[PATCH nft 2/2] evaluate: improve error reporting in tproxy with inet family

[Pablo Neira Ayuso <pablo@netfilter.org>]

 # nft add rule inet filter divert ip daddr 0.0.0.0/0 meta l4proto tcp tproxy to :2000
 Error: conflicting protocols specified: ip vs. unknown. You must specify ip or ip6 family in tproxy statement
 add rule inet filter divert ip daddr 0.0.0.0/0 meta l4proto tcp tproxy to :2000
                             ~~~~~~~~                            ^^^^^^^^^^^^^^^

instead of:

 # nft add rule inet filter divert ip daddr 0.0.0.0/0 meta l4proto tcp tproxy to :2000
 Error: Conflicting network layer protocols.
 add rule inet filter divert ip daddr 0.0.0.0/0 meta l4proto tcp tproxy to :2000
                                                                 ^^^^^^^^^^^^^^^

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1310
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/evaluate.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/evaluate.c b/src/evaluate.c
index 94377da99335..3a3f2468c826 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -2606,8 +2606,11 @@ static int stmt_evaluate_tproxy(struct eval_ctx *ctx, struct stmt *stmt)
 		/* this prevents us from rules like
 		 * ip protocol tcp tproxy ip6 to [dead::beef]
 		 */
-		return stmt_error(ctx, stmt,
-				  "Conflicting network layer protocols.");
+		return stmt_binary_error(ctx, stmt,
+					 &ctx->pctx.protocol[PROTO_BASE_NETWORK_HDR],
+					 "conflicting protocols specified: %s vs. %s. You must specify ip or ip6 family in tproxy statement",
+					 ctx->pctx.protocol[PROTO_BASE_NETWORK_HDR].desc->name,
+					 family2str(stmt->tproxy.family));
 
 	if (stmt->tproxy.addr != NULL) {
 		if (stmt->tproxy.addr->etype == EXPR_RANGE)
-- 
2.11.0