From 55b3bfe8f66242ae0fc228c9e5048b72e4048a8c Mon Sep 17 00:00:00 2001
From: Michael Cambria <mcambria@redhat.com>
Date: Thu, 11 Mar 2021 13:49:00 -0500
Subject: [PATCH] Allow multiple routes to be added for the same prefix.
 Enables ECMP

Fixes: https://github.com/containernetworking/plugins/issues/601

Signed-off-by: Michael Cambria <mcambria@redhat.com>
---
 pkg/ipam/ipam_linux.go                              | 13 ++++++++-----
 plugins/main/bridge/bridge.go                       |  2 +-
 .../github.com/vishvananda/netlink/route_linux.go   | 12 ++++++++++++
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/pkg/ipam/ipam_linux.go b/pkg/ipam/ipam_linux.go
index bf16cb0ff..8c8b8e0b0 100644
--- a/pkg/ipam/ipam_linux.go
+++ b/pkg/ipam/ipam_linux.go
@@ -113,11 +113,14 @@ func ConfigureIface(ifName string, res *current.Result) error {
 				gw = v6gw
 			}
 		}
-		if err = ip.AddRoute(&r.Dst, gw, link); err != nil {
-			// we skip over duplicate routes as we assume the first one wins
-			if !os.IsExist(err) {
-				return fmt.Errorf("failed to add route '%v via %v dev %v': %v", r.Dst, gw, ifName, err)
-			}
+		route := netlink.Route{
+			Dst:       &r.Dst,
+			LinkIndex: link.Attrs().Index,
+			Gw:        gw,
+		}
+
+		if err = netlink.RouteAddEcmp(&route); err != nil {
+			return fmt.Errorf("failed to add route '%v via %v dev %v': %v", r.Dst, gw, ifName, err)
 		}
 	}
 
diff --git a/plugins/main/bridge/bridge.go b/plugins/main/bridge/bridge.go
index 69ffa98f1..638b70922 100644
--- a/plugins/main/bridge/bridge.go
+++ b/plugins/main/bridge/bridge.go
@@ -122,7 +122,7 @@ func calcGateways(result *current.Result, n *NetConf) (*gwInfo, *gwInfo, error)
 
 		// Add a default route for this family using the current
 		// gateway address if necessary.
-		if n.IsDefaultGW && !gws.defaultRouteFound {
+		if n.IsDefaultGW {
 			for _, route := range result.Routes {
 				if route.GW != nil && defaultNet.String() == route.Dst.String() {
 					gws.defaultRouteFound = true
diff --git a/vendor/github.com/vishvananda/netlink/route_linux.go b/vendor/github.com/vishvananda/netlink/route_linux.go
index 4e778a417..5dec39a38 100644
--- a/vendor/github.com/vishvananda/netlink/route_linux.go
+++ b/vendor/github.com/vishvananda/netlink/route_linux.go
@@ -466,6 +466,18 @@ func RouteReplace(route *Route) error {
 	return pkgHandle.RouteReplace(route)
 }
 
+// RouteAddEcmp will add a route to the system.
+func RouteAddEcmp(route *Route) error {
+        return pkgHandle.RouteAddEcmp(route)
+}
+
+// RouteAddEcmp will add a route to the system.
+func (h *Handle) RouteAddEcmp(route *Route) error {
+        flags := unix.NLM_F_CREATE | unix.NLM_F_ACK
+        req := h.newNetlinkRequest(unix.RTM_NEWROUTE, flags)
+        return h.routeHandle(route, req, nl.NewRtMsg())
+}
+
 // RouteReplace will add a route to the system.
 // Equivalent to: `ip route replace $route`
 func (h *Handle) RouteReplace(route *Route) error {