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client_linux.go
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client_linux.go
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//+build linux
package wifi
import (
"bytes"
"errors"
"net"
"os"
"time"
"unicode/utf8"
"github.com/mdlayher/genetlink"
"github.com/mdlayher/netlink"
"github.com/mdlayher/netlink/nlenc"
"github.com/mdlayher/wifi/internal/nl80211"
)
// Errors which may occur when interacting with generic netlink.
var (
errInvalidCommand = errors.New("invalid generic netlink response command")
errInvalidFamilyVersion = errors.New("invalid generic netlink response family version")
)
var _ osClient = &client{}
// A client is the Linux implementation of osClient, which makes use of
// netlink, generic netlink, and nl80211 to provide access to WiFi device
// actions and statistics.
type client struct {
c *genetlink.Conn
familyID uint16
familyVersion uint8
}
// newClient dials a generic netlink connection and verifies that nl80211
// is available for use by this package.
func newClient() (*client, error) {
c, err := genetlink.Dial(nil)
if err != nil {
return nil, err
}
return initClient(c)
}
func initClient(c *genetlink.Conn) (*client, error) {
family, err := c.GetFamily(nl80211.GenlName)
if err != nil {
// Ensure the genl socket is closed on error to avoid leaking file
// descriptors.
_ = c.Close()
return nil, err
}
return &client{
c: c,
familyID: family.ID,
familyVersion: family.Version,
}, nil
}
// Close closes the client's generic netlink connection.
func (c *client) Close() error {
return c.c.Close()
}
// Interfaces requests that nl80211 return a list of all WiFi interfaces present
// on this system.
func (c *client) Interfaces() ([]*Interface, error) {
// Ask nl80211 to dump a list of all WiFi interfaces
req := genetlink.Message{
Header: genetlink.Header{
Command: nl80211.CmdGetInterface,
Version: c.familyVersion,
},
}
flags := netlink.HeaderFlagsRequest | netlink.HeaderFlagsDump
msgs, err := c.c.Execute(req, c.familyID, flags)
if err != nil {
return nil, err
}
if err := c.checkMessages(msgs, nl80211.CmdNewInterface); err != nil {
return nil, err
}
return parseInterfaces(msgs)
}
// BSS requests that nl80211 return the BSS for the specified Interface.
func (c *client) BSS(ifi *Interface) (*BSS, error) {
b, err := netlink.MarshalAttributes(ifi.idAttrs())
if err != nil {
return nil, err
}
// Ask nl80211 to retrieve BSS information for the interface specified
// by its attributes
req := genetlink.Message{
Header: genetlink.Header{
Command: nl80211.CmdGetScan,
Version: c.familyVersion,
},
Data: b,
}
flags := netlink.HeaderFlagsRequest | netlink.HeaderFlagsDump
msgs, err := c.c.Execute(req, c.familyID, flags)
if err != nil {
return nil, err
}
if err := c.checkMessages(msgs, nl80211.CmdNewScanResults); err != nil {
return nil, err
}
return parseBSS(msgs)
}
// StationInfo requests that nl80211 return all station info for the specified
// Interface.
func (c *client) StationInfo(ifi *Interface) ([]*StationInfo, error) {
b, err := netlink.MarshalAttributes(ifi.idAttrs())
if err != nil {
return nil, err
}
// Ask nl80211 to retrieve station info for the interface specified
// by its attributes
req := genetlink.Message{
Header: genetlink.Header{
// From nl80211.h:
// * @NL80211_CMD_GET_STATION: Get station attributes for station identified by
// * %NL80211_ATTR_MAC on the interface identified by %NL80211_ATTR_IFINDEX.
Command: nl80211.CmdGetStation,
Version: c.familyVersion,
},
Data: b,
}
flags := netlink.HeaderFlagsRequest | netlink.HeaderFlagsDump
msgs, err := c.c.Execute(req, c.familyID, flags)
if err != nil {
return nil, err
}
if len(msgs) == 0 {
return nil, os.ErrNotExist
}
stations := make([]*StationInfo, len(msgs))
for i := range msgs {
if err := c.checkMessages(msgs, nl80211.CmdNewStation); err != nil {
return nil, err
}
if stations[i], err = parseStationInfo(msgs[i].Data); err != nil {
return nil, err
}
}
return stations, nil
}
// checkMessages verifies that response messages from generic netlink contain
// the command and family version we expect.
func (c *client) checkMessages(msgs []genetlink.Message, command uint8) error {
for _, m := range msgs {
if m.Header.Command != command {
return errInvalidCommand
}
if m.Header.Version != c.familyVersion {
return errInvalidFamilyVersion
}
}
return nil
}
// parseInterfaces parses zero or more Interfaces from nl80211 interface
// messages.
func parseInterfaces(msgs []genetlink.Message) ([]*Interface, error) {
ifis := make([]*Interface, 0, len(msgs))
for _, m := range msgs {
attrs, err := netlink.UnmarshalAttributes(m.Data)
if err != nil {
return nil, err
}
var ifi Interface
if err := (&ifi).parseAttributes(attrs); err != nil {
return nil, err
}
ifis = append(ifis, &ifi)
}
return ifis, nil
}
// idAttrs returns the netlink attributes required from an Interface to retrieve
// more data about it.
func (ifi *Interface) idAttrs() []netlink.Attribute {
return []netlink.Attribute{
{
Type: nl80211.AttrIfindex,
Data: nlenc.Uint32Bytes(uint32(ifi.Index)),
},
{
Type: nl80211.AttrMac,
Data: ifi.HardwareAddr,
},
}
}
// parseAttributes parses netlink attributes into an Interface's fields.
func (ifi *Interface) parseAttributes(attrs []netlink.Attribute) error {
for _, a := range attrs {
switch a.Type {
case nl80211.AttrIfindex:
ifi.Index = int(nlenc.Uint32(a.Data))
case nl80211.AttrIfname:
ifi.Name = nlenc.String(a.Data)
case nl80211.AttrMac:
ifi.HardwareAddr = net.HardwareAddr(a.Data)
case nl80211.AttrWiphy:
ifi.PHY = int(nlenc.Uint32(a.Data))
case nl80211.AttrIftype:
// NOTE: InterfaceType copies the ordering of nl80211's interface type
// constants. This may not be the case on other operating systems.
ifi.Type = InterfaceType(nlenc.Uint32(a.Data))
case nl80211.AttrWdev:
ifi.Device = int(nlenc.Uint64(a.Data))
case nl80211.AttrWiphyFreq:
ifi.Frequency = int(nlenc.Uint32(a.Data))
}
}
return nil
}
// parseBSS parses a single BSS with a status attribute from nl80211 BSS messages.
func parseBSS(msgs []genetlink.Message) (*BSS, error) {
for _, m := range msgs {
attrs, err := netlink.UnmarshalAttributes(m.Data)
if err != nil {
return nil, err
}
for _, a := range attrs {
if a.Type != nl80211.AttrBss {
continue
}
nattrs, err := netlink.UnmarshalAttributes(a.Data)
if err != nil {
return nil, err
}
// The BSS which is associated with an interface will have a status
// attribute
if !attrsContain(nattrs, nl80211.BssStatus) {
continue
}
var bss BSS
if err := (&bss).parseAttributes(nattrs); err != nil {
return nil, err
}
return &bss, nil
}
}
return nil, os.ErrNotExist
}
// parseAttributes parses netlink attributes into a BSS's fields.
func (b *BSS) parseAttributes(attrs []netlink.Attribute) error {
for _, a := range attrs {
switch a.Type {
case nl80211.BssBssid:
b.BSSID = net.HardwareAddr(a.Data)
case nl80211.BssFrequency:
b.Frequency = int(nlenc.Uint32(a.Data))
case nl80211.BssBeaconInterval:
// Raw value is in "Time Units (TU)". See:
// https://en.wikipedia.org/wiki/Beacon_frame
b.BeaconInterval = time.Duration(nlenc.Uint16(a.Data)) * 1024 * time.Microsecond
case nl80211.BssSeenMsAgo:
// * @NL80211_BSS_SEEN_MS_AGO: age of this BSS entry in ms
b.LastSeen = time.Duration(nlenc.Uint32(a.Data)) * time.Millisecond
case nl80211.BssStatus:
// NOTE: BSSStatus copies the ordering of nl80211's BSS status
// constants. This may not be the case on other operating systems.
b.Status = BSSStatus(nlenc.Uint32(a.Data))
case nl80211.BssInformationElements:
ies, err := parseIEs(a.Data)
if err != nil {
return err
}
// TODO(mdlayher): return more IEs if they end up being generally useful
for _, ie := range ies {
switch ie.ID {
case ieSSID:
b.SSID = decodeSSID(ie.Data)
}
}
}
}
return nil
}
// parseStationInfo parses StationInfo attributes from a byte slice of
// netlink attributes.
func parseStationInfo(b []byte) (*StationInfo, error) {
attrs, err := netlink.UnmarshalAttributes(b)
if err != nil {
return nil, err
}
var info StationInfo
for _, a := range attrs {
switch a.Type {
case nl80211.AttrMac:
info.HardwareAddr = net.HardwareAddr(a.Data)
case nl80211.AttrStaInfo:
nattrs, err := netlink.UnmarshalAttributes(a.Data)
if err != nil {
return nil, err
}
if err := (&info).parseAttributes(nattrs); err != nil {
return nil, err
}
// nl80211.AttrStaInfo is last attibute we are interested in
return &info, nil
default:
// The other attributes that are returned here appear
// nl80211.AttrIfindex, nl80211.AttrGeneration
// No need to parse them for now.
continue
}
}
// No station info found
return nil, os.ErrNotExist
}
// parseAttributes parses netlink attributes into a StationInfo's fields.
func (info *StationInfo) parseAttributes(attrs []netlink.Attribute) error {
for _, a := range attrs {
switch a.Type {
case nl80211.StaInfoConnectedTime:
// Though nl80211 does not specify, this value appears to be in seconds:
// * @NL80211_STA_INFO_CONNECTED_TIME: time since the station is last connected
info.Connected = time.Duration(nlenc.Uint32(a.Data)) * time.Second
case nl80211.StaInfoInactiveTime:
// * @NL80211_STA_INFO_INACTIVE_TIME: time since last activity (u32, msecs)
info.Inactive = time.Duration(nlenc.Uint32(a.Data)) * time.Millisecond
case nl80211.StaInfoRxBytes64:
info.ReceivedBytes = int(nlenc.Uint64(a.Data))
case nl80211.StaInfoTxBytes64:
info.TransmittedBytes = int(nlenc.Uint64(a.Data))
case nl80211.StaInfoSignal:
// * @NL80211_STA_INFO_SIGNAL: signal strength of last received PPDU (u8, dBm)
// Should just be cast to int8, see code here: https://git.kernel.org/pub/scm/linux/kernel/git/jberg/iw.git/tree/station.c#n378
info.Signal = int(int8(a.Data[0]))
case nl80211.StaInfoRxPackets:
info.ReceivedPackets = int(nlenc.Uint32(a.Data))
case nl80211.StaInfoTxPackets:
info.TransmittedPackets = int(nlenc.Uint32(a.Data))
case nl80211.StaInfoTxRetries:
info.TransmitRetries = int(nlenc.Uint32(a.Data))
case nl80211.StaInfoTxFailed:
info.TransmitFailed = int(nlenc.Uint32(a.Data))
case nl80211.StaInfoBeaconLoss:
info.BeaconLoss = int(nlenc.Uint32(a.Data))
case nl80211.StaInfoRxBitrate, nl80211.StaInfoTxBitrate:
rate, err := parseRateInfo(a.Data)
if err != nil {
return err
}
// TODO(mdlayher): return more statistics if they end up being
// generally useful
switch a.Type {
case nl80211.StaInfoRxBitrate:
info.ReceiveBitrate = rate.Bitrate
case nl80211.StaInfoTxBitrate:
info.TransmitBitrate = rate.Bitrate
}
}
// Only use 32-bit counters if the 64-bit counters are not present.
// If the 64-bit counters appear later in the slice, they will overwrite
// these values.
if info.ReceivedBytes == 0 && a.Type == nl80211.StaInfoRxBytes {
info.ReceivedBytes = int(nlenc.Uint32(a.Data))
}
if info.TransmittedBytes == 0 && a.Type == nl80211.StaInfoTxBytes {
info.TransmittedBytes = int(nlenc.Uint32(a.Data))
}
}
return nil
}
// rateInfo provides statistics about the receive or transmit rate of
// an interface.
type rateInfo struct {
// Bitrate in bits per second.
Bitrate int
}
// parseRateInfo parses a rateInfo from netlink attributes.
func parseRateInfo(b []byte) (*rateInfo, error) {
attrs, err := netlink.UnmarshalAttributes(b)
if err != nil {
return nil, err
}
var info rateInfo
for _, a := range attrs {
switch a.Type {
case nl80211.RateInfoBitrate32:
info.Bitrate = int(nlenc.Uint32(a.Data))
}
// Only use 16-bit counters if the 32-bit counters are not present.
// If the 32-bit counters appear later in the slice, they will overwrite
// these values.
if info.Bitrate == 0 && a.Type == nl80211.RateInfoBitrate {
info.Bitrate = int(nlenc.Uint16(a.Data))
}
}
// Scale bitrate to bits/second as base unit instead of 100kbits/second.
// * @NL80211_RATE_INFO_BITRATE: total bitrate (u16, 100kbit/s)
info.Bitrate *= 100 * 1000
return &info, nil
}
// attrsContain checks if a slice of netlink attributes contains an attribute
// with the specified type.
func attrsContain(attrs []netlink.Attribute, typ uint16) bool {
for _, a := range attrs {
if a.Type == typ {
return true
}
}
return false
}
// decodeSSID safely parses a byte slice into UTF-8 runes, and returns the
// resulting string from the runes.
func decodeSSID(b []byte) string {
buf := bytes.NewBuffer(nil)
for len(b) > 0 {
r, size := utf8.DecodeRune(b)
b = b[size:]
buf.WriteRune(r)
}
return buf.String()
}