dpif-linux: Make dpif_linux_port_query_by_name() query only one datapath.

The kernel will report a vport with the given name in any datapath, but
userspace only wants a vport with the given name in a specific datapath.
Receiving information on a vport in an unexpected datapath yields bizarre
and hard-to-debug problems.

Bug #9889.
Signed-off-by: Ben Pfaff <blp@nicira.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c
index 1f6c2c02..818d86f8 100644
--- a/lib/dpif-linux.c
+++ b/lib/dpif-linux.c
@@ -457,9 +457,15 @@ dpif_linux_port_query__(const struct dpif *dpif, uint32_t port_no,
 
     error = dpif_linux_vport_transact(&request, &reply, &buf);
     if (!error) {
-        dpif_port->name = xstrdup(reply.name);
-        dpif_port->type = xstrdup(netdev_vport_get_netdev_type(&reply));
-        dpif_port->port_no = reply.port_no;
+        if (reply.dp_ifindex != request.dp_ifindex) {
+            /* A query by name reported that 'port_name' is in some datapath
+             * other than 'dpif', but the caller wants to know about 'dpif'. */
+            error = ENODEV;
+        } else {
+            dpif_port->name = xstrdup(reply.name);
+            dpif_port->type = xstrdup(netdev_vport_get_netdev_type(&reply));
+            dpif_port->port_no = reply.port_no;
+        }
         ofpbuf_delete(buf);
     }
     return error;