[Autotest PATCH] virt: Only update macaddr cache when capture dhcp ACK packet

[Amos Kong <akong@redhat.com>]

Currently, tcpdump can capture both dhcp Offer and ACK packets,
macaddr cache will be updated in those to condition,
dhcp Offer packet doesn't mean the IP is already allocated to
dhcp client.

Signed-off-by: Amos Kong <akong@redhat.com>
---
 client/virt/virt_env_process.py |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/client/virt/virt_env_process.py b/client/virt/virt_env_process.py
index 51c7e8a..a7621bb 100644
--- a/client/virt/virt_env_process.py
+++ b/client/virt/virt_env_process.py
@@ -403,14 +403,20 @@ def _update_address_cache(address_cache, line):
             address_cache["last_seen"] = matches[0]
     if re.search("Client.Ethernet.Address", line, re.IGNORECASE):
         matches = re.findall(r"\w*:\w*:\w*:\w*:\w*:\w*", line)
-        if matches and address_cache.get("last_seen"):
-            mac_address = matches[0].lower()
+        if matches:
+            address_cache["last_mac"] = matches[0]
+    if re.search("DHCP-Message", line, re.IGNORECASE):
+        matches = re.findall(r"ACK", line)
+        if matches and address_cache.get("last_seen") and address_cache.get(
+                                                                 "last_mac"):
+            mac_address = address_cache.get("last_mac").lower()
             if time.time() - address_cache.get("time_%s" % mac_address, 0) > 5:
                 logging.debug("(address cache) Adding cache entry: %s ---> %s",
                               mac_address, address_cache.get("last_seen"))
             address_cache[mac_address] = address_cache.get("last_seen")
             address_cache["time_%s" % mac_address] = time.time()
             del address_cache["last_seen"]
+            del address_cache["last_mac"]
 
 
 def _take_screendumps(test, params, env):