tunmap: ensure nft table is removed on program exit

Make the nft table owned by the osmo-upf process, so that any kind of
graceful or ungraceful exit will drop all tunmap rules implicitly.

Related: SYS#6327 SYS#6264
Change-Id: Ia26bb295849905ccfeaec801d7b187bf85f21366

src/osmo-upf/upf_nft.c

@@ -32,7 +32,7 @@
 
 static char *upf_nft_ruleset_table_create(void *ctx, const char *table_name)
 {
-	return talloc_asprintf(ctx, "add table inet %s\n", table_name);
+	return talloc_asprintf(ctx, "add table inet %s { flags owner; };\n", table_name);
 }
 
 static char *upf_nft_ruleset_vmap_init(void *ctx, const char *table_name, int priority_pre, int priority_post)

tests/nft-rule.vty

@@ -4,7 +4,7 @@ OsmoUPF(config)# tunmap
 
 OsmoUPF(config-tunmap)# show nft-rule tunmap example
 % init verdict map:
-add table inet osmo-upf
+add table inet osmo-upf { flags owner; };
 
 add chain inet osmo-upf pre { type filter hook prerouting priority -300; policy accept; };
 add chain inet osmo-upf post { type filter hook postrouting priority 400; policy accept; };