nftables/0024-evaluate-place-byteorder-conversion-before-rshift-in.patch

From 2d5e3d1d7241a86d1555b3edfb020f20fc95748d Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Fri, 17 Jul 2026 11:08:18 +0200
Subject: [PATCH] evaluate: place byteorder conversion before rshift in payload
 expressions

JIRA: https://issues.redhat.com/browse/RHEL-190549
Upstream Status: nftables commit cb9b72a43c5684379c027908d9f332170bf8dd15

commit cb9b72a43c5684379c027908d9f332170bf8dd15
Author: Pablo Neira Ayuso <pablo@netfilter.org>
Date:   Sun Nov 5 21:54:25 2023 +0100

    evaluate: place byteorder conversion before rshift in payload expressions

    Use the key from the evaluation context to perform the byteorder
    conversion in case that this expression is used for lookups and updates
    on explicit sets.

     # nft --debug=netlink add rule ip6 t output ip6 dscp @mapv6
     ip6 t output
      [ payload load 2b @ network header + 0 => reg 1 ]
      [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
      [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]   <-------------- this was missing!
      [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
      [ lookup reg 1 set mapv6 ]

    Also with set statements (updates from packet path):

     # nft --debug=netlink add rule ip6 t output update @mapv6 { ip6 dscp }
     ip6 t output
      [ payload load 2b @ network header + 0 => reg 1 ]
      [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
      [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]   <------------- also here!
      [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
      [ dynset update reg_key 1 set mapv6 ]

    Simple matches on values and implicit sets rely on the binary transfer
    mechanism to propagate the shift to the constant, no explicit byteorder
    is required in such case.

    Fixes: 668c18f67203 ("evaluate: place byteorder conversion before rshift in payload statement")
    Reported-by: Florian Westphal <fw@strlen.de>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Signed-off-by: Phil Sutter <psutter@redhat.com>
---
 src/evaluate.c                  | 10 +++++++-
 tests/py/ip6/ip6.t              |  4 ++++
 tests/py/ip6/ip6.t.json         | 42 +++++++++++++++++++++++++++++++++
 tests/py/ip6/ip6.t.payload.inet | 21 +++++++++++++++++
 tests/py/ip6/ip6.t.payload.ip6  | 17 +++++++++++++
 5 files changed, 93 insertions(+), 1 deletion(-)

diff --git a/src/evaluate.c b/src/evaluate.c
index 1850043..303e36c 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -545,7 +545,8 @@ static void expr_evaluate_bits(struct eval_ctx *ctx, struct expr **exprp)
 	and->len	= masklen;
 
 	if (shift) {
-		if (ctx->stmt_len > 0 && div_round_up(masklen, BITS_PER_BYTE) > 1) {
+		if ((ctx->ectx.key || ctx->stmt_len > 0) &&
+		    div_round_up(masklen, BITS_PER_BYTE) > 1) {
 			int op = byteorder_conversion_op(expr, BYTEORDER_HOST_ENDIAN);
 			and = unary_expr_alloc(&expr->location, op, and);
 			and->len = masklen;
@@ -574,6 +575,7 @@ static void expr_evaluate_bits(struct eval_ctx *ctx, struct expr **exprp)
 
 static int __expr_evaluate_exthdr(struct eval_ctx *ctx, struct expr **exprp)
 {
+	const struct expr *key = ctx->ectx.key;
 	struct expr *expr = *exprp;
 
 	if (expr->exthdr.flags & NFT_EXTHDR_F_PRESENT)
@@ -582,6 +584,8 @@ static int __expr_evaluate_exthdr(struct eval_ctx *ctx, struct expr **exprp)
 	if (expr_evaluate_primary(ctx, exprp) < 0)
 		return -1;
 
+	ctx->ectx.key = key;
+
 	if (expr->exthdr.offset % BITS_PER_BYTE != 0 ||
 	    expr->len % BITS_PER_BYTE != 0)
 		expr_evaluate_bits(ctx, exprp);
@@ -878,6 +882,7 @@ static bool payload_needs_adjustment(const struct expr *expr)
 
 static int expr_evaluate_payload(struct eval_ctx *ctx, struct expr **exprp)
 {
+	const struct expr *key = ctx->ectx.key;
 	struct expr *expr = *exprp;
 
 	if (expr->payload.evaluated)
@@ -889,6 +894,8 @@ static int expr_evaluate_payload(struct eval_ctx *ctx, struct expr **exprp)
 	if (expr_evaluate_primary(ctx, exprp) < 0)
 		return -1;
 
+	ctx->ectx.key = key;
+
 	if (payload_needs_adjustment(expr))
 		expr_evaluate_bits(ctx, exprp);
 
@@ -1508,6 +1515,7 @@ static int expr_evaluate_concat(struct eval_ctx *ctx, struct expr **expr)
 		}
 
 		__expr_set_context(&ctx->ectx, tmp, bo, dsize, 0);
+		ctx->ectx.key = i;
 
 		if (list_member_evaluate(ctx, &i) < 0)
 			return -1;
diff --git a/tests/py/ip6/ip6.t b/tests/py/ip6/ip6.t
index 60ea223..430dd57 100644
--- a/tests/py/ip6/ip6.t
+++ b/tests/py/ip6/ip6.t
@@ -21,6 +21,10 @@ ip6 dscp vmap { 0x04 : accept, 0x3f : continue } counter;ok
 meta mark set ip6 dscp map @map1;ok
 !map2 type dscp . ipv6_addr : mark;ok
 meta mark set ip6 dscp . ip6 daddr map @map2;ok
+!map3 type dscp : mark;ok
+ip6 dscp @map3;ok
+!map4 type dscp . ipv6_addr : mark;ok
+ip6 dscp . ip6 daddr @map4;ok
 
 ip6 flowlabel 22;ok
 ip6 flowlabel != 233;ok
diff --git a/tests/py/ip6/ip6.t.json b/tests/py/ip6/ip6.t.json
index 5411190..49e5a2d 100644
--- a/tests/py/ip6/ip6.t.json
+++ b/tests/py/ip6/ip6.t.json
@@ -193,6 +193,48 @@
     }
 ]
 
+# ip6 dscp @map3
+[
+    {
+        "match": {
+            "left": {
+                "payload": {
+                    "field": "dscp",
+                    "protocol": "ip6"
+                }
+            },
+            "op": "==",
+            "right": "@map3"
+        }
+    }
+]
+
+# ip6 dscp . ip6 daddr @map4
+[
+    {
+        "match": {
+            "left": {
+                "concat": [
+                    {
+                        "payload": {
+                            "field": "dscp",
+                            "protocol": "ip6"
+                        }
+                    },
+                    {
+                        "payload": {
+                            "field": "daddr",
+                            "protocol": "ip6"
+                        }
+                    }
+                ]
+            },
+            "op": "==",
+            "right": "@map4"
+        }
+    }
+]
+
 # ip6 flowlabel 22
 [
     {
diff --git a/tests/py/ip6/ip6.t.payload.inet b/tests/py/ip6/ip6.t.payload.inet
index 214a0ed..dbb430a 100644
--- a/tests/py/ip6/ip6.t.payload.inet
+++ b/tests/py/ip6/ip6.t.payload.inet
@@ -76,6 +76,27 @@ inet test-inet input
   [ lookup reg 1 set map2 dreg 1 ]
   [ meta set mark with reg 1 ]
 
+# ip6 dscp @map3
+inet test-inet input
+  [ meta load nfproto => reg 1 ]
+  [ cmp eq reg 1 0x0000000a ]
+  [ payload load 2b @ network header + 0 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
+  [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]
+  [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
+  [ lookup reg 1 set map3 ]
+
+# ip6 dscp . ip6 daddr @map4
+inet test-inet input
+  [ meta load nfproto => reg 1 ]
+  [ cmp eq reg 1 0x0000000a ]
+  [ payload load 2b @ network header + 0 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
+  [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]
+  [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
+  [ payload load 16b @ network header + 24 => reg 9 ]
+  [ lookup reg 1 set map4 ]
+
 # ip6 flowlabel 22
 inet test-inet input
   [ meta load nfproto => reg 1 ]
diff --git a/tests/py/ip6/ip6.t.payload.ip6 b/tests/py/ip6/ip6.t.payload.ip6
index 428b8ea..b128923 100644
--- a/tests/py/ip6/ip6.t.payload.ip6
+++ b/tests/py/ip6/ip6.t.payload.ip6
@@ -60,6 +60,23 @@ ip6 test-ip6 input
   [ lookup reg 1 set map2 dreg 1 ]
   [ meta set mark with reg 1 ]
 
+# ip6 dscp @map3
+ip6 test-ip6 input
+  [ payload load 2b @ network header + 0 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
+  [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]
+  [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
+  [ lookup reg 1 set map3 ]
+
+# ip6 dscp . ip6 daddr @map4
+ip6 test-ip6 input
+  [ payload load 2b @ network header + 0 => reg 1 ]
+  [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ]
+  [ byteorder reg 1 = ntoh(reg 1, 2, 2) ]
+  [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ]
+  [ payload load 16b @ network header + 24 => reg 9 ]
+  [ lookup reg 1 set map4 ]
+
 # ip6 flowlabel 22
 ip6 test-ip6 input
   [ payload load 3b @ network header + 1 => reg 1 ]