[PATCH dpdk v4 4/4] net/tap: configure link carrier

[Robin Jarry <rjarry@redhat.com>]

In order for net_tap interfaces to be used in linux bonds, they need to
report a carrier.

After at last one RX queue has been configured, force the carrier on
with ioctl(TUNSETCARRIER) (there is no netlink equivalent for this).

Also do the same after the device has been moved to another netns.

TUNSETCARRIER support was added in Linux 5.0. Only enable carrier set if
this ioctl number is defined.

Signed-off-by: Robin Jarry <rjarry@redhat.com>
---
 drivers/net/tap/rte_eth_tap.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 7869183c0ffe..730f1859bd28 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -1392,6 +1392,22 @@ tap_mac_set(struct rte_eth_dev *dev, struct rte_ether_addr *mac_addr)
 	return 0;
 }
 
+static int tap_carrier_set(struct pmd_internals *pmd, int carrier)
+{
+#ifdef TUNSETCARRIER
+	int ret = ioctl(pmd->ka_fd, TUNSETCARRIER, &carrier);
+	if (ret < 0) {
+		TAP_LOG(ERR, "%s: ioctl(TUNSETCARRIER) failed: %s",
+			pmd->name, strerror(errno));
+		return ret;
+	}
+#else
+	(void)pmd;
+	(void)carrier;
+#endif
+	return 0;
+}
+
 static int
 tap_gso_ctx_setup(struct rte_gso_ctx *gso_ctx, struct rte_eth_dev *dev)
 {
@@ -1559,6 +1575,11 @@ tap_rx_queue_setup(struct rte_eth_dev *dev,
 		tmp = &(*tmp)->next;
 	}
 
+	/* set carrier after creating at least one rxq */
+	ret = tap_carrier_set(internals, 1);
+	if (ret < 0)
+		goto error;
+
 	TAP_LOG(DEBUG, "  RX TUNTAP device name %s, qid %d on fd %d",
 		internals->name, rx_queue_id,
 		process_private->fds[rx_queue_id]);
@@ -1691,6 +1712,9 @@ tap_netns_change(struct rte_eth_dev *dev)
 		TAP_LOG(WARNING, "%s: failed to recreate LSC interrupt socket",
 			pmd->name);
 
+	/* Force carrier back after switching netns */
+	tap_carrier_set(pmd, 1);
+
 	/* Switch back to original namespace */
 	if (setns(orig_netns_fd, CLONE_NEWNET) < 0)
 		TAP_LOG(ERR, "%s: failed to return to original netns: %s",
-- 
2.51.1