selftests/bpf: add checks on extack messages for eBPF hw offload tests

Add checks to test that netlink extack messages are correctly displayed
in some expected error cases for eBPF offload to netdevsim with TC and
XDP.

iproute2 may be built without libmnl support, in which case the extack
messages will not be reported.  Try to detect this condition, and when
enountered print a mild warning to the user and skip the extack validation.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/bpf/test_offload.py

@@ -26,6 +26,7 @@ import time
 
 logfile = None
 log_level = 1
+skip_extack = False
 bpf_test_dir = os.path.dirname(os.path.realpath(__file__))
 pp = pprint.PrettyPrinter()
 devs = [] # devices we created for clean up
@@ -132,7 +133,7 @@ def rm(f):
     if f in files:
         files.remove(f)
 
-def tool(name, args, flags, JSON=True, ns="", fail=True):
+def tool(name, args, flags, JSON=True, ns="", fail=True, include_stderr=False):
     params = ""
     if JSON:
         params += "%s " % (flags["json"])
@@ -140,9 +141,20 @@ def tool(name, args, flags, JSON=True, ns="", fail=True):
     if ns != "":
         ns = "ip netns exec %s " % (ns)
 
-    ret, out = cmd(ns + name + " " + params + args, fail=fail)
-    if JSON and len(out.strip()) != 0:
-        return ret, json.loads(out)
+    if include_stderr:
+        ret, stdout, stderr = cmd(ns + name + " " + params + args,
+                                  fail=fail, include_stderr=True)
+    else:
+        ret, stdout = cmd(ns + name + " " + params + args,
+                          fail=fail, include_stderr=False)
+
+    if JSON and len(stdout.strip()) != 0:
+        out = json.loads(stdout)
+    else:
+        out = stdout
+
+    if include_stderr:
+        return ret, out, stderr
     else:
         return ret, out
 
@@ -181,13 +193,15 @@ def bpftool_map_list_wait(expected=0, n_retry=20):
         time.sleep(0.05)
     raise Exception("Time out waiting for map counts to stabilize want %d, have %d" % (expected, nmaps))
 
-def ip(args, force=False, JSON=True, ns="", fail=True):
+def ip(args, force=False, JSON=True, ns="", fail=True, include_stderr=False):
     if force:
         args = "-force " + args
-    return tool("ip", args, {"json":"-j"}, JSON=JSON, ns=ns, fail=fail)
+    return tool("ip", args, {"json":"-j"}, JSON=JSON, ns=ns,
+                fail=fail, include_stderr=include_stderr)
 
-def tc(args, JSON=True, ns="", fail=True):
-    return tool("tc", args, {"json":"-p"}, JSON=JSON, ns=ns, fail=fail)
+def tc(args, JSON=True, ns="", fail=True, include_stderr=False):
+    return tool("tc", args, {"json":"-p"}, JSON=JSON, ns=ns,
+                fail=fail, include_stderr=include_stderr)
 
 def ethtool(dev, opt, args, fail=True):
     return cmd("ethtool %s %s %s" % (opt, dev["ifname"], args), fail=fail)
@@ -348,13 +362,17 @@ class NetdevSim:
         return ip("link set dev %s mtu %d" % (self.dev["ifname"], mtu),
                   fail=fail)
 
-    def set_xdp(self, bpf, mode, force=False, JSON=True, fail=True):
+    def set_xdp(self, bpf, mode, force=False, JSON=True,
+                fail=True, include_stderr=False):
         return ip("link set dev %s xdp%s %s" % (self.dev["ifname"], mode, bpf),
-                  force=force, JSON=JSON, fail=fail)
+                  force=force, JSON=JSON,
+                  fail=fail, include_stderr=include_stderr)
 
-    def unset_xdp(self, mode, force=False, JSON=True, fail=True):
+    def unset_xdp(self, mode, force=False, JSON=True,
+                  fail=True, include_stderr=False):
         return ip("link set dev %s xdp%s off" % (self.dev["ifname"], mode),
-                  force=force, JSON=JSON, fail=fail)
+                  force=force, JSON=JSON,
+                  fail=fail, include_stderr=include_stderr)
 
     def ip_link_show(self, xdp):
         _, link = ip("link show dev %s" % (self['ifname']))
@@ -410,7 +428,7 @@ class NetdevSim:
         return filters
 
     def cls_bpf_add_filter(self, bpf, da=False, skip_sw=False, skip_hw=False,
-                           fail=True):
+                           fail=True, include_stderr=False):
         params = ""
         if da:
             params += " da"
@@ -419,7 +437,8 @@ class NetdevSim:
         if skip_hw:
             params += " skip_hw"
         return tc("filter add dev %s ingress bpf %s %s" %
-                  (self['ifname'], bpf, params), fail=fail)
+                  (self['ifname'], bpf, params),
+                  fail=fail, include_stderr=include_stderr)
 
     def set_ethtool_tc_offloads(self, enable, fail=True):
         args = "hw-tc-offload %s" % ("on" if enable else "off")
@@ -491,6 +510,16 @@ def check_dev_info(other_ns, ns, prog_file=None, map_file=None, removed=False):
         fail("dev" not in m.keys(), "Device parameters not reported")
         fail(dev != m["dev"], "Map's device different than program's")
 
+def check_extack(output, reference, args):
+    if skip_extack:
+        return
+    lines = output.split("\n")
+    comp = len(lines) >= 2 and lines[1] == reference
+    fail(not comp, "Missing or incorrect netlink extack message")
+
+def check_extack_nsim(output, reference, args):
+    check_extack(output, "Error: netdevsim: " + reference, args)
+
 # Parse command line
 parser = argparse.ArgumentParser()
 parser.add_argument("--log", help="output verbose log to given file")
@@ -527,6 +556,14 @@ for s in samples:
     skip(ret != 0, "sample %s/%s not found, please compile it" %
          (bpf_test_dir, s))
 
+# Check if iproute2 is built with libmnl (needed by extack support)
+_, _, err = cmd("tc qdisc delete dev lo handle 0",
+                fail=False, include_stderr=True)
+if err.find("Error: Failed to find qdisc with specified handle.") == -1:
+    print("Warning: no extack message in iproute2 output, libmnl missing?")
+    log("Warning: no extack message in iproute2 output, libmnl missing?", "")
+    skip_extack = True
+
 # Check if net namespaces seem to work
 ns = mknetns()
 skip(ns is None, "Could not create a net namespace")
@@ -558,8 +595,10 @@ try:
     sim.tc_flush_filters()
 
     start_test("Test TC offloads are off by default...")
-    ret, _ = sim.cls_bpf_add_filter(obj, skip_sw=True, fail=False)
+    ret, _, err = sim.cls_bpf_add_filter(obj, skip_sw=True,
+                                         fail=False, include_stderr=True)
     fail(ret == 0, "TC filter loaded without enabling TC offloads")
+    check_extack(err, "Error: TC offload is disabled on net device.", args)
     sim.wait_for_flush()
 
     sim.set_ethtool_tc_offloads(True)
@@ -587,8 +626,11 @@ try:
     sim.dfs["bpf_tc_non_bound_accept"] = "N"
 
     start_test("Test TC cBPF unbound bytecode doesn't offload...")
-    ret, _ = sim.cls_bpf_add_filter(bytecode, skip_sw=True, fail=False)
+    ret, _, err = sim.cls_bpf_add_filter(bytecode, skip_sw=True,
+                                         fail=False, include_stderr=True)
     fail(ret == 0, "TC bytecode loaded for offload")
+    check_extack_nsim(err, "netdevsim configured to reject unbound programs.",
+                      args)
     sim.wait_for_flush()
 
     start_test("Test TC offloads work...")
@@ -669,16 +711,24 @@ try:
          "Device parameters reported for non-offloaded program")
 
     start_test("Test XDP prog replace with bad flags...")
-    ret, _ = sim.set_xdp(obj, "offload", force=True, fail=False)
+    ret, _, err = sim.set_xdp(obj, "offload", force=True,
+                              fail=False, include_stderr=True)
     fail(ret == 0, "Replaced XDP program with a program in different mode")
-    ret, _ = sim.set_xdp(obj, "", force=True, fail=False)
+    check_extack_nsim(err, "program loaded with different flags.", args)
+    ret, _, err = sim.set_xdp(obj, "", force=True,
+                              fail=False, include_stderr=True)
     fail(ret == 0, "Replaced XDP program with a program in different mode")
+    check_extack_nsim(err, "program loaded with different flags.", args)
 
     start_test("Test XDP prog remove with bad flags...")
-    ret, _ = sim.unset_xdp("offload", force=True, fail=False)
+    ret, _, err = sim.unset_xdp("offload", force=True,
+                                fail=False, include_stderr=True)
     fail(ret == 0, "Removed program with a bad mode mode")
-    ret, _ = sim.unset_xdp("", force=True, fail=False)
+    check_extack_nsim(err, "program loaded with different flags.", args)
+    ret, _, err = sim.unset_xdp("", force=True,
+                                fail=False, include_stderr=True)
     fail(ret == 0, "Removed program with a bad mode mode")
+    check_extack_nsim(err, "program loaded with different flags.", args)
 
     start_test("Test MTU restrictions...")
     ret, _ = sim.set_mtu(9000, fail=False)
@@ -687,8 +737,9 @@ try:
     sim.unset_xdp("drv")
     bpftool_prog_list_wait(expected=0)
     sim.set_mtu(9000)
-    ret, _ = sim.set_xdp(obj, "drv", fail=False)
+    ret, _, err = sim.set_xdp(obj, "drv", fail=False, include_stderr=True)
     fail(ret == 0, "Driver should refuse to load program with MTU of 9000...")
+    check_extack_nsim(err, "MTU too large w/ XDP enabled.", args)
     sim.set_mtu(1500)
 
     sim.wait_for_flush()
@@ -724,25 +775,32 @@ try:
     sim2.set_xdp(obj, "offload")
     pin_file, pinned = pin_prog("/sys/fs/bpf/tmp")
 
-    ret, _ = sim.set_xdp(pinned, "offload", fail=False)
+    ret, _, err = sim.set_xdp(pinned, "offload",
+                              fail=False, include_stderr=True)
     fail(ret == 0, "Pinned program loaded for a different device accepted")
+    check_extack_nsim(err, "program bound to different dev.", args)
     sim2.remove()
-    ret, _ = sim.set_xdp(pinned, "offload", fail=False)
+    ret, _, err = sim.set_xdp(pinned, "offload",
+                              fail=False, include_stderr=True)
     fail(ret == 0, "Pinned program loaded for a removed device accepted")
+    check_extack_nsim(err, "xdpoffload of non-bound program.", args)
     rm(pin_file)
     bpftool_prog_list_wait(expected=0)
 
     start_test("Test mixing of TC and XDP...")
     sim.tc_add_ingress()
     sim.set_xdp(obj, "offload")
-    ret, _ = sim.cls_bpf_add_filter(obj, skip_sw=True, fail=False)
+    ret, _, err = sim.cls_bpf_add_filter(obj, skip_sw=True,
+                                         fail=False, include_stderr=True)
     fail(ret == 0, "Loading TC when XDP active should fail")
+    check_extack_nsim(err, "driver and netdev offload states mismatch.", args)
     sim.unset_xdp("offload")
     sim.wait_for_flush()
 
     sim.cls_bpf_add_filter(obj, skip_sw=True)
-    ret, _ = sim.set_xdp(obj, "offload", fail=False)
+    ret, _, err = sim.set_xdp(obj, "offload", fail=False, include_stderr=True)
     fail(ret == 0, "Loading XDP when TC active should fail")
+    check_extack_nsim(err, "TC program is already loaded.", args)
 
     start_test("Test binding TC from pinned...")
     pin_file, pinned = pin_prog("/sys/fs/bpf/tmp")
@@ -765,8 +823,10 @@ try:
 
     start_test("Test asking for TC offload of two filters...")
     sim.cls_bpf_add_filter(obj, da=True, skip_sw=True)
-    ret, _ = sim.cls_bpf_add_filter(obj, da=True, skip_sw=True, fail=False)
+    ret, _, err = sim.cls_bpf_add_filter(obj, da=True, skip_sw=True,
+                                         fail=False, include_stderr=True)
     fail(ret == 0, "Managed to offload two TC filters at the same time")
+    check_extack_nsim(err, "driver and netdev offload states mismatch.", args)
 
     sim.tc_flush_filters(bound=2, total=2)