mpmd: Fix fake results returned by mpmd_find

- For non-MPM Ethernet devices, mpmd_find would return a fake
  malformed discovery result which would accidentally trigger
  an mpmd_impl::make resulting in unexpected errors
- Fixed mpmd_find to return an empty device_addrs_t object if
  no MPM devices are found

1 files changed, 3 insertions, 1 deletions

diff --git a/host/lib/usrp/mpmd/mpmd_impl.cpp b/host/lib/usrp/mpmd/mpmd_impl.cpp
index 02b3e66c3..8586aa3a9 100644
--- a/host/lib/usrp/mpmd/mpmd_impl.cpp
+++ b/host/lib/usrp/mpmd/mpmd_impl.cpp
@@ -645,7 +645,9 @@ device_addrs_t mpmd_find_with_addrs(const device_addrs_t& hints)
             "Device responded: " << reply_addrs[0].to_string());
         found_devices.push_back(reply_addrs[0]);
     }
-    if (found_devices.size() == 1) {
+    if (found_devices.size() == 0) {
+        return device_addrs_t();
+    } else if (found_devices.size() == 1) {
         return found_devices;
     } else {
         return device_addrs_t(1, combine_device_addrs(found_devices));