[dpdk-dev] [PATCH] net/mlx5: fix tc rule handle assignment

[Viacheslav Ovsiienko <viacheslavo@mellanox.com>]

When tc rule is created via Netlink message application
can provide the unique rule value which can be accepted
by the kernel. Than rule is managed with this assigned
handle. It was found that kernel can reject the proposed
handle and assign its own handle value, the rule control
is lost, because application uses its initially prorosed
rule handle and knows nothing about handle been repleced.

The kernel can assign handle automatically, the application
can get the assigned handle value by specifying NLM_F_ECHO
flag in Netlink message when rule is being created. The
kernel sends back the full descriptor of rule and handle
can be retrieved from and stored by application for further
rule management.

Fixes: 57123c00c1b8 ("net/mlx5: add Linux TC flower driver for E-Switch flow")
Cc: stable@dpdk.org

Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
---
 drivers/net/mlx5/mlx5_flow_tcf.c | 97 +++++++++++++++++++++++++---------------
 1 file changed, 60 insertions(+), 37 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_flow_tcf.c b/drivers/net/mlx5/mlx5_flow_tcf.c
index cf34742..859e99a 100644
--- a/drivers/net/mlx5/mlx5_flow_tcf.c
+++ b/drivers/net/mlx5/mlx5_flow_tcf.c
@@ -2778,27 +2778,6 @@ struct pedit_parser {
 }
 
 /**
- * Brand rtnetlink buffer with unique handle.
- *
- * This handle should be unique for a given network interface to avoid
- * collisions.
- *
- * @param nlh
- *   Pointer to Netlink message.
- * @param handle
- *   Unique 32-bit handle to use.
- */
-static void
-flow_tcf_nl_brand(struct nlmsghdr *nlh, uint32_t handle)
-{
-	struct tcmsg *tcm = mnl_nlmsg_get_payload(nlh);
-
-	tcm->tcm_handle = handle;
-	DRV_LOG(DEBUG, "Netlink msg %p is branded with handle %x",
-		(void *)nlh, handle);
-}
-
-/**
  * Prepare a flow object for Linux TC flower. It calculates the maximum size of
  * memory required, allocates the memory, initializes Netlink message headers
  * and set unique TC message handle.
@@ -2888,20 +2867,6 @@ struct pedit_parser {
 		dev_flow->tcf.tunnel->type = FLOW_TCF_TUNACT_VXLAN_DECAP;
 	else if (action_flags & MLX5_FLOW_ACTION_VXLAN_ENCAP)
 		dev_flow->tcf.tunnel->type = FLOW_TCF_TUNACT_VXLAN_ENCAP;
-	/*
-	 * Generate a reasonably unique handle based on the address of the
-	 * target buffer.
-	 *
-	 * This is straightforward on 32-bit systems where the flow pointer can
-	 * be used directly. Otherwise, its least significant part is taken
-	 * after shifting it by the previous power of two of the pointed buffer
-	 * size.
-	 */
-	if (sizeof(dev_flow) <= 4)
-		flow_tcf_nl_brand(nlh, (uintptr_t)dev_flow);
-	else
-		flow_tcf_nl_brand(nlh, (uintptr_t)dev_flow >>
-				       rte_log2_u32(rte_align32prevpow2(size)));
 	return dev_flow;
 }
 
@@ -5593,6 +5558,7 @@ struct tcf_nlcb_query {
 	struct mlx5_flow_tcf_context *ctx = priv->tcf_context;
 	struct mlx5_flow *dev_flow;
 	struct nlmsghdr *nlh;
+	struct tcmsg *tcm;
 
 	if (!flow)
 		return;
@@ -5613,11 +5579,54 @@ struct tcf_nlcb_query {
 				dev_flow);
 			dev_flow->tcf.tunnel->vtep = NULL;
 		}
+		/* Cleanup the rule handle value. */
+		tcm = mnl_nlmsg_get_payload(nlh);
+		tcm->tcm_handle = 0;
 		dev_flow->tcf.applied = 0;
 	}
 }
 
 /**
+ * Fetch the applied rule handle. This is callback routine called by
+ * libmnl mnl_cb_run() in loop for every message in received packet.
+ * When the NLM_F_ECHO flag i sspecified the kernel sends the created
+ * rule descriptor back to the application and we can retrieve the
+ * actual rule handle from updated descriptor.
+ *
+ * @param[in] nlh
+ *   Pointer to reply header.
+ * @param[in, out] arg
+ *   Context pointer for this callback.
+ *
+ * @return
+ *   A positive, nonzero value on success (required by libmnl
+ *   to continue messages processing).
+ */
+static int
+flow_tcf_collect_apply_cb(const struct nlmsghdr *nlh, void *arg)
+{
+	struct nlmsghdr *nlhrq = arg;
+	struct tcmsg *tcmrq = mnl_nlmsg_get_payload(nlhrq);
+	struct tcmsg *tcm = mnl_nlmsg_get_payload(nlh);
+	struct nlattr *na;
+
+	if (nlh->nlmsg_type != RTM_NEWTFILTER ||
+	    nlh->nlmsg_seq != nlhrq->nlmsg_seq)
+		return 1;
+	mnl_attr_for_each(na, nlh, sizeof(*tcm)) {
+		switch (mnl_attr_get_type(na)) {
+		case TCA_KIND:
+			if (strcmp(mnl_attr_get_payload(na), "flower")) {
+				/* Not flower filter, drop entire message. */
+				return 1;
+			}
+			tcmrq->tcm_handle = tcm->tcm_handle;
+			return 1;
+		}
+	}
+	return 1;
+}
+/**
  * Apply flow to E-Switch by sending Netlink message.
  *
  * @param[in] dev
@@ -5638,6 +5647,8 @@ struct tcf_nlcb_query {
 	struct mlx5_flow_tcf_context *ctx = priv->tcf_context;
 	struct mlx5_flow *dev_flow;
 	struct nlmsghdr *nlh;
+	struct tcmsg *tcm;
+	int ret;
 
 	dev_flow = LIST_FIRST(&flow->dev_flows);
 	/* E-Switch flow can't be expanded. */
@@ -5646,7 +5657,11 @@ struct tcf_nlcb_query {
 		return 0;
 	nlh = dev_flow->tcf.nlh;
 	nlh->nlmsg_type = RTM_NEWTFILTER;
-	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
+	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE |
+			   NLM_F_EXCL | NLM_F_ECHO;
+	tcm = mnl_nlmsg_get_payload(nlh);
+	/* Allow kernel to assign handle on its own. */
+	tcm->tcm_handle = 0;
 	if (dev_flow->tcf.tunnel) {
 		/*
 		 * Replace the interface index, target for
@@ -5667,7 +5682,15 @@ struct tcf_nlcb_query {
 		*dev_flow->tcf.tunnel->ifindex_ptr =
 			dev_flow->tcf.tunnel->vtep->ifindex;
 	}
-	if (!flow_tcf_nl_ack(ctx, nlh, NULL, NULL)) {
+	ret = flow_tcf_nl_ack(ctx, nlh, flow_tcf_collect_apply_cb, nlh);
+	if (!ret) {
+		if (!tcm->tcm_handle) {
+			flow_tcf_remove(dev, flow);
+			return rte_flow_error_set
+				(error, ENOENT,
+				 RTE_FLOW_ERROR_TYPE_UNSPECIFIED, NULL,
+				 "netlink: rule zero handle returned");
+		}
 		dev_flow->tcf.applied = 1;
 		if (*dev_flow->tcf.ptc_flags & TCA_CLS_FLAGS_SKIP_SW)
 			return 0;
-- 
1.8.3.1