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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package monitor
import (
"fmt"
"time"
"github.com/mdlayher/netlink"
"golang.org/x/sys/unix"
)
// nlConn wraps a *netlink.Conn and returns a monitor.Message
// instead of a netlink.Message. Currently, messages are discarded,
// but down the line, when messages trigger different logic depending
// on the type of event, this provides the capability of handling
// each architecture-specific message in a generic fashion.
type nlConn struct {
conn *netlink.Conn
}
func newOSMon() (osMon, error) {
conn, err := netlink.Dial(unix.NETLINK_ROUTE, &netlink.Config{
// IPv4 address and route changes. Routes get us most of the
// events of interest, but we need address as well to cover
// things like DHCP deciding to give us a new address upon
// renewal - routing wouldn't change, but all reachability
// would.
Groups: unix.RTMGRP_IPV4_IFADDR | unix.RTMGRP_IPV4_ROUTE,
})
if err != nil {
return nil, fmt.Errorf("dialing netlink socket: %v", err)
}
return &nlConn{conn}, nil
}
func (c *nlConn) Close() error {
c.conn.SetDeadline(time.Unix(0, 0)) // abort any Receive in flight
return c.conn.Close()
}
func (c *nlConn) Receive() (message, error) {
// currently ignoring the message
_, err := c.conn.Receive()
if err != nil {
return nil, err
}
// TODO(]|[): this is where the NetLink-specific message would
// get converted into a "standard" event message and returned.
return nil, nil
}
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