platform: interpret metric_any for routes to accept offset for default metric

The DHCP client likes to order multiple default routes by adding
them with different, increasing metric.

To support that, let "metric_any" not completely disable the "metric"
field, but instead interpret it as an offset that should be added to
the default metric.

3 files changed, 85 insertions, 78 deletions

diff --git a/src/nm-l3-config-data.c b/src/nm-l3-config-data.c
index ef8d67a8f9..9b1e017b14 100644
--- a/src/nm-l3-config-data.c
+++ b/src/nm-l3-config-data.c
@@ -2600,7 +2600,7 @@ nm_l3_config_data_merge(NML3ConfigData *      self,
                 if (r_src->metric_any) {
                     _ensure_r();
                     r.rx.metric_any = FALSE;
-                    r.rx.metric     = default_route_metric_x[IS_IPv4];
+                    r.rx.metric = nm_add_u32_clamped(r.rx.metric, default_route_metric_x[IS_IPv4]);
                 }
 
                 if (NM_PLATFORM_IP_ROUTE_IS_DEFAULT(r_src)) {
diff --git a/src/platform/nm-platform.c b/src/platform/nm-platform.c
index eca201b087..ca5080b009 100644
--- a/src/platform/nm-platform.c
+++ b/src/platform/nm-platform.c
@@ -6515,7 +6515,9 @@ nm_platform_ip4_route_to_string(const NMPlatformIP4Route *route, char *buf, gsiz
         route->plen,
         s_gateway,
         str_dev,
-        route->metric_any ? "??" : nm_sprintf_buf(str_metric, "%u", route->metric),
+        route->metric_any
+            ? (route->metric ? nm_sprintf_buf(str_metric, "??+%u", route->metric) : "??")
+            : nm_sprintf_buf(str_metric, "%u", route->metric),
         route->mss,
         nmp_utils_ip_config_source_to_string(route->rt_source, s_source, sizeof(s_source)),
         _rtm_flags_to_string_full(str_rtm_flags, sizeof(str_rtm_flags), route->r_rtm_flags),
@@ -6639,7 +6641,9 @@ nm_platform_ip6_route_to_string(const NMPlatformIP6Route *route, char *buf, gsiz
         route->plen,
         s_gateway,
         str_dev,
-        route->metric_any ? "??" : nm_sprintf_buf(str_metric, "%u", route->metric),
+        route->metric_any
+            ? (route->metric ? nm_sprintf_buf(str_metric, "??+%u", route->metric) : "??")
+            : nm_sprintf_buf(str_metric, "%u", route->metric),
         route->mss,
         nmp_utils_ip_config_source_to_string(route->rt_source, s_source, sizeof(s_source)),
         route->src_plen || !IN6_IS_ADDR_UNSPECIFIED(&route->src)
@@ -7927,7 +7931,7 @@ nm_platform_ip4_route_hash_update(const NMPlatformIP4Route *obj,
             nm_platform_ip_route_get_effective_table(NM_PLATFORM_IP_ROUTE_CAST(obj)),
             nm_utils_ip4_address_clear_host_address(obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip4_route_get_effective_metric(obj),
+            obj->metric,
             obj->tos,
             NM_HASH_COMBINE_BOOLS(guint8, obj->metric_any, obj->table_any));
         break;
@@ -7938,7 +7942,7 @@ nm_platform_ip4_route_hash_update(const NMPlatformIP4Route *obj,
             nm_platform_ip_route_get_effective_table(NM_PLATFORM_IP_ROUTE_CAST(obj)),
             nm_utils_ip4_address_clear_host_address(obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip4_route_get_effective_metric(obj),
+            obj->metric,
             obj->tos,
             /* on top of WEAK_ID: */
             obj->ifindex,
@@ -7970,7 +7974,7 @@ nm_platform_ip4_route_hash_update(const NMPlatformIP4Route *obj,
             obj->ifindex,
             nm_utils_ip4_address_clear_host_address(obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip4_route_get_effective_metric(obj),
+            obj->metric,
             obj->gateway,
             nmp_utils_ip_config_source_round_trip_rtprot(obj->rt_source),
             _ip_route_scope_inv_get_normalized(obj),
@@ -7999,7 +8003,7 @@ nm_platform_ip4_route_hash_update(const NMPlatformIP4Route *obj,
                             obj->ifindex,
                             obj->network,
                             obj->plen,
-                            nm_platform_ip4_route_get_effective_metric(obj),
+                            obj->metric,
                             obj->gateway,
                             obj->rt_source,
                             obj->scope_inv,
@@ -8039,8 +8043,7 @@ nm_platform_ip4_route_cmp(const NMPlatformIP4Route *a,
         NM_CMP_DIRECT_IN4ADDR_SAME_PREFIX(a->network, b->network, MIN(a->plen, b->plen));
         NM_CMP_FIELD(a, b, plen);
         NM_CMP_FIELD_UNSAFE(a, b, metric_any);
-        if (!a->metric_any)
-            NM_CMP_FIELD(a, b, metric);
+        NM_CMP_FIELD(a, b, metric);
         NM_CMP_FIELD(a, b, tos);
         if (cmp_type == NM_PLATFORM_IP_ROUTE_CMP_TYPE_ID) {
             NM_CMP_FIELD(a, b, ifindex);
@@ -8081,8 +8084,7 @@ nm_platform_ip4_route_cmp(const NMPlatformIP4Route *a,
             NM_CMP_FIELD(a, b, network);
         NM_CMP_FIELD(a, b, plen);
         NM_CMP_FIELD_UNSAFE(a, b, metric_any);
-        if (!a->metric_any)
-            NM_CMP_FIELD(a, b, metric);
+        NM_CMP_FIELD(a, b, metric);
         NM_CMP_FIELD(a, b, gateway);
         if (cmp_type == NM_PLATFORM_IP_ROUTE_CMP_TYPE_SEMANTICALLY) {
             NM_CMP_DIRECT(nmp_utils_ip_config_source_round_trip_rtprot(a->rt_source),
@@ -8130,7 +8132,7 @@ nm_platform_ip6_route_hash_update(const NMPlatformIP6Route *obj,
             nm_platform_ip_route_get_effective_table(NM_PLATFORM_IP_ROUTE_CAST(obj)),
             *nm_utils_ip6_address_clear_host_address(&a1, &obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip6_route_get_effective_metric(obj),
+            obj->metric,
             *nm_utils_ip6_address_clear_host_address(&a2, &obj->src, obj->src_plen),
             obj->src_plen,
             NM_HASH_COMBINE_BOOLS(guint8, obj->metric_any, obj->table_any));
@@ -8142,7 +8144,7 @@ nm_platform_ip6_route_hash_update(const NMPlatformIP6Route *obj,
             nm_platform_ip_route_get_effective_table(NM_PLATFORM_IP_ROUTE_CAST(obj)),
             *nm_utils_ip6_address_clear_host_address(&a1, &obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip6_route_get_effective_metric(obj),
+            obj->metric,
             *nm_utils_ip6_address_clear_host_address(&a2, &obj->src, obj->src_plen),
             obj->src_plen,
             NM_HASH_COMBINE_BOOLS(guint8, obj->metric_any, obj->table_any),
@@ -8158,7 +8160,7 @@ nm_platform_ip6_route_hash_update(const NMPlatformIP6Route *obj,
             obj->ifindex,
             *nm_utils_ip6_address_clear_host_address(&a1, &obj->network, obj->plen),
             obj->plen,
-            nm_platform_ip6_route_get_effective_metric(obj),
+            obj->metric,
             obj->gateway,
             obj->pref_src,
             *nm_utils_ip6_address_clear_host_address(&a2, &obj->src, obj->src_plen),
@@ -8187,7 +8189,7 @@ nm_platform_ip6_route_hash_update(const NMPlatformIP6Route *obj,
                             obj->table_coerced,
                             obj->ifindex,
                             obj->network,
-                            nm_platform_ip6_route_get_effective_metric(obj),
+                            obj->metric,
                             obj->gateway,
                             obj->pref_src,
                             obj->src,
@@ -8228,8 +8230,7 @@ nm_platform_ip6_route_cmp(const NMPlatformIP6Route *a,
         NM_CMP_DIRECT_IN6ADDR_SAME_PREFIX(&a->network, &b->network, MIN(a->plen, b->plen));
         NM_CMP_FIELD(a, b, plen);
         NM_CMP_FIELD_UNSAFE(a, b, metric_any);
-        if (!a->metric_any)
-            NM_CMP_FIELD(a, b, metric);
+        NM_CMP_FIELD(a, b, metric);
         NM_CMP_DIRECT_IN6ADDR_SAME_PREFIX(&a->src, &b->src, MIN(a->src_plen, b->src_plen));
         NM_CMP_FIELD(a, b, src_plen);
         if (cmp_type == NM_PLATFORM_IP_ROUTE_CMP_TYPE_ID) {
@@ -8254,8 +8255,7 @@ nm_platform_ip6_route_cmp(const NMPlatformIP6Route *a,
             NM_CMP_FIELD_IN6ADDR(a, b, network);
         NM_CMP_FIELD(a, b, plen);
         NM_CMP_FIELD_UNSAFE(a, b, metric_any);
-        if (!a->metric_any)
-            NM_CMP_FIELD(a, b, metric);
+        NM_CMP_FIELD(a, b, metric);
         NM_CMP_FIELD_IN6ADDR(a, b, gateway);
         NM_CMP_FIELD_IN6ADDR(a, b, pref_src);
         if (cmp_type == NM_PLATFORM_IP_ROUTE_CMP_TYPE_SEMANTICALLY) {
diff --git a/src/platform/nm-platform.h b/src/platform/nm-platform.h
index 17f3a2fd5a..df637fe03e 100644
--- a/src/platform/nm-platform.h
+++ b/src/platform/nm-platform.h
@@ -415,9 +415,9 @@ typedef union {
  * configures addresses. */
 #define NM_PLATFORM_ROUTE_METRIC_IP4_DEVICE_ROUTE ((guint32) 0u)
 
-#define __NMPlatformIPRoute_COMMON                                                       \
-    __NMPlatformObjWithIfindex_COMMON;                                                   \
-                                                                                         \
+#define __NMPlatformIPRoute_COMMON                                                        \
+    __NMPlatformObjWithIfindex_COMMON;                                                    \
+                                                                                          \
     /* The NMIPConfigSource. For routes that we receive from cache this corresponds
      * to the rtm_protocol field (and is one of the NM_IP_CONFIG_SOURCE_RTPROT_* values).
      * When adding a route, the source will be coerced to the protocol using
@@ -429,11 +429,11 @@ typedef union {
      *
      * When deleting an IPv4/IPv6 route, the rtm_protocol field must match (even
      * if it is not part of the primary key for IPv6) -- unless rtm_protocol is set
-     * to zero, in which case the first matching route (with proto ignored) is deleted. */      \
-    NMIPConfigSource rt_source;                                                          \
-                                                                                         \
-    guint8 plen;                                                                         \
-                                                                                         \
+     * to zero, in which case the first matching route (with proto ignored) is deleted. */       \
+    NMIPConfigSource rt_source;                                                           \
+                                                                                          \
+    guint8 plen;                                                                          \
+                                                                                          \
     /* RTA_METRICS:
      *
      * For IPv4 routes, these properties are part of their
@@ -444,24 +444,29 @@ typedef union {
      *
      * When deleting a route, kernel seems to ignore the RTA_METRICS properties.
      * That is a problem/bug for IPv4 because you cannot explicitly select which
-     * route to delete. Kernel just picks the first. See rh#1475642. */                                                                      \
-                                                                                         \
-    /* RTA_METRICS.RTAX_LOCK (iproute2: "lock" arguments) */                             \
-    bool lock_window : 1;                                                                \
-    bool lock_cwnd : 1;                                                                  \
-    bool lock_initcwnd : 1;                                                              \
-    bool lock_initrwnd : 1;                                                              \
-    bool lock_mtu : 1;                                                                   \
-                                                                                         \
-    /* if TRUE, the "metric" field gets ignored and can be overridden with settings from
-     * the device. This is to track routes that should be configured (e.g. from a DHCP
-     * lease), but where the actual metric is determined by NMDevice. */ \
-    bool metric_any : 1;                                                                 \
-                                                                                         \
+     * route to delete. Kernel just picks the first. See rh#1475642. */                                                                       \
+                                                                                          \
+    /* RTA_METRICS.RTAX_LOCK (iproute2: "lock" arguments) */                              \
+    bool lock_window : 1;                                                                 \
+    bool lock_cwnd : 1;                                                                   \
+    bool lock_initcwnd : 1;                                                               \
+    bool lock_initrwnd : 1;                                                               \
+    bool lock_mtu : 1;                                                                    \
+                                                                                          \
+    /* if TRUE, the "metric" field is interpreted as an offset that is added to a default
+     * metric. For example, form a DHCP lease we don't know the actually used metric, because
+     * that is determined by upper layers (the configuration). However, we have a default
+     * metric that should be used. So we set "metric_any" to %TRUE, which means to use
+     * the default metric. However, we still treat the "metric" field as an offset that
+     * will be added to the default metric. In most case, you want that "metric" is zero
+     * when setting "metric_any". */ \
+    bool metric_any : 1;                                                                  \
+                                                                                          \
     /* like "metric_any", the table is determined by other layers of the code.
-     * This field overrides "table_coerced" field. */           \
-    bool table_any : 1;                                                                  \
-                                                                                         \
+     * This field overrides "table_coerced" field. If "table_any" is true, then
+     * the "table_coerced" field is ignored (unlike for the metric). */            \
+    bool table_any : 1;                                                                   \
+                                                                                          \
     /* rtnh_flags
      *
      * Routes with rtm_flags RTM_F_CLONED are hidden by platform and
@@ -471,44 +476,46 @@ typedef union {
      * NOTE: currently we ignore all flags except RTM_F_CLONED
      * and RTNH_F_ONLINK.
      * We also may not properly consider the flags as part of the ID
-     * in route-cmp. */                                                                        \
-    unsigned r_rtm_flags;                                                                \
-                                                                                         \
-    /* RTA_METRICS.RTAX_ADVMSS (iproute2: advmss) */                                     \
-    guint32 mss;                                                                         \
-                                                                                         \
-    /* RTA_METRICS.RTAX_WINDOW (iproute2: window) */                                     \
-    guint32 window;                                                                      \
-                                                                                         \
-    /* RTA_METRICS.RTAX_CWND (iproute2: cwnd) */                                         \
-    guint32 cwnd;                                                                        \
-                                                                                         \
-    /* RTA_METRICS.RTAX_INITCWND (iproute2: initcwnd) */                                 \
-    guint32 initcwnd;                                                                    \
-                                                                                         \
-    /* RTA_METRICS.RTAX_INITRWND (iproute2: initrwnd) */                                 \
-    guint32 initrwnd;                                                                    \
-                                                                                         \
-    /* RTA_METRICS.RTAX_MTU (iproute2: mtu) */                                           \
-    guint32 mtu;                                                                         \
-                                                                                         \
-    /* RTA_PRIORITY (iproute2: metric) */                                                \
-    guint32 metric;                                                                      \
-                                                                                         \
+     * in route-cmp. */                                                                         \
+    unsigned r_rtm_flags;                                                                 \
+                                                                                          \
+    /* RTA_METRICS.RTAX_ADVMSS (iproute2: advmss) */                                      \
+    guint32 mss;                                                                          \
+                                                                                          \
+    /* RTA_METRICS.RTAX_WINDOW (iproute2: window) */                                      \
+    guint32 window;                                                                       \
+                                                                                          \
+    /* RTA_METRICS.RTAX_CWND (iproute2: cwnd) */                                          \
+    guint32 cwnd;                                                                         \
+                                                                                          \
+    /* RTA_METRICS.RTAX_INITCWND (iproute2: initcwnd) */                                  \
+    guint32 initcwnd;                                                                     \
+                                                                                          \
+    /* RTA_METRICS.RTAX_INITRWND (iproute2: initrwnd) */                                  \
+    guint32 initrwnd;                                                                     \
+                                                                                          \
+    /* RTA_METRICS.RTAX_MTU (iproute2: mtu) */                                            \
+    guint32 mtu;                                                                          \
+                                                                                          \
+    /* RTA_PRIORITY (iproute2: metric)
+     * If "metric_any" is %TRUE, then this is interpreted as an offset that will be
+     * added to a default base metric. In such cases, the offset is usually zero. */                                                    \
+    guint32 metric;                                                                       \
+                                                                                          \
     /* rtm_table, RTA_TABLE.
      *
      * This is not the original table ID. Instead, 254 (RT_TABLE_MAIN) and
      * zero (RT_TABLE_UNSPEC) are swapped, so that the default is the main
-     * table. Use nm_platform_route_table_coerce()/nm_platform_route_table_uncoerce(). */                                                             \
-    guint32 table_coerced;                                                               \
-                                                                                         \
+     * table. Use nm_platform_route_table_coerce()/nm_platform_route_table_uncoerce(). */                                                              \
+    guint32 table_coerced;                                                                \
+                                                                                          \
     /* rtm_type.
      *
      * This is not the original type, if type_coerced is 0 then
      * it means RTN_UNSPEC otherwise the type value is preserved.
-     * */                                                                         \
-    guint8 type_coerced;                                                                 \
-                                                                                         \
+     * */                                                                          \
+    guint8 type_coerced;                                                                  \
+                                                                                          \
     /*end*/
 
 typedef struct {
@@ -2078,18 +2085,18 @@ static inline guint32
 nm_platform_ip4_route_get_effective_metric(const NMPlatformIP4Route *r)
 {
     nm_assert(r);
-    nm_assert(!r->metric_any || r->metric == 0);
 
-    return r->metric_any ? NM_PLATFORM_ROUTE_METRIC_DEFAULT_IP4 : r->metric;
+    return r->metric_any ? nm_add_u32_clamped(NM_PLATFORM_ROUTE_METRIC_DEFAULT_IP4, r->metric)
+                         : r->metric;
 }
 
 static inline guint32
 nm_platform_ip6_route_get_effective_metric(const NMPlatformIP6Route *r)
 {
     nm_assert(r);
-    nm_assert(!r->metric_any || r->metric == 0);
 
-    return r->metric_any ? NM_PLATFORM_ROUTE_METRIC_DEFAULT_IP6 : r->metric;
+    return r->metric_any ? nm_add_u32_clamped(NM_PLATFORM_ROUTE_METRIC_DEFAULT_IP6, r->metric)
+                         : r->metric;
 }
 
 static inline guint32