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@@ -11,12 +11,16 @@ import (
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"fmt"
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"io"
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"log"
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+ "net"
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"os"
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"os/exec"
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"runtime"
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"strings"
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+ "github.com/jsimonetti/rtnetlink"
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+ "github.com/mdlayher/netlink"
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"go4.org/mem"
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+ "golang.org/x/sys/unix"
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"inet.af/netaddr"
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"tailscale.com/syncs"
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"tailscale.com/util/lineread"
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@@ -70,9 +74,7 @@ func likelyHomeRouterIPLinux() (ret netaddr.IP, ok bool) {
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if err != nil {
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return nil // ignore error, skip line and keep going
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}
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- const RTF_UP = 0x0001
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- const RTF_GATEWAY = 0x0002
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- if flags&(RTF_UP|RTF_GATEWAY) != RTF_UP|RTF_GATEWAY {
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+ if flags&(unix.RTF_UP|unix.RTF_GATEWAY) != unix.RTF_UP|unix.RTF_GATEWAY {
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return nil
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}
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ipu32, err := mem.ParseUint(gwHex, 16, 32)
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@@ -145,7 +147,62 @@ func defaultRoute() (d DefaultRouteDetails, err error) {
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d.InterfaceName = v
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return d, err
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}
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- return d, err
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+ // Issue 4038: the default route (such as on Unifi UDM Pro)
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+ // might be in a non-default table, so it won't show up in
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+ // /proc/net/route. Use netlink to find the default route.
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+ //
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+ // TODO(bradfitz): this allocates a fair bit. We should track
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+ // this in wgengine/monitor instead and have
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+ // interfaces.GetState take a link monitor or similar so the
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+ // routing table can be cached and the monitor's existing
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+ // subscription to route changes can update the cached state,
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+ // rather than querying the whole thing every time like
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+ // defaultRouteFromNetlink does.
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+ //
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+ // Then we should just always try to use the cached route
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+ // table from netlink every time, and only use /proc/net/route
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+ // as a fallback for weird environments where netlink might be
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+ // banned but /proc/net/route is emulated (e.g. stuff like
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+ // Cloud Run?).
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+ return defaultRouteFromNetlink()
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+}
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+
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+func defaultRouteFromNetlink() (d DefaultRouteDetails, err error) {
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+ c, err := rtnetlink.Dial(&netlink.Config{Strict: true})
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+ if err != nil {
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+ return d, fmt.Errorf("defaultRouteFromNetlink: Dial: %w", err)
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+ }
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+ defer c.Close()
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+ rms, err := c.Route.List()
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+ if err != nil {
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+ return d, fmt.Errorf("defaultRouteFromNetlink: List: %w", err)
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+ }
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+ for _, rm := range rms {
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+ if rm.Attributes.Gateway == nil {
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+ // A default route has a gateway. If it doesn't, skip it.
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+ continue
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+ }
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+ if rm.Attributes.Dst != nil {
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+ // A default route has a nil destination to mean anything
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+ // so ignore any route for a specific destination.
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+ // TODO(bradfitz): better heuristic?
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+ // empirically this seems like enough.
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+ continue
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+ }
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+ // TODO(bradfitz): care about address family, if
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+ // callers ever start caring about v4-vs-v6 default
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+ // route differences.
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+ idx := int(rm.Attributes.OutIface)
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+ if idx == 0 {
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+ continue
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+ }
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+ if iface, err := net.InterfaceByIndex(idx); err == nil {
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+ d.InterfaceName = iface.Name
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+ d.InterfaceIndex = idx
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+ return d, nil
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+ }
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+ }
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+ return d, errNoDefaultRoute
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}
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var zeroRouteBytes = []byte("00000000")
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@@ -155,6 +212,8 @@ var procNetRoutePath = "/proc/net/route"
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// /proc/net/route looking for a default route.
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const maxProcNetRouteRead = 1000
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+var errNoDefaultRoute = errors.New("no default route found")
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+
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func defaultRouteInterfaceProcNetInternal(bufsize int) (string, error) {
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f, err := os.Open(procNetRoutePath)
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if err != nil {
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@@ -168,7 +227,7 @@ func defaultRouteInterfaceProcNetInternal(bufsize int) (string, error) {
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lineNum++
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line, err := br.ReadSlice('\n')
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if err == io.EOF || lineNum > maxProcNetRouteRead {
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- return "", fmt.Errorf("no default routes found: %w", err)
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+ return "", errNoDefaultRoute
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}
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if err != nil {
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return "", err
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Brad Fitzpatrick