[PATCH v1] net/tap: fix isolation mode toggling

[Ophir Munk <ophirmu@mellanox.com>]

Running testpmd command "flow isolae <port> 0" (i.e. disabling flow
isolation) followed by command "flow isolate <port> 1" (i.e. enabling
flow isolation) may result in a TAP error:
PMD: Kernel refused TC filter rule creation (17): File exists

Root cause analysis: when disabling flow isolation we keep the local
rule to redirect packets on TX (TAP_REMOTE_TX index) while we add it
again when enabling flow isolation. As a result this rule is added
two times in a raw which results in "File exists" error.
The fix is to identify the "File exists" error and silently ignore it.

Another issue occurs when enabling isolation mode several times in a
raw in which case the same tc rules are added consecutively and
rte_flow structs are added to a linked list before removing the
previous rte_flow structs.
The fix is to act upon isolation mode command only when there is a
change from "0" to "1" (or vice versa).

Fixes: f503d2694825 ("net/tap: support flow API isolated mode")
Cc: stable@dpdk.org

Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
---
 drivers/net/tap/tap_flow.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/drivers/net/tap/tap_flow.c b/drivers/net/tap/tap_flow.c
index aab9eef..91f15f6 100644
--- a/drivers/net/tap/tap_flow.c
+++ b/drivers/net/tap/tap_flow.c
@@ -1568,10 +1568,10 @@ tap_flow_isolate(struct rte_eth_dev *dev,
 {
 	struct pmd_internals *pmd = dev->data->dev_private;
 
-	if (set)
-		pmd->flow_isolate = 1;
-	else
-		pmd->flow_isolate = 0;
+	/* if already in the right isolation mode - nothing to do */
+	if ((!!set ^ pmd->flow_isolate) == 0)
+		return 0;
+	pmd->flow_isolate = !!set;
 	/*
 	 * If netdevice is there, setup appropriate flow rules immediately.
 	 * Otherwise it will be set when bringing up the netdevice (tun_alloc).
@@ -1579,21 +1579,30 @@ tap_flow_isolate(struct rte_eth_dev *dev,
 	if (!pmd->rxq[0].fd)
 		return 0;
 	if (set) {
-		struct rte_flow *flow;
+		struct rte_flow *remote_flow;
 
-		while (1) {
-			flow = LIST_FIRST(&pmd->implicit_flows);
-			if (!flow)
+		while (!LIST_EMPTY(&pmd->implicit_flows)) {
+			remote_flow = LIST_FIRST(&pmd->implicit_flows);
+			if (!remote_flow)
 				break;
 			/*
 			 * Remove all implicit rules on the remote.
 			 * Keep the local rule to redirect packets on TX.
 			 * Keep also the last implicit local rule: ISOLATE.
 			 */
-			if (flow->msg.t.tcm_ifindex == pmd->if_index)
-				break;
-			if (tap_flow_destroy_pmd(pmd, flow, NULL) < 0)
-				goto error;
+			if (remote_flow->msg.t.tcm_ifindex != pmd->if_index) {
+				/*
+				 * remove TC from kernel and
+				 * remote_flow from list
+				 */
+				if (tap_flow_destroy_pmd(pmd, remote_flow,
+						NULL) < 0)
+					goto error;
+			} else {
+				/* remove remote_flow from list */
+				LIST_REMOVE(remote_flow, next);
+				rte_free(remote_flow);
+			}
 		}
 		/* Switch the TC rule according to pmd->flow_isolate */
 		if (tap_flow_implicit_create(pmd, TAP_ISOLATE) == -1)
@@ -1739,8 +1748,8 @@ int tap_flow_implicit_create(struct pmd_internals *pmd,
 	}
 	err = tap_nl_recv_ack(pmd->nlsk_fd);
 	if (err < 0) {
-		/* Silently ignore re-entering remote promiscuous rule */
-		if (errno == EEXIST && idx == TAP_REMOTE_PROMISC)
+		/* Silently ignore re-entering existing rule */
+		if (errno == EEXIST)
 			goto success;
 		TAP_LOG(ERR,
 			"Kernel refused TC filter rule creation (%d): %s",
-- 
2.7.4