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Most operating systems add a /32 route for the default gateway address to its routing table This will allow routes to be configured into the system even when the incoming range contains the default gateway. In case a range is a sub-range of an existing route and this range happens to contain the default gateway it attempts to create a default gateway route to prevent loop issues
121 lines
2.9 KiB
Go
121 lines
2.9 KiB
Go
//go:build !android
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package routemanager
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import (
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"fmt"
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"net"
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"net/netip"
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"github.com/libp2p/go-netroute"
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log "github.com/sirupsen/logrus"
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)
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var errRouteNotFound = fmt.Errorf("route not found")
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func addToRouteTableIfNoExists(prefix netip.Prefix, addr string) error {
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ok, err := existsInRouteTable(prefix)
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if err != nil {
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return err
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}
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if ok {
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log.Warnf("skipping adding a new route for network %s because it already exists", prefix)
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return nil
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}
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ok, err = isSubRange(prefix)
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if err != nil {
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return err
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}
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if ok {
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err := addRouteForCurrentDefaultGateway(prefix)
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if err != nil {
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log.Warnf("unable to add route for current default gateway route. Will proceed without it. error: %s", err)
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}
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}
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return addToRouteTable(prefix, addr)
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}
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func addRouteForCurrentDefaultGateway(prefix netip.Prefix) error {
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defaultGateway, err := getExistingRIBRouteGateway(netip.MustParsePrefix("0.0.0.0/0"))
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if err != nil && err != errRouteNotFound {
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return err
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}
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addr := netip.MustParseAddr(defaultGateway.String())
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if !prefix.Contains(addr) {
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log.Debugf("skipping adding a new route for gateway %s because it is not in the network %s", addr, prefix)
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return nil
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}
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gatewayPrefix := netip.PrefixFrom(addr, 32)
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ok, err := existsInRouteTable(gatewayPrefix)
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if err != nil {
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return fmt.Errorf("unable to check if there is an existing route for gateway %s. error: %s", gatewayPrefix, err)
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}
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if ok {
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log.Debugf("skipping adding a new route for gateway %s because it already exists", gatewayPrefix)
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return nil
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}
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gatewayHop, err := getExistingRIBRouteGateway(gatewayPrefix)
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if err != nil && err != errRouteNotFound {
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return fmt.Errorf("unable to get the next hop for the default gateway address. error: %s", err)
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}
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log.Debugf("adding a new route for gateway %s with next hop %s", gatewayPrefix, gatewayHop)
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return addToRouteTable(gatewayPrefix, gatewayHop.String())
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}
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func existsInRouteTable(prefix netip.Prefix) (bool, error) {
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routes, err := getRoutesFromTable()
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if err != nil {
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return false, err
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}
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for _, tableRoute := range routes {
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if tableRoute == prefix {
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return true, nil
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}
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}
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return false, nil
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}
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func isSubRange(prefix netip.Prefix) (bool, error) {
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routes, err := getRoutesFromTable()
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if err != nil {
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return false, err
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}
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for _, tableRoute := range routes {
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if tableRoute.Bits() > minRangeBits && tableRoute.Contains(prefix.Addr()) && tableRoute.Bits() < prefix.Bits() {
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return true, nil
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}
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}
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return false, nil
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}
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func removeFromRouteTableIfNonSystem(prefix netip.Prefix, addr string) error {
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return removeFromRouteTable(prefix, addr)
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}
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func getExistingRIBRouteGateway(prefix netip.Prefix) (net.IP, error) {
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r, err := netroute.New()
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if err != nil {
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return nil, err
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}
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_, gateway, preferredSrc, err := r.Route(prefix.Addr().AsSlice())
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if err != nil {
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log.Errorf("getting routes returned an error: %v", err)
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return nil, errRouteNotFound
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}
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if gateway == nil {
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return preferredSrc, nil
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}
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return gateway, nil
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}
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