evaluate: reset statement length context before evaluating statement

This patch consolidates ctx->stmt_len reset in stmt_evaluate() to avoid
this problem. Note that stmt_evaluate_meta() and stmt_evaluate_ct()
already reset it after the statement evaluation.

Moreover, statement dependency can be generated while evaluating a meta
and ct statement. Payload statement dependency already manually stashes
this before calling stmt_evaluate(). Add a new stmt_dependency_evaluate()
function to stash statement length context when evaluating a new statement
dependency and use it for all of the existing statement dependencies.

Florian also says:

'meta mark set vlan id map { 1 : 0x00000001, 4095 : 0x00004095 }' will
crash. Reason is that the l2 dependency generated here is errounously
expanded to a 32bit-one, so the evaluation path won't recognize this
as a L2 dependency.  Therefore, pctx->stacked_ll_count is 0 and
__expr_evaluate_payload() crashes with a null deref when
dereferencing pctx->stacked_ll[0].

nft-test.py gains a fugly hack to tolerate '!map typeof vlan id : meta mark'.
For more generic support we should find something more acceptable, e.g.

!map typeof( everything here is a key or data ) timeout ...

tests/py update and assert(pctx->stacked_ll_count) by Florian Westphal.

Fixes: edecd58755a8 ("evaluate: support shifts larger than the width of the left operand")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 25 insertions, 0 deletions

diff --git a/tests/py/any/meta.t.payload b/tests/py/any/meta.t.payload
index 16dc1211..49dd729b 100644
--- a/tests/py/any/meta.t.payload
+++ b/tests/py/any/meta.t.payload
@@ -1072,3 +1072,28 @@ ip test-ip4 input
   [ byteorder reg 1 = hton(reg 1, 8, 8) ]
   [ cmp gt reg 1 0xf3a8fd16 0x00a07719 ]
   [ immediate reg 0 accept ]
+
+# meta mark set vlan id map { 1 : 0x00000001, 4095 : 0x00004095 }
+__map%d test-ip4 b size 2
+__map%d test-ip4 0
+	element 00000100  : 00000001 0 [end]	element 0000ff0f  : 00004095 0 [end]
+ip test-ip4 input
+  [ meta load iiftype => reg 1 ]
+  [ cmp eq reg 1 0x00000001 ]
+  [ payload load 2b @ link header + 12 => reg 1 ]
+  [ cmp eq reg 1 0x00000081 ]
+  [ payload load 2b @ link header + 14 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000ff0f ) ^ 0x00000000 ]
+  [ lookup reg 1 set __map%d dreg 1 ]
+  [ meta set mark with reg 1 ]
+
+# meta mark set vlan id map @map1
+ip test-ip4 input
+  [ meta load iiftype => reg 1 ]
+  [ cmp eq reg 1 0x00000001 ]
+  [ payload load 2b @ link header + 12 => reg 1 ]
+  [ cmp eq reg 1 0x00000081 ]
+  [ payload load 2b @ link header + 14 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000ff0f ) ^ 0x00000000 ]
+  [ lookup reg 1 set map1 dreg 1 ]
+  [ meta set mark with reg 1 ]