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4b75a27969
Fixes #532
125 lines
3.5 KiB
Go
125 lines
3.5 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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// +build !android
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package monitor
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import (
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"fmt"
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"net"
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"time"
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"github.com/jsimonetti/rtnetlink"
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"github.com/mdlayher/netlink"
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"golang.org/x/sys/unix"
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"inet.af/netaddr"
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"tailscale.com/net/tsaddr"
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"tailscale.com/types/logger"
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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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logf logger.Logf
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conn *netlink.Conn
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buffered []netlink.Message
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}
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func newOSMon(logf logger.Logf) (osMon, 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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Groups: unix.RTMGRP_IPV4_IFADDR | unix.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{logf: logf, conn: conn}, nil
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}
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func (c *nlConn) Close() error {
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c.conn.SetDeadline(time.Unix(0, 0)) // abort any Receive in flight
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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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if len(c.buffered) == 0 {
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var err error
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c.buffered, 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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if len(c.buffered) == 0 {
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// Unexpected. Not seen in wild, but sleep defensively.
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time.Sleep(time.Second)
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return nil, nil
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}
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}
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msg := c.buffered[0]
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c.buffered = c.buffered[1:]
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// See https://github.com/torvalds/linux/blob/master/include/uapi/linux/rtnetlink.h
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// And https://man7.org/linux/man-pages/man7/rtnetlink.7.html
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switch msg.Header.Type {
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case unix.RTM_NEWADDR:
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var rmsg rtnetlink.AddressMessage
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if err := rmsg.UnmarshalBinary(msg.Data); err != nil {
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c.logf("RTM_NEWADDR: failed to parse: %v", err)
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return nil, nil
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}
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return &newAddrMessage{
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Label: rmsg.Attributes.Label,
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Addr: netaddrIP(rmsg.Attributes.Local),
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}, nil
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case unix.RTM_NEWROUTE:
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var rmsg rtnetlink.RouteMessage
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if err := rmsg.UnmarshalBinary(msg.Data); err != nil {
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c.logf("RTM_NEWROUTE: failed to parse: %v", err)
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return nil, nil
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}
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return &newRouteMessage{
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Table: rmsg.Table,
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Src: netaddrIP(rmsg.Attributes.Src),
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Dst: netaddrIP(rmsg.Attributes.Dst),
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Gateway: netaddrIP(rmsg.Attributes.Gateway),
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}, nil
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default:
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// TODO(bradfitz): parse type 21 too (https://github.com/tailscale/tailscale/issues/532)
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c.logf("netlink msg %+v, %q", msg.Header, msg.Data)
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return unspecifiedMessage{}, nil
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}
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}
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func netaddrIP(std net.IP) netaddr.IP {
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ip, _ := netaddr.FromStdIP(std)
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return ip
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}
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// newRouteMessage is a message for a new route being added.
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type newRouteMessage struct {
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Src, Dst, Gateway netaddr.IP
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Table uint8
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}
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func (m *newRouteMessage) ignore() bool {
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return m.Table == 88 || tsaddr.IsTailscaleIP(m.Dst)
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}
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// newAddrMessage is a message for a new address being added.
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type newAddrMessage struct {
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Addr netaddr.IP
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Label string // netlink Label attribute (e.g. "tailscale0")
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}
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func (m *newAddrMessage) ignore() bool {
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return tsaddr.IsTailscaleIP(m.Addr)
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}
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