLINK_NETFILTER, 0)
return err
}
// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter using the netlink handle passed
// conntrack -D [table] parameters Delete conntrack or expectation
//
// Deprecated: use [Handle.ConntrackDeleteFilters] instead.
func (h *Handle) ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter CustomConntrackFilter) (uint, error) {
return h.ConntrackDeleteFilters(table, family, filter)
}
// ConntrackDeleteFilters deletes entries on the specified table matching any of the specified filters using the netlink handle passed
// conntrack -D [table] parameters Delete conntrack or expectation
func (h *Handle) ConntrackDeleteFilters(table ConntrackTableType, family InetFamily, filters ...CustomConntrackFilter) (uint, error) {
res, err := h.dumpConntrackTable(table, family)
if err != nil {
return 0, err
}
var matched uint
var errMsgs []string
for _, dataRaw := range res {
flow := parseRawData(dataRaw)
for _, filter := range filters {
if match := filter.MatchConntrackFlow(flow); match {
req2 := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_DELETE, unix.NLM_F_ACK)
// skip the first 4 byte that are the netfilter header, the newConntrackRequest is adding it already
req2.AddRawData(dataRaw[4:])
if _, err = req2.Execute(unix.NETLINK_NETFILTER, 0); err == nil {
matched++
// flow is already deleted, no need to match on other filters and continue to the next flow.
break
}
errMsgs = append(errMsgs, fmt.Sprintf("failed to delete conntrack flow '%s': %s", flow.String(), err.Error()))
}
}
}
if len(errMsgs) > 0 {
return matched, fmt.Errorf(strings.Join(errMsgs, "; "))
}
return matched, nil
}
func (h *Handle) newConntrackRequest(table ConntrackTableType, family InetFamily, operation, flags int) *nl.NetlinkRequest {
// Create the Netlink request object
req := h.newNetlinkRequest((int(table)<<8)|operation, flags)
// Add the netfilter header
msg := &nl.Nfgenmsg{
NfgenFamily: uint8(family),
Version: nl.NFNETLINK_V0,
ResId: 0,
}
req.AddData(msg)
return req
}
func (h *Handle) dumpConntrackTable(table ConntrackTableType, family InetFamily) ([][]byte, error) {
req := h.newConntrackRequest(table, family, nl.IPCTNL_MSG_CT_GET, unix.NLM_F_DUMP)
return req.Execute(unix.NETLINK_NETFILTER, 0)
}
// ProtoInfo wraps an L4-protocol structure - roughly corresponds to the
// __nfct_protoinfo union found in libnetfilter_conntrack/include/internal/object.h.
// Currently, only protocol names, and TCP state is supported.
type ProtoInfo interface {
Protocol() string
}
// ProtoInfoTCP corresponds to the `tcp` struct of the __nfct_protoinfo union.
// Only TCP state is currently supported.
type ProtoInfoTCP struct {
State uint8
}
// Protocol returns "tcp".
func (*ProtoInfoTCP) Protocol() string {return "tcp"}
func (p *ProtoInfoTCP) toNlData() ([]*nl.RtAttr, error) {
ctProtoInfo := nl.NewRtAttr(unix.NLA_F_NESTED | nl.CTA_PROTOINFO, []byte{})
ctProtoInfoTCP := nl.NewRtAttr(unix.NLA_F_NESTED|nl.CTA_PROTOINFO_TCP, []byte{})
ctProtoInfoTCPState := nl.NewRtAttr(nl.CTA_PROTOINFO_TCP_STATE, nl.Uint8Attr(p.State))
ctProtoInfoTCP.AddChild(ctProtoInfoTCPState)
ctProtoInfo.AddChild(ctProtoInfoTCP)
return []*nl.RtAttr{ctProtoInfo}, nil
}
// ProtoInfoSCTP only supports the protocol name.
type ProtoInfoSCTP struct {}
// Protocol returns "sctp".
func (*ProtoInfoSCTP) Protocol() string {return "sctp"}
// ProtoInfoDCCP only supports the protocol name.
type ProtoInfoDCCP struct {}
// Protocol returns "dccp".
func (*ProtoInfoDCCP) Protocol() string {return "dccp"}
// The full conntrack flow structure is very complicated and can be found in the file:
// http://git.netfilter.org/libnetfilter_conntrack/tree/include/internal/object.h
// For the time being, the structure below allows to parse and extract the base information of a flow
type IPTuple struct {
Bytes uint64
DstIP net.IP
DstPort uint16
Packets uint64
Protocol uint8
SrcIP net.IP
SrcPort uint16
}
// toNlData generates the inner fields of a nested tuple netlink datastructure
// does not generate the "nested"-flagged outer message.
func (t *IPTuple) toNlData(family uint8) ([]*nl.RtAttr, error) {
var srcIPsFlag, dstIPsFlag int
if family == nl.FAMILY_V4 {
srcIPsFlag = nl.CTA_IP_V4_SRC
dstIPsFlag = nl.CTA_IP_V4_DST
} else if family == nl.FAMILY_V6 {
srcIPsFlag = nl.CTA_IP_V6_SRC
dstIPsFlag = nl.CTA_IP_V6_DST
} else {
return []*nl.RtAttr{}, fmt.Errorf("couldn't generate netlink message for tuple due to unrecognized FamilyType '%d'", family)
}
ctTupleIP := nl.NewRtAttr(unix.NLA_F_NESTED|nl.CTA_TUPLE_IP, nil)
ctTupleIPSrc := nl.NewRtAttr(srcIPsFlag, t.SrcIP)
ctTupleIP.AddChild(ctTupleIPSrc)
ctTupleIPDst := nl.NewRtAttr(dstIPsFlag, t.DstIP)
ctTupleIP.AddChild(ctTupleIPDst)
ctTupleProto := nl.NewRtAttr(unix.NLA_F_NESTED|nl.CTA_TUPLE_PROTO, nil)
ctTupleProtoNum := nl.NewRtAttr(nl.CTA_PROTO_NUM, []byte{t.Protocol})
ctTupleProto.AddChild(ctTupleProtoNum)
ctTupleProtoSrcPort := nl.NewRtAttr(nl.CTA_PROTO_SRC_PORT, nl.BEUint16Attr(t.SrcPort))
ctTupleProto.AddChild(ctTupleProtoSrcPort)
ctTupleProtoDstPort := nl.NewRtAttr(nl.CTA_PROTO_DST_PORT, nl.BEUint16Attr(t.DstPort))
ctTupleProto.AddChild(ctTupleProtoDstPort, )
return []*nl.RtAttr{ctTupleIP, ctTupleProto}, nil
}
type ConntrackFlow struct {
FamilyType uint8
Forward IPTuple
Reverse IPTuple
Mark uint32
Zone uint16
TimeStart uint64
TimeStop uint64
TimeOut uint32
Labels []byte
ProtoInfo ProtoInfo
}
func (s *ConntrackFlow) String() string {
// conntrack cmd output:
// udp 17 src=127.0.0.1 dst=127.0.0.1 sport=4001 dport=1234 packets=5 bytes=532 [UNREPLIED] src=127.0.0.1 dst=127.0.0.1 sport=1234 dport=4001 packets=10 bytes=1078 mark=0 labels=0x00000000050012ac4202010000000000 zone=100
// start=2019-07-26 01:26:21.557800506 +0000 UTC stop=1970-01-01 00:00:00 +0000 UTC timeout=30(sec)
start := time.Unix(0, int64(s.TimeStart))
stop := time.Unix(0, int64(s.TimeStop))
timeout := int32(s.TimeOut)
res := fmt.Sprintf("%s\t%d src=%s dst=%s sport=%d dport=%d packets=%d bytes=%d\tsrc=%s dst=%s sport=%d dport=%d packets=%d bytes=%d mark=0x%x ",
nl.L4ProtoMap[s.Forward.Protocol], s.Forward.Protocol,
s.Forward.SrcIP.String(), s.Forward.DstIP.String(), s.Forward.SrcPort, s.Forward.DstPort, s.Forward.Packets, s.Forward.Bytes,
s.Reverse.SrcIP.String(), s.Reverse.DstIP.String(), s.Reverse.SrcPort, s.Reverse.DstPort, s.Reverse.Packets, s.Reverse.Bytes,
s.Mark)
if len(s.Labels) > 0 {
res += fmt.Sprintf("labels=0x%x ", s.Labels)
}
if s.Zone != 0 {
res += fmt.Sprintf("zone=%d ", s.Zone)
}
res += fmt.Sprintf("start=%v stop=%v timeout=%d(sec)", start, stop, timeout)
return res
}
// toNlData generates netlink messages representing the flow.
func (s *ConntrackFlow) toNlData() ([]*nl.RtAttr, error) {
var payload []*nl.RtAttr
// The message structure is built as follows:
// <len, NLA_F_NESTED|CTA_TUPLE_ORIG>
// <len, NLA_F_NESTED|CTA_TUPLE_IP>
// <len, [CTA_IP_V4_SRC|CTA_IP_V6_SRC]>
// <IP>
// <len, [CTA_IP_V4_DST|CTA_IP_V6_DST]>
// <IP>
// <len, NLA_F_NESTED|nl.CTA_TUPLE_PROTO>
// <len, CTA_PROTO_NUM>
// <uint8>
// <len, CTA_PROTO_SRC_PORT>
// <BEuint16>
// <len, CTA_PROTO_DST_PORT>
// <BEuint16>
// <len, NLA_F_NESTED|CTA_TUPLE_REPLY>
// <len, NLA_F_NESTED|CTA_TUPLE_IP>
// <len, [CTA_IP_V4_SRC|CTA_IP_V6_SRC]>
// <IP>
// <len, [CTA_IP_V4_DST|CTA_IP_V6_DST]>
// <IP>
// <len, NLA_F_NESTED|nl.CTA_TUPLE_PROTO>
// <len, CTA_PROTO_NUM>
// <uint8>
// <len, CTA_PROTO_SRC_PORT>
// <BEuint16>
// <len, CTA_PROTO_DST_PORT>
// <BEuint16>
// <len, CTA_STATUS>
// <uint64>
// <len, CTA_MARK>
// <BEuint64>
// <len, CTA_TIMEOUT>
// <BEuint64>
// <len, NLA_F_NESTED|CTA_PROTOINFO>
// CTA_TUPLE_ORIG
ctTupleOrig := nl.NewRtAttr(unix.NLA_F_NESTED|nl.CTA_TUPLE_ORIG, nil)
forwardFlowAttrs, err := s.Forward.toNlData(s.FamilyType)
if err != nil {
return nil, fmt.Errorf("couldn't generate netlink data for conntrack forward flow: %w", err)
}
for _, a := range forwardFlowAttrs {
ctTupleOrig.AddChild(a)
}
// CTA_TUPLE_REPLY
ctTupleReply := nl.NewRtAttr(unix.NLA_F_NESTED|nl.CTA_TUPLE_REPLY, nil)
reverseFlowAttrs, err := s.Reverse.toNlData(s.FamilyType)
if err != nil {
return nil, fmt.Errorf("couldn't generate netlink data for conntrack reverse flow: %w", err)
}
for _, a := range reverseFlowAttrs {
ctTupleReply.AddChild(a)
}
ctMark := nl.NewRtAttr(nl.CTA_MARK, nl.BEUint32Attr(s.Mark))
ctTimeout := nl.NewRtAttr(nl.CTA_TIMEOUT, nl.BEUint32Attr(s.TimeOut))
payload = append(payload, ctTupleOrig, ctTupleReply, ctMark, ctTimeout)
if s.ProtoInfo != nil {
switch p := s.ProtoInfo.(type) {
case *ProtoInfoTCP:
attrs, err := p.toNlData()
if err != nil {
return nil, fmt.Errorf("couldn't generate netlink data for conntrack flow's TCP protoinfo: %w", err)
}
payload = append(payload, attrs...)
default:
return nil, errors.New("couldn't generate netlink data for conntrack: field 'ProtoInfo' only supports TCP or nil")
}
}
return payload, nil
}
// This method parse the ip tuple structure
// The message structure is the following:
// <len, [CTA_IP_V4_SRC|CTA_IP_V6_SRC], 16 bytes for the IP>
// <len, [CTA_IP_V4_DST|CTA_IP_V6_DST], 16 bytes for the IP>
// <len, NLA_F_NESTED|nl.CTA_TUPLE_PROTO, 1 byte for the protocol, 3 bytes of padding>
// <len, CTA_PROTO_SRC_PORT, 2 bytes for the source port, 2 bytes of padding>
// <len, CTA_PROTO_DST_PORT, 2 bytes for the source port, 2 bytes of padding>
func parseIpTuple(reader *bytes.Reader, tpl *IPTuple) uint8 {
for i := 0; i < 2; i++ {
_, t, _, v := parseNfAttrTLV(reader)
switch t {
case nl.CTA_IP_V4_SRC, nl.CTA_IP_V6_SRC:
tpl.SrcIP = v
case nl.CTA_IP_V4_DST, nl.CTA_IP_V6_DST:
tpl.DstIP = v
}
}
// Get total length of nested protocol-specific info.
_, _, protoInfoTotalLen := parseNfAttrTL(reader)
_, t, l, v := parseNfAttrTLV(reader)
// Track the number of bytes read.
protoInfoBytesRead := uint16(nl.SizeofNfattr) + l
if t == nl.CTA_PROTO_NUM {
tpl.Protocol = uint8(v[0])
}
// We only parse TCP & UDP headers. Skip the others.
if tpl.Protocol != unix.IPPROTO_TCP && tpl.Protocol != unix.IPPROTO_UDP {
// skip the rest
bytesRemaining := protoInfoTotalLen - protoInfoBytesRead
reader.Seek(int64(bytesRemaining), seekCurrent)
return tpl.Protocol
}
// Skip 3 bytes of padding
reader.Seek(3, seekCurrent)
protoInfoBytesRead += 3
for i := 0; i < 2; i++ {
_, t, _ := parseNfAttrTL(reader)
protoInfoBytesRead += uint16(nl.SizeofNfattr)
switch t {
case nl.CTA_PROTO_SRC_PORT:
parseBERaw16(reader, &tpl.SrcPort)
protoInfoBytesRead += 2
case nl.CTA_PROTO_DST_PORT:
parseBERaw16(reader, &tpl.DstPort)
protoInfoBytesRead += 2
}
// Skip 2 bytes of padding
reader.Seek(2, seekCurrent)
protoInfoBytesRead += 2
}
// Skip any remaining/unknown parts of the message
bytesRemaining := protoInfoTotalLen - protoInfoBytesRead
reader.Seek(int64(bytesRemaining), seekCurrent)
return tpl.Protocol
}
func parseNfAttrTLV(r *bytes.Reader) (isNested bool, attrType, len uint16, value []byte) {
isNested, attrType, len = parseNfAttrTL(r)
value = make([]byte, len)
binary.Read(r, binary.BigEndian, &value)
return isNested, attrType, len, value
}
func parseNfAttrTL(r *bytes.Reader) (isNested bool, attrType, len uint16) {
binary.Read(r, nl.NativeEndian(), &len)
len -= nl.SizeofNfattr
binary.Read(r, nl.NativeEndian(), &attrType)
isNested = (attrType & nl.NLA_F_NESTED) == nl.NLA_F_NESTED
attrType = attrType & (nl.NLA_F_NESTED - 1)
return isNested, attrType, len
}
// skipNfAttrValue seeks `r` past attr of length `len`.
// Maintains buffer alignment.
// Returns length of the seek performed.
func skipNfAttrValue(r *bytes.Reader, len uint16) uint16 {
len = (len + nl.NLA_ALIGNTO - 1) & ^(nl.NLA_ALIGNTO - 1)
r.Seek(int64(len), seekCurrent)
return len
}
func parseBERaw16(r *bytes.Reader, v *uint16) {
binary.Read(r, binary.BigEndian, v)
}
func parseBERaw32(r *bytes.Reader, v *uint32) {
binary.Read(r, binary.BigEndian, v)
}
func parseBERaw64(r *bytes.Reader, v *uint64) {
binary.Read(r, binary.BigEndian, v)
}
func parseRaw32(r *bytes.Reader, v *uint32) {
binary.Read(r, nl.NativeEndian(), v)
}
func parseByteAndPacketCounters(r *bytes.Reader) (bytes, packets uint64) {
for i := 0; i < 2; i++ {
switch _, t, _ := parseNfAttrTL(r); t {
case nl.CTA_COUNTERS_BYTES:
parseBERaw64(r, &bytes)
case nl.CTA_COUNTERS_PACKETS:
parseBERaw64(r, &packets)
default:
return
}
}
return
}
// when the flow is alive, only the timestamp_start is returned in structure
func parseTimeStamp(r *bytes.Reader, readSize uint16) (tstart, tstop uint64) {
var numTimeStamps int
oneItem := nl.SizeofNfattr + 8 // 4 bytes attr header + 8 bytes timestamp
if readSize == uint16(oneItem) {
numTimeStamps = 1
} else if readSize == 2*uint16(oneItem) {
numTimeStamps = 2
} else {
return
}
for i := 0; i < numTimeStamps; i++ {
switch _, t, _ := parseNfAttrTL(r); t {
case nl.CTA_TIMESTAMP_START:
parseBERaw64(r, &tstart)
case nl.CTA_TIMESTAMP_STOP:
parseBERaw64(r, &tstop)
default:
return
}
}
return
}
func parseProtoInfoTCPState(r *bytes.Reader) (s uint8) {
binary.Read(r, binary.BigEndian, &s)
r.Seek(nl.SizeofNfattr - 1, seekCurrent)
return s
}
// parseProtoInfoTCP reads the entire nested protoinfo structure, but only parses the state attr.
func parseProtoInfoTCP(r *bytes.Reader, attrLen uint16) (*ProtoInfoTCP) {
p := new(ProtoInfoTCP)
bytesRead := 0
for bytesRead < int(attrLen) {
_, t, l := parseNfAttrTL(r)
bytesRead += nl.SizeofNfattr
switch t {
case nl.CTA_PROTOINFO_TCP_STATE:
p.State = parseProtoInfoTCPState(r)
bytesRead += nl.SizeofNfattr
default:
bytesRead += int(skipNfAttrValue(r, l))
}
}
return p
}
func parseProtoInfo(r *bytes.Reader, attrLen uint16) (p ProtoInfo) {
bytesRead := 0
for bytesRead < int(attrLen) {
_, t, l := parseNfAttrTL(r)
bytesRead += nl.SizeofNfattr
switch t {
case nl.CTA_PROTOINFO_TCP:
p = parseProtoInfoTCP(r, l)
bytesRead += int(l)
// No inner fields of DCCP / SCTP currently supported.
case nl.CTA_PROTOINFO_DCCP:
p = new(ProtoInfoDCCP)
skipped := skipNfAttrValue(r, l)
bytesRead += int(skipped)
case nl.CTA_PROTOINFO_SCTP:
p = new(ProtoInfoSCTP)
skipped := skipNfAttrValue(r, l)
bytesRead += int(skipped)
default:
skipped := skipNfAttrValue(r, l)
bytesRead += int(skipped)
}
}
return p
}
func parseTimeOut(r *bytes.Reader) (ttimeout uint32) {
parseBERaw32(r, &ttimeout)
return
}
func parseConnectionMark(r *bytes.Reader) (mark uint32) {
parseBERaw32(r, &mark)
return
}
func parseConnectionLabels(r *bytes.Reader) (label []byte) {
label = make([]byte, 16) // netfilter defines 128 bit labels value
binary.Read(r, nl.NativeEndian(), &label)
return
}
func parseConnectionZone(r *bytes.Reader) (zone uint16) {
parseBERaw16(r, &zone)
r.Seek(2, seekCurrent)
return
}
func parseRawData(data []byte) *ConntrackFlow {
s := &ConntrackFlow{}
// First there is the Nfgenmsg header
// consume only the family field
reader := bytes.NewReader(data)
binary.Read(reader, nl.NativeEndian(), &s.FamilyType)
// skip rest of the Netfilter header
reader.Seek(3, seekCurrent)
// The message structure is the following:
// <len, NLA_F_NESTED|CTA_TUPLE_ORIG> 4 bytes
// <len, NLA_F_NESTED|CTA_TUPLE_IP> 4 bytes
// flow information of the forward flow
// <len, NLA_F_NESTED|CTA_TUPLE_REPLY> 4 bytes
// <len, NLA_F_NESTED|CTA_TUPLE_IP> 4 bytes
// flow information of the reverse flow
for reader.Len() > 0 {
if nested, t, l := parseNfAttrTL(reader); nested {
switch t {
case nl.CTA_TUPLE_ORIG:
if nested, t, l = parseNfAttrTL(reader); nested && t == nl.CTA_TUPLE_IP {
parseIpTuple(reader, &s.Forward)
}
case nl.CTA_TUPLE_REPLY:
if nested, t, l = parseNfAttrTL(reader); nested && t == nl.CTA_TUPLE_IP {
parseIpTuple(reader, &s.Reverse)
} else {
// Header not recognized skip it
skipNfAttrValue(reader, l)
}
case nl.CTA_COUNTERS_ORIG:
s.Forward.Bytes, s.Forward.Packets = parseByteAndPacketCounters(reader)
case nl.CTA_COUNTERS_REPLY:
s.Reverse.Bytes, s.Reverse.Packets = parseByteAndPacketCounters(reader)
case nl.CTA_TIMESTAMP:
s.TimeStart, s.TimeStop = parseTimeStamp(reader, l)
case nl.CTA_PROTOINFO:
s.ProtoInfo = parseProtoInfo(reader, l)
default:
skipNfAttrValue(reader, l)
}
} else {
switch t {
case nl.CTA_MARK:
s.Mark = parseConnectionMark(reader)
case nl.CTA_LABELS:
s.Labels = parseConnectionLabels(reader)
case nl.CTA_TIMEOUT:
s.TimeOut = parseTimeOut(reader)
case nl.CTA_ID, nl.CTA_STATUS, nl.CTA_USE:
skipNfAttrValue(reader, l)
case nl.CTA_ZONE:
s.Zone = parseConnectionZone(reader)
default:
skipNfAttrValue(reader, l)
}
}
}
return s
}
// Conntrack parameters and options:
// -n, --src-nat ip source NAT ip
// -g, --dst-nat ip destination NAT ip
// -j, --any-nat ip source or destination NAT ip
// -m, --mark mark Set mark
// -c, --secmark secmark Set selinux secmark
// -e, --event-mask eventmask Event mask, eg. NEW,DESTROY
// -z, --zero Zero counters while listing
// -o, --output type[,...] Output format, eg. xml
// -l, --label label[,...] conntrack labels
// Common parameters and options:
// -s, --src, --orig-src ip Source address from original direction
// -d, --dst, --orig-dst ip Destination address from original direction
// -r, --reply-src ip Source address from reply direction
// -q, --reply-dst ip Destination address from reply direction
// -p, --protonum proto Layer 4 Protocol, eg. 'tcp'
// -f, --family proto Layer 3 Protocol, eg. 'ipv6'
// -t, --timeout timeout Set timeout
// -u, --status status Set status, eg. ASSURED
// -w, --zone value Set conntrack zone
// --orig-zone value Set zone for original direction
// --reply-zone value Set zone for reply direction
// -b, --buffer-size Netlink socket buffer size
// --mask-src ip Source mask address
// --mask-dst ip Destination mask address
// Layer 4 Protocol common parameters and options:
// TCP, UDP, SCTP, UDPLite and DCCP
// --sport, --orig-port-src port Source port in original direction
// --dport, --orig-port-dst port Destination port in original direction
// Filter types
type ConntrackFilterType uint8
const (
ConntrackOrigSrcIP = iota // -orig-src ip Source address from original direction
ConntrackOrigDstIP // -orig-dst ip Destination address from original direction
ConntrackReplySrcIP // --reply-src ip Reply Source IP
ConntrackReplyDstIP // --reply-dst ip Reply Destination IP
ConntrackReplyAnyIP // Match source or destination reply IP
ConntrackOrigSrcPort // --orig-port-src port Source port in original direction
ConntrackOrigDstPort // --orig-port-dst port Destination port in original direction
ConntrackMatchLabels // --label label1,label2 Labels used in entry
ConntrackUnmatchLabels // --label label1,label2 Labels not used in entry
ConntrackNatSrcIP = ConntrackReplySrcIP // deprecated use instead ConntrackReplySrcIP
ConntrackNatDstIP = ConntrackReplyDstIP // deprecated use instead ConntrackReplyDstIP
ConntrackNatAnyIP = ConntrackReplyAnyIP // deprecated use instead ConntrackReplyAnyIP
)
type CustomConntrackFilter interface {
// MatchConntrackFlow applies the filter to the flow and returns true if the flow matches
// the filter or false otherwise
MatchConntrackFlow(flow *ConntrackFlow) bool
}
type ConntrackFilter struct {
ipNetFilter map[ConntrackFilterType]*net.IPNet
portFilter map[ConntrackFilterType]uint16
protoFilter uint8
labelFilter map[ConntrackFilterType][][]byte
zoneFilter *uint16
}
// AddIPNet adds a IP subnet to the conntrack filter
func (f *ConntrackFilter) AddIPNet(tp ConntrackFilterType, ipNet *net.IPNet) error {
if ipNet == nil {
return fmt.Errorf("Filter attribute empty")
}
if f.ipNetFilter == nil {
f.ipNetFilter = make(map[ConntrackFilterType]*net.IPNet)
}
if _, ok := f.ipNetFilter[tp]; ok {
return errors.New("Filter attribute already present")
}
f.ipNetFilter[tp] = ipNet
return nil
}
// AddIP adds an IP to the conntrack filter
func (f *ConntrackFilter) AddIP(tp ConntrackFilterType, ip net.IP) error {
if ip == nil {
return fmt.Errorf("Filter attribute empty")
}
return f.AddIPNet(tp, NewIPNet(ip))
}
// AddPort adds a Port to the conntrack filter if the Layer 4 protocol allows it
func (f *ConntrackFilter) AddPort(tp ConntrackFilterType, port uint16) error {
switch f.protoFilter {
// TCP, UDP, DCCP, SCTP, UDPLite
case 6, 17, 33, 132, 136:
default:
return fmt.Errorf("Filter attribute not available without a valid Layer 4 protocol: %d", f.protoFilter)
}
if f.portFilter == nil {
f.portFilter = make(map[ConntrackFilterType]uint16)
}
if _, ok := f.portFilter[tp]; ok {
return errors.New("Filter attribute already present")
}
f.portFilter[tp] = port
return nil
}
// AddProtocol adds the Layer 4 protocol to the conntrack filter
func (f *ConntrackFilter) AddProtocol(proto uint8) error {
if f.protoFilter != 0 {
return errors.New("Filter attribute already present")
}
f.protoFilter = proto
return nil
}
// AddLabels adds the provided list (zero or more) of labels to the conntrack filter
// ConntrackFilterType here can be either:
// 1. ConntrackMatchLabels: This matches every flow that has a label value (len(flow.Labels) > 0)
// against the list of provided labels. If `flow.Labels` contains ALL the provided labels
// it is considered a match. This can be used when you want to match flows that contain
// one or more labels.
// 2. ConntrackUnmatchLabels: This matches every flow that has a label value (len(flow.Labels) > 0)
// against the list of provided labels. If `flow.Labels` does NOT contain ALL the provided labels
// it is considered a match. This can be used when you want to match flows that don't contain
// one or more labels.
func (f *ConntrackFilter) AddLabels(tp ConntrackFilterType, labels [][]byte) error {
if len(labels) == 0 {
return errors.New("Invalid length for provided labels")
}
if f.labelFilter == nil {
f.labelFilter = make(map[ConntrackFilterType][][]byte)
}
if _, ok := f.labelFilter[tp]; ok {
return errors.New("Filter attribute already present")
}
f.labelFilter[tp] = labels
return nil
}
// AddZone adds a zone to the conntrack filter
func (f *ConntrackFilter) AddZone(zone uint16) error {
if f.zoneFilter != nil {
return errors.New("Filter attribute already present")
}
f.zoneFilter = &zone
return nil
}
// MatchConntrackFlow applies the filter to the flow and returns true if the flow matches the filter
// false otherwise
func (f *ConntrackFilter) MatchConntrackFlow(flow *ConntrackFlow) bool {
if len(f.ipNetFilter) == 0 && len(f.portFilter) == 0 && f.protoFilter == 0 && len(f.labelFilter) == 0 && f.zoneFilter == nil {
// empty filter always not match
return false
}
// -p, --protonum proto Layer 4 Protocol, eg. 'tcp'
if f.protoFilter != 0 && flow.Forward.Protocol != f.protoFilter {
// different Layer 4 protocol always not match
return false
}
// Conntrack zone filter
if f.zoneFilter != nil && *f.zoneFilter != flow.Zone {
return false
}
match := true
// IP conntrack filter
if len(f.ipNetFilter) > 0 {
// -orig-src ip Source address from original direction
if elem, found := f.ipNetFilter[ConntrackOrigSrcIP]; found {
match = match && elem.Contains(flow.Forward.SrcIP)
}
// -orig-dst ip Destination address from original direction
if elem, found := f.ipNetFilter[ConntrackOrigDstIP]; match && found {
match = match && elem.Contains(flow.Forward.DstIP)
}
// -src-nat ip Source NAT ip
if elem, found := f.ipNetFilter[ConntrackReplySrcIP]; match && found {
match = match && elem.Contains(flow.Reverse.SrcIP)
}
// -dst-nat ip Destination NAT ip
if elem, found := f.ipNetFilter[ConntrackReplyDstIP]; match && found {
match = match && elem.Contains(flow.Reverse.DstIP)
}
// Match source or destination reply IP
if elem, found := f.ipNetFilter[ConntrackReplyAnyIP]; match && found {
match = match && (elem.Contains(flow.Reverse.SrcIP) || elem.Contains(flow.Reverse.DstIP))
}
}
// Layer 4 Port filter
if len(f.portFilter) > 0 {
// -orig-port-src port Source port from original direction
if elem, found := f.portFilter[ConntrackOrigSrcPort]; match && found {
match = match && elem == flow.Forward.SrcPort
}
// -orig-port-dst port Destination port from original direction
if elem, found := f.portFilter[ConntrackOrigDstPort]; match && found {
match = match && elem == flow.Forward.DstPort
}
}
// Label filter
if len(f.labelFilter) > 0 {
if len(flow.Labels) > 0 {
// --label label1,label2 in conn entry;
// every label passed should be contained in flow.Labels for a match to be true
if elem, found := f.labelFilter[ConntrackMatchLabels]; match && found {
for _, label := range elem {
match = match && (bytes.Contains(flow.Labels, label))
}
}
// --label label1,label2 in conn entry;
// every label passed should be not contained in flow.Labels for a match to be true
if elem, found := f.labelFilter[ConntrackUnmatchLabels]; match && found {
for _, label := range elem {
match = match && !(bytes.Contains(flow.Labels, label))
}
}
} else {
// flow doesn't contain labels, so it doesn't contain or notContain any provided matches
match = false
}
}
return match
}
var _ CustomConntrackFilter = (*ConntrackFilter)(nil)
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