[RFC PATCH nft] payload: Don't kill dependency for proto_th

[Xiao Liang <shaw.leon@gmail.com>]

Since proto_th carries no information about the proto number, we need to
preserve the L4 protocol expression.

For example, if "meta l4proto 91 @th,0,16 0" is simplified to
"th sport 0", the information of protocol number is lost. This patch
changes it to "meta l4proto 91 th sport 0".

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
---

Technically, if port is not defined for the L4 protocol, it's better to
keep "@th,0,16" as raw payload expressions rather than "th sport". But
it's not easy to figure out the context.

---
 src/payload.c                     |  1 +
 tests/py/any/rawpayload.t         |  1 +
 tests/py/any/rawpayload.t.json    | 31 +++++++++++++++++++++++++++++++
 tests/py/any/rawpayload.t.payload |  8 ++++++++
 4 files changed, 41 insertions(+)

diff --git a/src/payload.c b/src/payload.c
index f8b192b5..a039e242 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -920,6 +920,7 @@ void payload_dependency_kill(struct payload_dep_ctx *ctx, struct expr *expr,
 			     unsigned int family)
 {
 	if (expr->payload.desc != &proto_unknown &&
+	    expr->payload.desc != &proto_th &&
 	    payload_dependency_exists(ctx, expr->payload.base) &&
 	    payload_may_dependency_kill(ctx, family, expr))
 		payload_dependency_release(ctx, expr->payload.base);
diff --git a/tests/py/any/rawpayload.t b/tests/py/any/rawpayload.t
index 745b4a61..4ef53f82 100644
--- a/tests/py/any/rawpayload.t
+++ b/tests/py/any/rawpayload.t
@@ -21,6 +21,7 @@ meta l4proto tcp @th,16,16 { 22, 23, 80};ok;tcp dport { 22, 23, 80}
 @ll,0,128 0xfedcba987654321001234567890abcde;ok
 
 meta l4proto 91 @th,400,16 0x0 accept;ok
+meta l4proto 91 @th,0,16 0x0 accept;ok;meta l4proto 91 th sport 0 accept
 
 @ih,32,32 0x14000000;ok
 @ih,58,6 set 0 @ih,86,6 set 0 @ih,170,22 set 0;ok;@ih,58,6 set 0x0 @ih,86,6 set 0x0 @ih,170,22 set 0x0
diff --git a/tests/py/any/rawpayload.t.json b/tests/py/any/rawpayload.t.json
index 4a06c598..2d3c7904 100644
--- a/tests/py/any/rawpayload.t.json
+++ b/tests/py/any/rawpayload.t.json
@@ -187,6 +187,37 @@
     }
 ]
 
+# meta l4proto 91 @th,0,16 0x0 accept
+[
+    {
+        "match": {
+            "left": {
+                "meta": {
+                    "key": "l4proto"
+                }
+            },
+            "op": "==",
+            "right": 91
+        }
+    },
+    {
+        "match": {
+            "left": {
+                "payload": {
+                    "field": "sport",
+                    "protocol": "th"
+                }
+            },
+            "op": "==",
+            "right": 0
+        }
+    },
+    {
+        "accept": null
+    }
+]
+
+
 # @ih,32,32 0x14000000
 [
     {
diff --git a/tests/py/any/rawpayload.t.payload b/tests/py/any/rawpayload.t.payload
index 8984eef6..c093d5d8 100644
--- a/tests/py/any/rawpayload.t.payload
+++ b/tests/py/any/rawpayload.t.payload
@@ -56,6 +56,14 @@ inet test-inet input
   [ cmp eq reg 1 0x00000000 ]
   [ immediate reg 0 accept ]
 
+# meta l4proto 91 @th,0,16 0x0 accept
+inet test-inet input
+  [ meta load l4proto => reg 1 ]
+  [ cmp eq reg 1 0x0000005b ]
+  [ payload load 2b @ transport header + 0 => reg 1 ]
+  [ cmp eq reg 1 0x00000000 ]
+  [ immediate reg 0 accept ]
+
 # @ih,32,32 0x14000000
 inet test-inet input
   [ payload load 4b @ inner header + 4 => reg 1 ]
-- 
2.48.1