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// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
//go:build linux && !android
package linkspeed
import (
"github.com/mdlayher/genetlink"
"github.com/mdlayher/netlink"
"github.com/tailscale/wireguard-go/tun"
"golang.org/x/sys/unix"
"tailscale.com/net/tstun"
)
func init() {
tstun.HookSetLinkAttrs.Set(setLinkAttrs)
}
// setLinkSpeed sets the advertised link speed of the TUN interface.
func setLinkSpeed(iface tun.Device, mbps int) error {
name, err := iface.Name()
if err != nil {
return err
}
conn, err := genetlink.Dial(&netlink.Config{Strict: true})
if err != nil {
return err
}
defer conn.Close()
f, err := conn.GetFamily(unix.ETHTOOL_GENL_NAME)
if err != nil {
return err
}
ae := netlink.NewAttributeEncoder()
ae.Nested(unix.ETHTOOL_A_LINKMODES_HEADER, func(nae *netlink.AttributeEncoder) error {
nae.String(unix.ETHTOOL_A_HEADER_DEV_NAME, name)
return nil
})
ae.Uint32(unix.ETHTOOL_A_LINKMODES_SPEED, uint32(mbps))
b, err := ae.Encode()
if err != nil {
return err
}
_, err = conn.Execute(
genetlink.Message{
Header: genetlink.Header{
Command: unix.ETHTOOL_MSG_LINKMODES_SET,
Version: unix.ETHTOOL_GENL_VERSION,
},
Data: b,
},
f.ID,
netlink.Request|netlink.Acknowledge,
)
return err
}
// setLinkAttrs sets up link attributes that can be queried by external tools.
// Its failure is non-fatal to interface bringup.
func setLinkAttrs(iface tun.Device) error {
// By default the link speed is 10Mbps, which is easily exceeded and causes monitoring tools to complain (#3933).
return setLinkSpeed(iface, unix.SPEED_UNKNOWN)
}
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