netlink_linearize: skip set element expression in map statement key

This fix is similar to 22d201010919 ("netlink_linearize: skip set element
expression in set statement key") to fix map statement.

netlink_gen_map_stmt() relies on the map key, that is expressed as a set
element. Use the set element key instead to skip the set element wrap,
otherwise get_register() abort execution:

  nft: netlink_linearize.c:650: netlink_gen_expr: Assertion `dreg < ctx->reg_low' failed.

This includes JSON support to make this feature complete and it updates
tests/shell to cover for this support.

Reported-by: Luci Stanescu <luci@cnix.ro>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/py/ip6/sets.t.json b/tests/py/ip6/sets.t.json
index 948c1f16..2029d2b5 100644
--- a/tests/py/ip6/sets.t.json
+++ b/tests/py/ip6/sets.t.json
@@ -116,3 +116,35 @@
         }
     }
 ]
+
+# add @map1 { ip6 saddr . ip6 daddr : meta mark }
+[
+    {
+        "map": {
+            "data": {
+                "meta": {
+                    "key": "mark"
+                }
+            },
+            "elem": {
+                "concat": [
+                    {
+                        "payload": {
+                            "field": "saddr",
+                            "protocol": "ip6"
+                        }
+                    },
+                    {
+                        "payload": {
+                            "field": "daddr",
+                            "protocol": "ip6"
+                        }
+                    }
+                ]
+            },
+            "map": "@map1",
+            "op": "add"
+        }
+    }
+]
+