Update allreduce_bench.py (#318)

Replacing hardcoded network interface name for generic discovery
strategy.

---------

Co-authored-by: Changho Hwang <changhohwang@microsoft.com>

python/mscclpp_benchmark/allreduce_bench.py

@@ -17,6 +17,7 @@ import mscclpp.comm as mscclpp_comm
 from mscclpp import ProxyService, is_nvls_supported
 from prettytable import PrettyTable
 import netifaces as ni
+import ipaddress
 
 data_type = cp.float32
 
@@ -222,6 +223,31 @@ def run_benchmark(
     return memory.nbytes, mscclpp_algBw, nccl_algBw, speed_up
 
 
+def is_valid(ip):
+    """
+    Check if the IP address is valid for connecting to other devices.
+    This excludes loopback (127.0.0.1) and link-local (169.254.x.x) addresses.
+    """
+    ip_obj = ipaddress.ip_address(ip)
+    return not (ip_obj.is_loopback or ip_obj.is_link_local or ip_obj.is_multicast)
+
+
+def get_netinterface_info():
+    """
+    Returns the name of the first network interface with a valid IP address that it finds.
+    """
+    interfaces = ni.interfaces()
+    for interface in interfaces:
+        addresses = ni.ifaddresses(interface)
+        if ni.AF_INET in addresses:
+            for addr in addresses[ni.AF_INET]:
+                ip_address = addr["addr"]
+                if is_valid(ip_address):
+                    print(f"Selected Interface: {interface}, IP Address: {ip_address}")
+                    return interface, ip_address
+    return None, None
+
+
 if __name__ == "__main__":
     shm_comm = MPI.COMM_WORLD.Split_type(MPI.COMM_TYPE_SHARED, 0, MPI.INFO_NULL)
     N_GPUS_PER_NODE = shm_comm.size
@@ -229,8 +255,7 @@ if __name__ == "__main__":
     cp.cuda.Device(MPI.COMM_WORLD.rank % N_GPUS_PER_NODE).use()
 
     # create a MscclppGroup
-    network_interface = "eth0"
-    my_ip = ni.ifaddresses(network_interface)[ni.AF_INET][0]["addr"]
+    network_interface, my_ip = get_netinterface_info()
     root_ip = MPI.COMM_WORLD.bcast(my_ip, root=0)
     ifIpPortTrio = network_interface + ":" + root_ip + ":50000"  # some random port
     mscclpp_group = mscclpp_comm.CommGroup(