usertools: print process name when telemetry connects

When the dpdk-telemetry client connects to a DPDK instance, we can use the
PID provided in the initial connection message to query from /proc the name
of the process we are connected to, and display that to the user. We use
the "cmdline" procfs entry for the query since that is available on both
Linux and FreeBSD (assuming procfs is mounted on the BSD instance).

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Kevin Laatz <kevin.laatz@intel.com>

usertools/dpdk-telemetry.py

@@ -11,6 +11,7 @@
 import os
 import glob
 import json
+import errno
 import readline
 import argparse
 
@@ -33,6 +34,20 @@ def read_socket(sock, buf_len, echo=True):
     return ret
 
 
+def get_app_name(pid):
+    """ return the app name for a given PID, for printing """
+    proc_cmdline = os.path.join('/proc', str(pid), 'cmdline')
+    try:
+        with open(proc_cmdline) as f:
+            argv0 = f.read(1024).split('\0')[0]
+            return os.path.basename(argv0)
+    except IOError as e:
+        # ignore file not found errors
+        if e.errno != errno.ENOENT:
+            raise
+    return None
+
+
 def handle_socket(path):
     """ Connect to socket and handle user input """
     sock = socket.socket(socket.AF_UNIX, socket.SOCK_SEQPACKET)
@@ -46,6 +61,9 @@ def handle_socket(path):
         return
     json_reply = read_socket(sock, 1024)
     output_buf_len = json_reply["max_output_len"]
+    app_name = get_app_name(json_reply["pid"])
+    if app_name:
+        print('Connected to application: "%s"' % app_name)
 
     # get list of commands for readline completion
     sock.send("/".encode())