[PATCH dpdk] net/tap: close old LSC socket on netns change

[Robin Jarry]

When an interface is moved to another namespace, the LSC netlink socket
is recreated in the new namespace and the interrupt handle FD is updated
in place. The old socket is never closed, leaking one FD per move.

Create the new socket first, then close the previous one before updating
the handle, so that the handle never references a closed FD if socket
creation fails.

Fixes: aae3a38e9e03 ("net/tap: detect namespace change")
Cc: stable at dpdk.org

Signed-off-by: Robin Jarry <rjarry at redhat.com>
---
 drivers/net/tap/rte_eth_tap.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 1d2b71675a8c..885f1b341388 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -1938,15 +1938,21 @@ tap_lsc_intr_handle_set(struct rte_eth_dev *dev, int set)
 		return 0;
 	}
 	if (set) {
+		int fd;
+
 		/*
 		 * Subscribe to RTMGRP_LINK to receive RTM_NEWLINK (link state
 		 * changes) events. Also receives RTM_DELLINK events which are
 		 * used for namespace change detection when TUNGETDEVNETNS is
 		 * available.
 		 */
-		rte_intr_fd_set(pmd->intr_handle, tap_nl_init(RTMGRP_LINK));
-		if (unlikely(rte_intr_fd_get(pmd->intr_handle) == -1))
+		fd = tap_nl_init(RTMGRP_LINK);
+		if (unlikely(fd == -1))
 			return -EBADF;
+		/* Close the socket of the previous namespace, if any. */
+		if (rte_intr_fd_get(pmd->intr_handle) >= 0)
+			tap_nl_final(rte_intr_fd_get(pmd->intr_handle));
+		rte_intr_fd_set(pmd->intr_handle, fd);
 		return rte_intr_callback_register(
 			pmd->intr_handle, tap_dev_intr_handler, dev);
 	}
-- 
2.56.0