test: add a trace-cmd helper

For now it's a very simple one, but we can use it as a base to provide
more complicated ones in the future.

Signed-off-by: Pablo Barbáchano <[email protected]>

Author: pb8o

tests/framework/microvm_helpers.py

@@ -222,3 +222,26 @@ def run_in_netns(cmd):
 
         # add a route on the host for the clone address
         run(f"ip route add {ingress_ipv4} via {veth_guest_ip}")
+
+    def trace_cmd_guest(self, fns, cmd, port=4321):
+        """Run trace-cmd on the guest, but transfer the data directly to the host."""
+        docker_apt_install("trace-cmd")
+        print("host> trace-cmd listen")
+        proc = subprocess.Popen(
+            [
+                "ip",
+                "netns",
+                "exec",
+                self.vm.netns.id,
+                "trace-cmd",
+                "listen",
+                "-p",
+                str(port),
+            ]
+        )
+        print("guest> trace-cmd record")
+        host_ip = self.vm.iface["eth0"]["iface"].host_ip
+        guest_ps = self.vm.ssh.run(
+            f"trace-cmd record -N {host_ip}:{port} -p function {" ".join(fns)} {cmd}"
+        )
+        return list(Path(".").glob("trace.*.dat"))

tools/sandbox.py

@@ -68,7 +68,6 @@ def parse_byte_size(param):
 else:
     bins = get_firecracker_binaries()
 
-print("This step may take a while to compile Firecracker ...")
 cpu_template = None
 if args.cpu_template_path is not None:
     cpu_template = json.loads(args.cpu_template_path.read_text())
@@ -96,3 +95,6 @@ def parse_byte_size(param):
 uvm2.add_net_iface()
 uvm2.basic_config(vcpu_count=args.vcpus, mem_size_mib=args.guest_mem_size // 2**20)
 uvm2.start()
+# trace-cmd needs this (DNS resolution?)
+uvm2.help.enable_ip_forwarding()
+files = uvm2.help.trace_cmd_guest(["-l", "read_msr"], cmd="sleep 5")