[PATCH net v2 2/3] net: dsa: motorcomm: Resolve the flower action list to one ACL verdict

[David Yang <mmyangfl@gmail.com>]

The hardware resolves one forward decision per ACL rule, but the
translation accumulated every action, so a later action silently changed
the verdict of the ones before it: an `action drop action trap` filter
with skip_sw trapped packets to the CPU instead of dropping them.

Resolve the list against its first terminal action. Consecutive
redirects merge into the destination port mask, since a flow action
entry carries no mirred control verdict to tell whether software would
have continued; an action asking for a second decision is rejected when
skip_sw is set and left to the software path otherwise.

Fixes: 8eb9e7520b17 ("net: dsa: yt921x: Add ACL support")
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/dsa/motorcomm/tc.c | 72 +++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 35 deletions(-)

diff --git a/drivers/net/dsa/motorcomm/tc.c b/drivers/net/dsa/motorcomm/tc.c
index 8835907366bf..5d2db04f3385 100644
--- a/drivers/net/dsa/motorcomm/tc.c
+++ b/drivers/net/dsa/motorcomm/tc.c
@@ -1030,55 +1030,54 @@ yt921x_acl_rule_ext_parse_flow_action(struct yt921x_acl_rule_ext *ruleext,
 	const struct flow_rule *rule = flow_cls_offload_flow_rule(cls);
 	const struct flow_action *flow_action = &rule->action;
 	struct netlink_ext_ack *extack = cls->common.extack;
-	enum flow_action_id redir_act = NUM_FLOW_ACTIONS;
 	const struct flow_action_entry *act;
 	u32 *action = ruleext->r.action;
 	bool seen_priority = false;
 	const char *reason = NULL;
 	bool seen_police = false;
+	bool terminal = false;
+	bool redir = false;
 	unsigned int i;
 	int res;
 
 	memset(action, 0, 3 * sizeof(*action));
-	flow_action_for_each(i, act, flow_action)
+	flow_action_for_each(i, act, flow_action) {
+		/* Only another redirect, or a drop, can follow a redirect: a
+		 * drop is an empty destination set, so the software verdict is
+		 * the same whichever control the redirect carries.
+		 */
+		if (redir && act->id != FLOW_ACTION_REDIRECT &&
+		    act->id != FLOW_ACTION_DROP) {
+			reason = "Action after redirect";
+			goto fallback;
+		}
+
 		switch (act->id) {
 		case FLOW_ACTION_ACCEPT:
+			action[2] |= YT921X_ACL_ACTc_FWD_EN |
+				     YT921X_ACL_ACTc_FWD_FWD;
+			terminal = true;
+			break;
 		case FLOW_ACTION_DROP:
-		case FLOW_ACTION_REDIRECT:
-			if (redir_act != NUM_FLOW_ACTIONS &&
-			    redir_act != act->id) {
-				reason = "Different redirect actions";
+			action[2] |= YT921X_ACL_ACTc_FWD_EN |
+				     YT921X_ACL_ACTc_FWD_REDIR;
+			terminal = true;
+			break;
+		case FLOW_ACTION_REDIRECT: {
+			struct dsa_port *to_dp;
+
+			to_dp = dsa_port_from_netdev(act->dev);
+			if (IS_ERR(to_dp) || to_dp->ds != &priv->ds) {
+				reason = "Redirect to non-local port";
 				goto fallback;
 			}
-			redir_act = act->id;
-
-			switch (act->id) {
-			case FLOW_ACTION_ACCEPT:
-				action[2] |= YT921X_ACL_ACTc_FWD_EN |
-					     YT921X_ACL_ACTc_FWD_FWD;
-				break;
-			case FLOW_ACTION_DROP:
-				action[2] |= YT921X_ACL_ACTc_FWD_EN |
-					     YT921X_ACL_ACTc_FWD_REDIR;
-				break;
-			case FLOW_ACTION_REDIRECT: {
-				struct dsa_port *to_dp;
 
-				to_dp = dsa_port_from_netdev(act->dev);
-				if (IS_ERR(to_dp) || to_dp->ds != &priv->ds) {
-					reason = "Redirect to non-local port";
-					goto fallback;
-				}
-
-				action[2] |= YT921X_ACL_ACTc_FWD_EN |
-					     YT921X_ACL_ACTc_FWD_REDIR |
-					     YT921X_ACL_ACTc_FWD_REDIR_DPORTn(to_dp->index);
-				break;
-			}
-			default:
-				break;
-			}
+			action[2] |= YT921X_ACL_ACTc_FWD_EN |
+				     YT921X_ACL_ACTc_FWD_REDIR |
+				     YT921X_ACL_ACTc_FWD_REDIR_DPORTn(to_dp->index);
+			redir = true;
 			break;
+		}
 		case FLOW_ACTION_PRIORITY:
 			if (seen_priority) {
 				action[0] &= ~YT921X_ACL_ACTa_PRIO_EN;
@@ -1132,15 +1131,18 @@ yt921x_acl_rule_ext_parse_flow_action(struct yt921x_acl_rule_ext *ruleext,
 			}
 			fallthrough;
 		case FLOW_ACTION_TRAP:
-			redir_act = FLOW_ACTION_TRAP;
-
 			action[2] &= ~YT921X_ACL_ACTc_FWD_REDIR_DPORTS_M &
 				     ~YT921X_ACL_ACTc_FWD_M;
 			action[2] |= YT921X_ACL_ACTc_FWD_EN |
 				     YT921X_ACL_ACTc_FWD_TRAP;
+			terminal = true;
 			break;
 		}
 
+		if (terminal)
+			break;
+	}
+
 	ruleext->r.sw_assisted = !cls->common.skip_sw;
 	return 0;
 }
-- 
2.53.0