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tailscale/wgengine/monitor/monitor_linux.go

137 lines
3.9 KiB
Go

// 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.
// +build !android
package monitor
import (
"fmt"
"net"
"time"
"github.com/jsimonetti/rtnetlink"
"github.com/mdlayher/netlink"
"golang.org/x/sys/unix"
"inet.af/netaddr"
"tailscale.com/net/tsaddr"
"tailscale.com/types/logger"
)
// unspecifiedMessage is a minimal message implementation that should not
// be ignored. In general, OS-specific implementations should use better
// types and avoid this if they can.
type unspecifiedMessage struct{}
func (unspecifiedMessage) ignore() bool { return false }
// 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 {
logf logger.Logf
conn *netlink.Conn
buffered []netlink.Message
}
func newOSMon(logf logger.Logf) (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{logf: logf, conn: 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) {
if len(c.buffered) == 0 {
var err error
c.buffered, err = c.conn.Receive()
if err != nil {
return nil, err
}
if len(c.buffered) == 0 {
// Unexpected. Not seen in wild, but sleep defensively.
time.Sleep(time.Second)
return ignoreMessage{}, nil
}
}
msg := c.buffered[0]
c.buffered = c.buffered[1:]
// See https://github.com/torvalds/linux/blob/master/include/uapi/linux/rtnetlink.h
// And https://man7.org/linux/man-pages/man7/rtnetlink.7.html
switch msg.Header.Type {
case unix.RTM_NEWADDR, unix.RTM_DELADDR:
var rmsg rtnetlink.AddressMessage
if err := rmsg.UnmarshalBinary(msg.Data); err != nil {
c.logf("failed to parse type 0x%x: %v", msg.Header.Type, err)
return unspecifiedMessage{}, nil
}
return &newAddrMessage{
Label: rmsg.Attributes.Label,
Addr: netaddrIP(rmsg.Attributes.Local),
Delete: msg.Header.Type == unix.RTM_DELADDR,
}, nil
case unix.RTM_NEWROUTE:
var rmsg rtnetlink.RouteMessage
if err := rmsg.UnmarshalBinary(msg.Data); err != nil {
c.logf("RTM_NEWROUTE: failed to parse: %v", err)
return unspecifiedMessage{}, nil
}
return &newRouteMessage{
Table: rmsg.Table,
Src: netaddrIP(rmsg.Attributes.Src),
Dst: netaddrIP(rmsg.Attributes.Dst),
Gateway: netaddrIP(rmsg.Attributes.Gateway),
}, nil
default:
c.logf("unhandled netlink msg type 0x%x: %+v, %q", msg.Header.Type, msg.Header, msg.Data)
return unspecifiedMessage{}, nil
}
}
func netaddrIP(std net.IP) netaddr.IP {
ip, _ := netaddr.FromStdIP(std)
return ip
}
// newRouteMessage is a message for a new route being added.
type newRouteMessage struct {
Src, Dst, Gateway netaddr.IP
Table uint8
}
func (m *newRouteMessage) ignore() bool {
return m.Table == 88 || tsaddr.IsTailscaleIP(m.Dst)
}
// newAddrMessage is a message for a new address being added.
type newAddrMessage struct {
Delete bool
Addr netaddr.IP
Label string // netlink Label attribute (e.g. "tailscale0")
}
func (m *newAddrMessage) ignore() bool {
return tsaddr.IsTailscaleIP(m.Addr)
}
type ignoreMessage struct{}
func (ignoreMessage) ignore() bool { return true }