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b9adbe2002
In prep for most of the package funcs in net/interfaces to become methods in a long-lived netmon.Monitor that can cache things. (Many of the funcs are very heavy to call regularly, whereas the long-lived netmon.Monitor can subscribe to things from the OS and remember answers to questions it's asked regularly later) Updates tailscale/corp#10910 Updates tailscale/corp#18960 Updates #7967 Updates #3299 Change-Id: Ie4e8dedb70136af2d611b990b865a822cd1797e5 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
112 lines
3.1 KiB
Go
112 lines
3.1 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package netmon
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import (
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"fmt"
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"net"
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"strings"
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"sync"
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"syscall"
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"unsafe"
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"golang.org/x/net/route"
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"golang.org/x/sys/unix"
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"tailscale.com/util/mak"
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)
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// fetchRoutingTable calls route.FetchRIB, fetching NET_RT_DUMP2.
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func fetchRoutingTable() (rib []byte, err error) {
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return route.FetchRIB(syscall.AF_UNSPEC, syscall.NET_RT_DUMP2, 0)
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}
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func parseRoutingTable(rib []byte) ([]route.Message, error) {
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return route.ParseRIB(syscall.NET_RT_IFLIST2, rib)
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}
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var ifNames struct {
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sync.Mutex
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m map[int]string // ifindex => name
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}
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func init() {
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interfaceDebugExtras = interfaceDebugExtrasDarwin
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}
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// getDelegatedInterface returns the interface index of the underlying interface
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// for the given interface index. 0 is returned if the interface does not
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// delegate.
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func getDelegatedInterface(ifIndex int) (int, error) {
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ifNames.Lock()
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defer ifNames.Unlock()
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// To get the delegated interface, we do what ifconfig does and use the
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// SIOCGIFDELEGATE ioctl. It operates in term of a ifreq struct, which
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// has to be populated with a interface name. To avoid having to do a
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// interface index -> name lookup every time, we cache interface names
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// (since indexes and names are stable after boot).
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ifName, ok := ifNames.m[ifIndex]
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if !ok {
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iface, err := net.InterfaceByIndex(ifIndex)
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if err != nil {
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return 0, err
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}
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ifName = iface.Name
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mak.Set(&ifNames.m, ifIndex, ifName)
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}
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// Only tunnels (like Tailscale itself) have a delegated interface, avoid
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// the ioctl if we can.
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if !strings.HasPrefix(ifName, "utun") {
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return 0, nil
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}
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// We don't cache the result of the ioctl, since the delegated interface can
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// change, e.g. if the user changes the preferred service order in the
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// network preference pane.
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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
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if err != nil {
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return 0, err
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}
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defer unix.Close(fd)
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// Match the ifreq struct/union from the bsd/net/if.h header in the Darwin
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// open source release.
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var ifr struct {
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ifr_name [unix.IFNAMSIZ]byte
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ifr_delegated uint32
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}
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copy(ifr.ifr_name[:], ifName)
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// SIOCGIFDELEGATE is not in the Go x/sys package or in the public macOS
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// <sys/sockio.h> headers. However, it is in the Darwin/xnu open source
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// release (and is used by ifconfig, see
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// https://github.com/apple-oss-distributions/network_cmds/blob/6ccdc225ad5aa0d23ea5e7d374956245d2462427/ifconfig.tproj/ifconfig.c#L2183-L2187).
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// We generate its value by evaluating the `_IOWR('i', 157, struct ifreq)`
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// macro, which is how it's defined in
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// https://github.com/apple/darwin-xnu/blob/2ff845c2e033bd0ff64b5b6aa6063a1f8f65aa32/bsd/sys/sockio.h#L264
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const SIOCGIFDELEGATE = 0xc020699d
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_, _, errno := syscall.Syscall(
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syscall.SYS_IOCTL,
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uintptr(fd),
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uintptr(SIOCGIFDELEGATE),
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uintptr(unsafe.Pointer(&ifr)))
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if errno != 0 {
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return 0, errno
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}
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return int(ifr.ifr_delegated), nil
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}
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func interfaceDebugExtrasDarwin(ifIndex int) (string, error) {
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delegated, err := getDelegatedInterface(ifIndex)
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if err != nil {
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return "", err
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}
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if delegated == 0 {
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return "", nil
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}
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return fmt.Sprintf("delegated=%d", delegated), nil
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}
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