net/tap: fix getting max iovec

If the value _SC_IOV_MAX is missing, sysconf returns -1.
In this case, iov_max is set to a default value of 1024.
This should never happen except for redhat bug:
   https://bugzilla.redhat.com/show_bug.cgi?id=1504165

Fixes: ec12df9504fe ("net/tap: fix support for large Rx queues")
Cc: stable@dpdk.org
Signed-off-by: Oleg Polyakov <olegp123@walla.co.il>
Acked-by: Keith Wiles <keith.wiles@intel.com>

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 6f5109f..9aae4c7 100644 (file)
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -68,6 +68,8 @@
 /* IPC key for queue fds sync */
 #define TAP_MP_KEY "tap_mp_sync_queues"
 
+#define TAP_IOV_DEFAULT_MAX 1024
+
 static int tap_devices_count;
 static struct rte_vdev_driver pmd_tap_drv;
 static struct rte_vdev_driver pmd_tun_drv;
@@ -1326,6 +1328,13 @@ tap_rx_queue_setup(struct rte_eth_dev *dev,
        struct rx_queue *rxq = &internals->rxq[rx_queue_id];
        struct rte_mbuf **tmp = &rxq->pool;
        long iov_max = sysconf(_SC_IOV_MAX);
+
+       if (iov_max <= 0) {
+               TAP_LOG(WARNING,
+                       "_SC_IOV_MAX is not defined. Using %d as default",
+                       TAP_IOV_DEFAULT_MAX);
+               iov_max = TAP_IOV_DEFAULT_MAX;
+       }
        uint16_t nb_desc = RTE_MIN(nb_rx_desc, iov_max - 1);
        struct iovec (*iovecs)[nb_desc + 1];
        int data_off = RTE_PKTMBUF_HEADROOM;