fib: allow to check if route exists in maps

f686a17eafa0 ("fib: Support existence check") adds EXPR_F_BOOLEAN as a
workaround to infer from the rhs of the relational expression if the fib
lookup wants to check for a specific output interface or, instead,
simply check for existence. This, however, does not work with maps.

The NFT_FIB_F_PRESENT flag can be used both with NFT_FIB_RESULT_OIF and
NFT_FIB_RESULT_OFINAME, my understanding is that they serve the same
purpose which is to check if a route exists, so they are redundant.

Add a 'check' fib result to check for routes while still keeping the
inference workaround for backward compatibility, but prefer the new
syntax in the listing.

Update man nft(8) and tests/py.

Fixes: f686a17eafa0 ("fib: Support existence check")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 46 insertions, 9 deletions

diff --git a/tests/py/inet/fib.t b/tests/py/inet/fib.t
index dbe45d95..f9c03b3a 100644
--- a/tests/py/inet/fib.t
+++ b/tests/py/inet/fib.t
@@ -13,5 +13,7 @@ fib daddr . iif type local;ok
 fib daddr . iif type vmap { blackhole : drop, prohibit : drop, unicast : accept };ok
 fib daddr . oif type local;fail
 
-fib daddr oif exists;ok
-fib daddr oif missing;ok
+fib daddr check missing;ok
+fib daddr oif exists;ok;fib daddr check exists
+
+fib daddr check vmap { missing : drop, exists : accept };ok
diff --git a/tests/py/inet/fib.t.json b/tests/py/inet/fib.t.json
index c2989156..c2e9d454 100644
--- a/tests/py/inet/fib.t.json
+++ b/tests/py/inet/fib.t.json
@@ -103,7 +103,7 @@
                     "flags": [
                         "daddr"
                     ],
-                    "result": "oif"
+                    "result": "check"
                 }
             },
 	    "op": "==",
@@ -112,7 +112,7 @@
     }
 ]
 
-# fib daddr oif missing
+# fib daddr check missing
 [
     {
         "match": {
@@ -121,7 +121,7 @@
                     "flags": [
                         "daddr"
                     ],
-                    "result": "oif"
+                    "result": "check"
                 }
             },
 	    "op": "==",
@@ -130,3 +130,32 @@
     }
 ]
 
+# fib daddr check vmap { missing : drop, exists : accept }
+[
+    {
+        "vmap": {
+            "data": {
+                "set": [
+                    [
+                        false,
+                        {
+                            "drop": null
+                        }
+                    ],
+                    [
+                        true,
+                        {
+                            "accept": null
+                        }
+                    ]
+                ]
+            },
+            "key": {
+                "fib": {
+                    "flags": "daddr",
+                    "result": "check"
+                }
+            }
+        }
+    }
+]
diff --git a/tests/py/inet/fib.t.json.output b/tests/py/inet/fib.t.json.output
index e21f1e72..e8d01669 100644
--- a/tests/py/inet/fib.t.json.output
+++ b/tests/py/inet/fib.t.json.output
@@ -44,7 +44,7 @@
             "left": {
                 "fib": {
                     "flags": "daddr",
-                    "result": "oif"
+                    "result": "check"
                 }
             },
             "op": "==",
@@ -53,14 +53,14 @@
     }
 ]
 
-# fib daddr oif missing
+# fib daddr check missing
 [
     {
         "match": {
             "left": {
                 "fib": {
                     "flags": "daddr",
-                    "result": "oif"
+                    "result": "check"
                 }
             },
             "op": "==",
diff --git a/tests/py/inet/fib.t.payload b/tests/py/inet/fib.t.payload
index 050857d9..e09a260c 100644
--- a/tests/py/inet/fib.t.payload
+++ b/tests/py/inet/fib.t.payload
@@ -26,7 +26,13 @@ ip test-ip prerouting
   [ fib daddr oif present => reg 1 ]
   [ cmp eq reg 1 0x00000001 ]
 
-# fib daddr oif missing
+# fib daddr check missing
 ip test-ip prerouting
   [ fib daddr oif present => reg 1 ]
   [ cmp eq reg 1 0x00000000 ]
+
+# fib daddr check vmap { missing : drop, exists : accept }
+        element 00000000  : drop 0 [end]        element 00000001  : accept 0 [end]
+ip test-ip prerouting
+  [ fib daddr oif present => reg 1 ]
+  [ lookup reg 1 set __map%d dreg 0 ]