From dcf0b7d5ada317b7e5abd082f7bc22ce609087ae Mon Sep 17 00:00:00 2001
From: Federico Capoano <f.capoano@openwisp.io>
Date: Wed, 17 Jan 2024 18:53:03 -0300
Subject: [PATCH] [fix] Skip adding empty DHCP lease tables

---
 .../files/lib/openwisp-monitoring/dhcp.lua    |  7 ++--
 openwisp-monitoring/tests/test_dhcp.lua       | 36 ++++++++++++++-----
 .../test_files/dhcp_leases_irregular.txt      |  2 ++
 3 files changed, 35 insertions(+), 10 deletions(-)
 create mode 100644 openwisp-monitoring/tests/test_files/dhcp_leases_irregular.txt

diff --git a/openwisp-monitoring/files/lib/openwisp-monitoring/dhcp.lua b/openwisp-monitoring/files/lib/openwisp-monitoring/dhcp.lua
index 1edffd97..af4f0d71 100644
--- a/openwisp-monitoring/files/lib/openwisp-monitoring/dhcp.lua
+++ b/openwisp-monitoring/files/lib/openwisp-monitoring/dhcp.lua
@@ -11,13 +11,16 @@ function dhcp.parse_dhcp_lease_file(path, leases)
   for line in f:lines() do
     local expiry, mac, ip, name, id = line:match(
       '(%S+)%s+(%S+)%s+(%S+)%s+(%S+)%s+(%S+)')
-    table.insert(leases, {
+    local lease = {
       expiry = tonumber(expiry),
       mac = mac,
       ip = ip,
       client_name = name,
       client_id = id
-    })
+    }
+    if not utils.is_table_empty(lease) then
+      table.insert(leases, lease)
+    end
   end
 
   return leases
diff --git a/openwisp-monitoring/tests/test_dhcp.lua b/openwisp-monitoring/tests/test_dhcp.lua
index 10c76c53..700acd06 100644
--- a/openwisp-monitoring/tests/test_dhcp.lua
+++ b/openwisp-monitoring/tests/test_dhcp.lua
@@ -5,11 +5,23 @@ local cjson = require('cjson')
 local luaunit = require('luaunit')
 local dhcp_data = require('test_files/dhcp_data')
 
+local dhcp_open = function(arg)
+  local test_file_dir = './test_files/'
+  if arg == '/tmp/dhcp.leases' then
+    return io.open(test_file_dir .. 'dhcp_leases.txt')
+  elseif arg == '/tmp/dhcp.leases.irregular' then
+    return io.open(test_file_dir .. 'dhcp_leases_irregular.txt')
+  else
+    return nil
+  end
+end
+
 TestDhcp = {
   setUp = function()
     local env = require('main_env')
     package.loaded.uci = env.uci
     package.loaded.io = env.io
+    package.loaded.io.open = dhcp_open
   end,
   tearDown = function() end
 }
@@ -17,7 +29,6 @@ TestDhcp = {
 TestNetJSON = {
   setUp = function()
     local env = require('basic_env')
-    local test_file_dir = './test_files/'
     package.loaded.ubus = env.ubus
     package.loaded.io = {
       popen = function(arg)
@@ -30,13 +41,7 @@ TestNetJSON = {
         f:seek('set', 0)
         return f
       end,
-      open = function(arg)
-        if arg == '/tmp/dhcp.leases' then
-          return io.open(test_file_dir .. 'dhcp_leases.txt')
-        else
-          return nil
-        end
-      end,
+      open = dhcp_open,
       write = function(...) return nil end
     }
     package.loaded.uci = {
@@ -78,4 +83,19 @@ function TestNetJSON.test_dhcp()
   luaunit.assertEquals(netjson["dhcp_leases"][1]["expiry"], 1620788343)
 end
 
+function TestDhcp.test_dhcp_leases_irregular()
+  local dhcp_functions = require('dhcp')
+  local expected = {
+    {
+      client_id = "01:c6:df:44:00:00:00",
+      client_name = "*",
+      expiry = 1705556643,
+      ip = "192.168.1.163",
+      mac = "c6:df:44:00:00:00"
+    }
+  }
+  local parsed = dhcp_functions.parse_dhcp_lease_file('/tmp/dhcp.leases.irregular', {})
+  luaunit.assertEquals(parsed, expected)
+end
+
 os.exit(luaunit.LuaUnit.run())
diff --git a/openwisp-monitoring/tests/test_files/dhcp_leases_irregular.txt b/openwisp-monitoring/tests/test_files/dhcp_leases_irregular.txt
new file mode 100644
index 00000000..d83fc9aa
--- /dev/null
+++ b/openwisp-monitoring/tests/test_files/dhcp_leases_irregular.txt
@@ -0,0 +1,2 @@
+1705556643 c6:df:44:00:00:00 192.168.1.163 * 01:c6:df:44:00:00:00
+duid 00:01:00:01:00:00:00:00:00:a0:26:36:01:90