run_cmd_inside_vmm now accepts longer cmds

tests/test_run_reference_vmm.py

@@ -7,6 +7,7 @@
 import subprocess
 import tempfile
 import platform
+import sys
 
 import time
 from subprocess import PIPE
@@ -225,7 +226,24 @@ def run_cmd_inside_vm(cmd, vmm_process, prompt, timeout=5):
 
        Note: `cmd` and `prompt` should be a `bytes` object and not `str`.
     """
-    cmd = cmd.strip() + b'\r\n'
+    cmd = cmd.strip()
+
+    # The max capacity of the buffer for serial console is 64.(https://github.com/rust-vmm/vm-superio/blob/282bae92878936086606715412494fa81151efba/crates/vm-superio/src/serial.rs#L34)
+    # So we split the command at 63 bytes. 1 extra is reserved for \r at the end.
+    # empty string is of size 33. sys.getsizeof(b'') = 33.
+    # 63-33 = 30. So we add at max 30 [0-29] chars inside the command buffer.
+    break_at = 30
+    size = sys.getsizeof(cmd)
+    while size >= 64:
+        cmd_i = cmd[:break_at]
+
+        vmm_process.stdin.write(cmd_i)
+        vmm_process.stdin.flush()
+        time.sleep(1)
+        cmd = cmd[break_at:]
+        size = sys.getsizeof(cmd)
+
+    cmd = cmd + b'\r\n'
 
     vmm_process.stdin.write(cmd)
     vmm_process.stdin.flush()
@@ -433,17 +451,17 @@ def test_reference_vmm_with_net_device(kernel , disk):
     """Start the reference VMM and verify the tap device."""
 
     prompt = "root@ubuntu-rust-vmm:~#"
-    # These are defults values for net
-    # device.
+    # These are defults values for net devices.
     tap_device = "tap0"
     guest_ip = "172.16.0.2"
     host_ip = "172.16.0.1"
     mask = 24
     guest_ip_with_mask = f"{guest_ip}/{mask}"
-    try:
-        setup_host()
 
-        vmm_process, _ = start_vmm_process(kernel, disk_path=disk ,tap_device=tap_device)
+    setup_host()
+
+    try:
+        vmm_process, temp_file_path = start_vmm_process(kernel, disk_path=disk ,tap_device=tap_device)
 
         setup_guest(vmm_process , prompt)
 
@@ -460,43 +478,35 @@ def test_reference_vmm_with_net_device(kernel , disk):
 
     finally:
         shutdown(vmm_process)
+        if temp_file_path:
+            os.remove(temp_file_path)
+
+        # we will always clear the tap device no matter if the
+        # test passes or fails.
         clean_tap()
 
 
 def setup_guest(vmm_process , prompt , guest_ip_with_mask="172.16.0.2/24" , host_ip="172.16.0.1"):
     """Configure the guest vm with the tap device"""
+
+    # To clear the inital stdout which was printed while 
+    # booting the vmm.
     expect_string(vmm_process,prompt)
-    # This is a little hack to write the command in chunks
-    # because there is a character limit. `i_` represents
-    # an incomplete command.
-    i_add_addr1_cmd = "i_ip addr add "
-    i_add_addr2_cmd = f"i_{guest_ip_with_mask} "
-    add_addr3_cmd = "dev eth0"
+
+    add_addr_cmd = f"ip addr add {guest_ip_with_mask} dev eth0"
     interface_up_cmd = "ip link set eth0 up"
-    i_add_route1_cmd = "i_ip route add default "
-    i_add_route2_cmd = f"i_via {host_ip} "
-    add_route3_cmd = "dev eth0"
+    add_route_cmd = f"ip route add default via {host_ip} dev eth0"
     show_interface_cmd = "ip a"
 
-    all_cmds = [i_add_addr1_cmd ,i_add_addr2_cmd, add_addr3_cmd , interface_up_cmd , i_add_route1_cmd, i_add_route2_cmd ,add_route3_cmd]
+    all_cmds = [add_addr_cmd , interface_up_cmd , add_route_cmd]
 
     for cmd in all_cmds:        
-        in_between = cmd[:2] == "i_"
-        if in_between:
-            cmd = cmd[2:]
-            cmd = cmd.encode()
-        else:
-            cmd = cmd.encode().strip() + b'\r\n'
-        vmm_process.stdin.write(cmd)
-        vmm_process.stdin.flush()
-        time.sleep(1)
-
-    # just to flush out any data on stdout
-    os.read(vmm_process.stdout.fileno(), 4096)
-
+        _ = run_cmd_inside_vm(cmd.encode() , vmm_process , prompt.encode())
+
     # verifying that guest interface is setup properly
     output = run_cmd_inside_vm(show_interface_cmd.encode() , vmm_process ,prompt.encode() , timeout=10 )    
     output = b''.join(output).decode()
+
     assert output.find(f"inet {guest_ip_with_mask} scope global eth0") != -1
 
 def setup_host(tap_device="tap0" , host_ip_with_mask="172.16.0.1/24"):