selftests: drv-net: print device info at the start

When a reviewer asks a developer to run an upstream test during code
review, it's often ambiguous whether the test was actually run against
a real device, or just against netdevsim. Print the driver name and
ifname at the start of the test, e.g.:

  # Interface: enp0s13f0u1u4, driver: r8152
  TAP version 13
  1..1
  ok 1 ...

Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260803211944.2166211-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/lib/py/env.py

@@ -7,7 +7,7 @@ import time
 import json
 from pathlib import Path
 from lib.py import KsftSkipEx, KsftXfailEx
-from lib.py import ksft_setup, wait_file
+from lib.py import ksft_pr, ksft_setup, wait_file
 from lib.py import cmd, ethtool, ip, CmdExitFailure
 from lib.py import NetNS, NetdevSimDev, UserNetNS
 from .remote import Remote
@@ -31,6 +31,7 @@ class NetDrvEnvBase:
 
         # Following attrs must be set be inheriting classes
         self.dev = None
+        self.ifname = None
 
     def _load_env_file(self):
         env = os.environ.copy()
@@ -58,6 +59,22 @@ class NetDrvEnvBase:
     def __del__(self):
         pass
 
+    def _print_dev_info(self):
+        """
+        Show whether the test ran on real hardware or netdevsim.
+        Useful to confirm when results are shared on the mailing list.
+        """
+        driver = "unknown"
+        try:
+            info = ethtool(f"-i {self.ifname}").stdout
+            for line in info.splitlines():
+                if line.startswith("driver:"):
+                    driver = line.split(':', 1)[1].strip() or driver
+                    break
+        except (CmdExitFailure, FileNotFoundError):
+            pass
+        ksft_pr(f"Interface: {self.ifname}, driver: {driver}")
+
     def __enter__(self):
         ip(f"link set dev {self.dev['ifname']} up")
         wait_file(f"/sys/class/net/{self.dev['ifname']}/carrier",
@@ -94,6 +111,7 @@ class NetDrvEnv(NetDrvEnvBase):
             self.dev = self._ns.nsims[0].dev
         self.ifname = self.dev['ifname']
         self.ifindex = self.dev['ifindex']
+        self._print_dev_info()
 
     def __del__(self):
         if self._ns:
@@ -164,6 +182,7 @@ class NetDrvEpEnv(NetDrvEnvBase):
 
         self.ifname = self.dev['ifname']
         self.ifindex = self.dev['ifindex']
+        self._print_dev_info()
 
         # resolve remote interface name
         self.remote_ifname = self.resolve_remote_ifc()