151 lines
3.3 KiB
Go
151 lines
3.3 KiB
Go
//go:build linux
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// +build linux
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package genetlink
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import (
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"errors"
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"fmt"
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"math"
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"github.com/mdlayher/netlink"
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"github.com/mdlayher/netlink/nlenc"
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"golang.org/x/sys/unix"
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)
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// errInvalidFamilyVersion is returned when a family's version is greater
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// than an 8-bit integer.
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var errInvalidFamilyVersion = errors.New("invalid family version attribute")
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// getFamily retrieves a generic netlink family with the specified name.
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func (c *Conn) getFamily(name string) (Family, error) {
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b, err := netlink.MarshalAttributes([]netlink.Attribute{{
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Type: unix.CTRL_ATTR_FAMILY_NAME,
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Data: nlenc.Bytes(name),
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}})
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if err != nil {
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return Family{}, err
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}
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req := Message{
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Header: Header{
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Command: unix.CTRL_CMD_GETFAMILY,
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// TODO(mdlayher): grab nlctrl version?
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Version: 1,
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},
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Data: b,
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}
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msgs, err := c.Execute(req, unix.GENL_ID_CTRL, netlink.Request)
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if err != nil {
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return Family{}, err
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}
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// TODO(mdlayher): consider interpreting generic netlink header values
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families, err := buildFamilies(msgs)
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if err != nil {
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return Family{}, err
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}
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if len(families) != 1 {
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// If this were to ever happen, netlink must be in a state where
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// its answers cannot be trusted
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panic(fmt.Sprintf("netlink returned multiple families for name: %q", name))
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}
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return families[0], nil
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}
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// listFamilies retrieves all registered generic netlink families.
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func (c *Conn) listFamilies() ([]Family, error) {
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req := Message{
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Header: Header{
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Command: unix.CTRL_CMD_GETFAMILY,
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// TODO(mdlayher): grab nlctrl version?
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Version: 1,
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},
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}
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msgs, err := c.Execute(req, unix.GENL_ID_CTRL, netlink.Request|netlink.Dump)
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if err != nil {
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return nil, err
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}
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return buildFamilies(msgs)
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}
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// buildFamilies builds a slice of Families by parsing attributes from the
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// input Messages.
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func buildFamilies(msgs []Message) ([]Family, error) {
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families := make([]Family, 0, len(msgs))
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for _, m := range msgs {
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f, err := parseFamily(m.Data)
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if err != nil {
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return nil, err
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}
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families = append(families, f)
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}
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return families, nil
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}
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// parseFamily decodes netlink attributes into a Family.
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func parseFamily(b []byte) (Family, error) {
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ad, err := netlink.NewAttributeDecoder(b)
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if err != nil {
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return Family{}, err
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}
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var f Family
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for ad.Next() {
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switch ad.Type() {
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case unix.CTRL_ATTR_FAMILY_ID:
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f.ID = ad.Uint16()
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case unix.CTRL_ATTR_FAMILY_NAME:
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f.Name = ad.String()
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case unix.CTRL_ATTR_VERSION:
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v := ad.Uint32()
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if v > math.MaxUint8 {
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return Family{}, errInvalidFamilyVersion
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}
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f.Version = uint8(v)
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case unix.CTRL_ATTR_MCAST_GROUPS:
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ad.Nested(parseMulticastGroups(&f.Groups))
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}
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}
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if err := ad.Err(); err != nil {
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return Family{}, err
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}
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return f, nil
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}
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// parseMulticastGroups parses an array of multicast group nested attributes
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// into a slice of MulticastGroups.
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func parseMulticastGroups(groups *[]MulticastGroup) func(*netlink.AttributeDecoder) error {
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return func(ad *netlink.AttributeDecoder) error {
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*groups = make([]MulticastGroup, 0, ad.Len())
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for ad.Next() {
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ad.Nested(func(nad *netlink.AttributeDecoder) error {
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var g MulticastGroup
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for nad.Next() {
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switch nad.Type() {
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case unix.CTRL_ATTR_MCAST_GRP_NAME:
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g.Name = nad.String()
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case unix.CTRL_ATTR_MCAST_GRP_ID:
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g.ID = nad.Uint32()
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}
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}
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*groups = append(*groups, g)
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return nil
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})
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}
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return nil
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}
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}
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