Revert "Rollback new routing functionality (#1805)" (#1813)

This reverts commit 9f32ccd453.

client/internal/routemanager/routemanager.go

@@ -0,0 +1,126 @@
+//go:build !android && !ios
+
+package routemanager
+
+import (
+	"errors"
+	"fmt"
+	"net/netip"
+	"sync"
+
+	"github.com/hashicorp/go-multierror"
+	log "github.com/sirupsen/logrus"
+
+	nbnet "github.com/netbirdio/netbird/util/net"
+)
+
+type ref struct {
+	count   int
+	nexthop netip.Addr
+	intf    string
+}
+
+type RouteManager struct {
+	// refCountMap keeps track of the reference ref for prefixes
+	refCountMap map[netip.Prefix]ref
+	// prefixMap keeps track of the prefixes associated with a connection ID for removal
+	prefixMap   map[nbnet.ConnectionID][]netip.Prefix
+	addRoute    AddRouteFunc
+	removeRoute RemoveRouteFunc
+	mutex       sync.Mutex
+}
+
+type AddRouteFunc func(prefix netip.Prefix) (nexthop netip.Addr, intf string, err error)
+type RemoveRouteFunc func(prefix netip.Prefix, nexthop netip.Addr, intf string) error
+
+func NewRouteManager(addRoute AddRouteFunc, removeRoute RemoveRouteFunc) *RouteManager {
+	// TODO: read initial routing table into refCountMap
+	return &RouteManager{
+		refCountMap: map[netip.Prefix]ref{},
+		prefixMap:   map[nbnet.ConnectionID][]netip.Prefix{},
+		addRoute:    addRoute,
+		removeRoute: removeRoute,
+	}
+}
+
+func (rm *RouteManager) AddRouteRef(connID nbnet.ConnectionID, prefix netip.Prefix) error {
+	rm.mutex.Lock()
+	defer rm.mutex.Unlock()
+
+	ref := rm.refCountMap[prefix]
+	log.Debugf("Increasing route ref count %d for prefix %s", ref.count, prefix)
+
+	// Add route to the system, only if it's a new prefix
+	if ref.count == 0 {
+		log.Debugf("Adding route for prefix %s", prefix)
+		nexthop, intf, err := rm.addRoute(prefix)
+		if errors.Is(err, ErrRouteNotFound) {
+			return nil
+		}
+		if errors.Is(err, ErrRouteNotAllowed) {
+			log.Debugf("Adding route for prefix %s: %s", prefix, err)
+		}
+		if err != nil {
+			return fmt.Errorf("failed to add route for prefix %s: %w", prefix, err)
+		}
+		ref.nexthop = nexthop
+		ref.intf = intf
+	}
+
+	ref.count++
+	rm.refCountMap[prefix] = ref
+	rm.prefixMap[connID] = append(rm.prefixMap[connID], prefix)
+
+	return nil
+}
+
+func (rm *RouteManager) RemoveRouteRef(connID nbnet.ConnectionID) error {
+	rm.mutex.Lock()
+	defer rm.mutex.Unlock()
+
+	prefixes, ok := rm.prefixMap[connID]
+	if !ok {
+		log.Debugf("No prefixes found for connection ID %s", connID)
+		return nil
+	}
+
+	var result *multierror.Error
+	for _, prefix := range prefixes {
+		ref := rm.refCountMap[prefix]
+		log.Debugf("Decreasing route ref count %d for prefix %s", ref.count, prefix)
+		if ref.count == 1 {
+			log.Debugf("Removing route for prefix %s", prefix)
+			// TODO: don't fail if the route is not found
+			if err := rm.removeRoute(prefix, ref.nexthop, ref.intf); err != nil {
+				result = multierror.Append(result, fmt.Errorf("remove route for prefix %s: %w", prefix, err))
+				continue
+			}
+			delete(rm.refCountMap, prefix)
+		} else {
+			ref.count--
+			rm.refCountMap[prefix] = ref
+		}
+	}
+	delete(rm.prefixMap, connID)
+
+	return result.ErrorOrNil()
+}
+
+// Flush removes all references and routes from the system
+func (rm *RouteManager) Flush() error {
+	rm.mutex.Lock()
+	defer rm.mutex.Unlock()
+
+	var result *multierror.Error
+	for prefix := range rm.refCountMap {
+		log.Debugf("Removing route for prefix %s", prefix)
+		ref := rm.refCountMap[prefix]
+		if err := rm.removeRoute(prefix, ref.nexthop, ref.intf); err != nil {
+			result = multierror.Append(result, fmt.Errorf("remove route for prefix %s: %w", prefix, err))
+		}
+	}
+	rm.refCountMap = map[netip.Prefix]ref{}
+	rm.prefixMap = map[nbnet.ConnectionID][]netip.Prefix{}
+
+	return result.ErrorOrNil()
+}