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61 lines
1.7 KiB
Go
61 lines
1.7 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package monitor
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import (
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"fmt"
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"github.com/mdlayher/netlink"
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"golang.org/x/sys/unix"
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)
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const (
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RTMGRP_IPV4_IFADDR = 0x10
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RTMGRP_IPV4_ROUTE = 0x40
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)
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// nlConn wraps a *netlink.Conn and returns a monitor.Message
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// instead of a netlink.Message. Currently, messages are discarded,
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// but down the line, when messages trigger different logic depending
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// on the type of event, this provides the capability of handling
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// each architecture-specific message in a generic fashion.
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type nlConn struct {
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conn *netlink.Conn
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}
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func NewConn() (Conn, error) {
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conn, err := netlink.Dial(unix.NETLINK_ROUTE, &netlink.Config{
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// IPv4 address and route changes. Routes get us most of the
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// events of interest, but we need address as well to cover
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// things like DHCP deciding to give us a new address upon
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// renewal - routing wouldn't change, but all reachability
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// would.
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//
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// Why magic numbers? These aren't exposed in x/sys/unix
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// yet. The values come from rtnetlink.h, RTMGRP_IPV4_IFADDR
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// and RTMGRP_IPV4_ROUTE.
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Groups: RTMGRP_IPV4_IFADDR | RTMGRP_IPV4_ROUTE,
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})
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if err != nil {
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return nil, fmt.Errorf("dialing netlink socket: %v", err)
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}
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return &nlConn{conn}, nil
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}
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func (c *nlConn) Close() error {
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return c.conn.Close()
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}
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func (c *nlConn) Receive() (Message, error) {
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// currently ignoring the message
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_, err := c.conn.Receive()
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if err != nil {
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return nil, err
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}
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// TODO(]|[): this is where the NetLink-specific message would
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// get converted into a "standard" event message and returned.
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return nil, nil
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}
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