From 4c556203d93fdd143630431dded4e0e6ea24824e Mon Sep 17 00:00:00 2001

From: Thomas Haller <thaller@redhat.com>

Date: Thu, 9 Jun 2022 10:00:47 +0200

Subject: [PATCH 1/1] platform: workaround for preserving IPv6 address order

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/ ## 1021

---

 src/libnm-platform/nm-platform.c | 15 +++++++++++++++

 1 file changed, 15 insertions(+)

diff --git a/src/libnm-platform/nm-platform.c b/src/libnm-platform/nm-platform.c

index f264ed7a45b2..120e50b3c772 100644

--- a/src/libnm-platform/nm-platform.c

+++ b/src/libnm-platform/nm-platform.c

@@ -3961,45 +3961,60 @@ nm_platform_ip_address_sync(NMPlatform *self,

         for (i = 0; i < addresses_prune->len; i++) {

             const NMPObject *prune_obj = addresses_prune->pdata[i];

             nm_assert(NM_IN_SET(NMP_OBJECT_GET_TYPE(prune_obj),

                                 NMP_OBJECT_TYPE_IP4_ADDRESS,

                                 NMP_OBJECT_TYPE_IP6_ADDRESS));

             if (nm_g_hash_table_contains(known_addresses_idx, prune_obj))

                 continue;

             nm_platform_ip_address_delete(self,

                                           addr_family,

                                           ifindex,

                                           NMP_OBJECT_CAST_IP_ADDRESS(prune_obj));

         }

     }

     /* @plat_addresses for IPv6 must be sorted in decreasing priority order (highest priority addresses first).

      * IPv4 are probably unsorted or sorted with lowest priority first, but their order doesn't matter because

      * we check the "secondary" flag. */

+    if (IS_IPv4) {

     plat_addresses = nm_platform_lookup_clone(

         self,

         nmp_lookup_init_object(&lookup, NMP_OBJECT_TYPE_IP_ADDRESS(IS_IPv4), ifindex),

         NULL,

         NULL);

+    } else {

+        /* HACK: early 1.36 versions had a bug of not actually reordering the IPv6 addresses.

+         * This was fixed by commit cd4601802de5 ('platform: fix address order in

+         * nm_platform_ip_address_sync()').

+         *

+         * However, also in 1.36, the actually implemented order of IPv6 addresses is not

+         * the one we want ([1]). So disable the fix again, to not reorder IPv6 addresses.

+         *

+         * The effect is, that DHCPv6 addresses end up being preferred over SLAAC, because

+         * they get added later during activation. Of course, if any address gets added

+         * even later (like a new router appearing), then the order will be wrong again.

+         *

+         * [1] https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/1021 */

+    }

     if (nm_g_ptr_array_len(plat_addresses) > 0) {

         /* Delete addresses that interfere with our intended order. */

         if (IS_IPv4) {

             GHashTable   *known_subnets = NULL;

             GHashTable   *plat_subnets;

             gs_free bool *plat_handled_to_free = NULL;

             bool         *plat_handled         = NULL;

             /* For IPv4, we only consider it a conflict for addresses in the same

              * subnet. That's where kernel will assign a primary/secondary flag.

              * For different subnets, we don't define the order. */

             plat_subnets = ip4_addr_subnets_build_index(plat_addresses, TRUE, TRUE);

             for (i = 0; i < plat_addresses->len; i++) {

                 const NMPObject            *plat_obj = plat_addresses->pdata[i];

                 const NMPObject            *known_obj;

                 const NMPlatformIP4Address *plat_address;

                 const GPtrArray            *addr_list;

-- 

2.36.1