platform: don't replace routes that already exist

If a route already exists that matches the network, prefix, gateway,
and metric of a route NM would like to add, don't try to overwrite
the route.

Unlike IP addresses, the kernel doesn't update the details, it
appears to completely replace that route, which might screw up
external tools that added the route originally.

One example of this is IPSec via openswan/libreswan.  They add the
routes to the kernel upon connection, and if NM replaces those routes,
IPSec no longer works.  While this may be due to kernel bugs or
bad handling of route replacement, there's no reason for NM to touch
routes that it wouldn't materially change anyway.

(yes, we could perhaps use NLM_F_REPLACE in add_kernel_object() only
when we really wanted to replace something, but why ask the kernel
to do the work when it's not required anyway?)

1 files changed, 32 insertions, 16 deletions

diff --git a/src/platform/nm-platform.c b/src/platform/nm-platform.c
index 01c02461e8..9267c36441 100644
--- a/src/platform/nm-platform.c
+++ b/src/platform/nm-platform.c
@@ -1606,6 +1606,7 @@ nm_platform_ip4_route_sync (int ifindex, const GArray *known_routes)
 	GArray *routes;
 	NMPlatformIP4Route *route;
 	const NMPlatformIP4Route *known_route;
+	gboolean success;
 	int i;
 
 	/* Delete unknown routes */
@@ -1616,22 +1617,29 @@ nm_platform_ip4_route_sync (int ifindex, const GArray *known_routes)
 		if (!array_contains_ip4_route (known_routes, route))
 			nm_platform_ip4_route_delete (ifindex, route->network, route->plen, route->metric);
 	}
-	g_array_free (routes, TRUE);
 
-	if (!known_routes)
+	if (!known_routes) {
+		g_array_free (routes, TRUE);
 		return TRUE;
+	}
 
 	/* Add missing routes */
-	for (i = 0; i < known_routes->len; i++) {
+	for (i = 0, success = TRUE; i < known_routes->len && success; i++) {
 		known_route = &g_array_index (known_routes, NMPlatformIP4Route, i);
 
-		if (!nm_platform_ip4_route_add (ifindex,
-				known_route->network, known_route->plen, known_route->gateway,
-				known_route->metric, known_route->mss))
-			return FALSE;
+		/* Ignore routes that already exist */
+		if (!array_contains_ip4_route (routes, known_route)) {
+			success = nm_platform_ip4_route_add (ifindex,
+			                                     known_route->network,
+			                                     known_route->plen,
+			                                     known_route->gateway,
+			                                     known_route->metric,
+			                                     known_route->mss);
+		}
 	}
 
-	return TRUE;
+	g_array_free (routes, TRUE);
+	return success;
 }
 
 /**
@@ -1651,6 +1659,7 @@ nm_platform_ip6_route_sync (int ifindex, const GArray *known_routes)
 	GArray *routes;
 	NMPlatformIP6Route *route;
 	const NMPlatformIP6Route *known_route;
+	gboolean success;
 	int i;
 
 	/* Delete unknown routes */
@@ -1662,22 +1671,29 @@ nm_platform_ip6_route_sync (int ifindex, const GArray *known_routes)
 		if (!array_contains_ip6_route (known_routes, route))
 			nm_platform_ip6_route_delete (ifindex, route->network, route->plen, route->metric);
 	}
-	g_array_free (routes, TRUE);
 
-	if (!known_routes)
+	if (!known_routes) {
+		g_array_free (routes, TRUE);
 		return TRUE;
+	}
 
 	/* Add missing routes */
-	for (i = 0; i < known_routes->len; i++) {
+	for (i = 0, success = TRUE; i < known_routes->len && success; i++) {
 		known_route = &g_array_index (known_routes, NMPlatformIP6Route, i);
 
-		if (!nm_platform_ip6_route_add (ifindex,
-				known_route->network, known_route->plen, known_route->gateway,
-				known_route->metric, known_route->mss))
-			return FALSE;
+		/* Ignore routes that already exist */
+		if (!array_contains_ip6_route (routes, known_route)) {
+			success = nm_platform_ip6_route_add (ifindex,
+			                                     known_route->network,
+			                                     known_route->plen,
+			                                     known_route->gateway,
+			                                     known_route->metric,
+			                                     known_route->mss);
+		}
 	}
 
-	return TRUE;
+	g_array_free (routes, TRUE);
+	return success;
 }
 
 gboolean