chore(dns) error handling and debug improvements

kong/resty/dns/client.lua

@@ -31,6 +31,9 @@ local log = ngx.log
 local ERR = ngx.ERR
 local WARN = ngx.WARN
 local DEBUG = ngx.DEBUG
+--[[
+  DEBUG = ngx.WARN
+--]]
 local PREFIX = "[dns-client] "
 local timer_at = ngx.timer.at
 local get_phase = ngx.get_phase
@@ -67,6 +70,8 @@ local typeOrder            -- array with order of types to try
 local clientErrors = {     -- client specific errors
   [100] = "cache only lookup failed",
   [101] = "empty record received",
+  [102] = "invalid name, bad IPv4",
+  [103] = "invalid name, bad IPv6",
 }
 
 for _,v in ipairs(orderValids) do orderValids[v:upper()] = v end
@@ -980,8 +985,8 @@ local function check_ipv6(qname, qtype, try_list)
     -- return a "server error"
     try_status(try_list, "bad IPv6")
     record = {
-      errcode = 3,
-      errstr = "name error",
+      errcode = 103,
+      errstr = clientErrors[103],
     }
   end
   cacheinsert(record, qname, qtype)
@@ -1018,8 +1023,8 @@ local function check_ipv4(qname, qtype, try_list)
     -- return a "server error"
     try_status(try_list, "bad IPv4")
     record = {
-      errcode = 3,
-      errstr = "name error",
+      errcode = 102,
+      errstr = clientErrors[102],
     }
   end
   cacheinsert(record, qname, qtype)
@@ -1162,7 +1167,7 @@ local function resolve(qname, r_opts, dnsCacheOnly, try_list)
         records = nil
         -- luacheck: pop
         err = "recursion detected"
-        try_status(try_list, "recursion detected")
+        try_status(try_list, err)
         return nil, err, try_list
       end
     end
@@ -1181,7 +1186,7 @@ local function resolve(qname, r_opts, dnsCacheOnly, try_list)
       -- check for CNAME records, and dereferencing the CNAME
       if (records[1] or EMPTY).type == _M.TYPE_CNAME and qtype ~= _M.TYPE_CNAME then
         opts.qtype = nil
-        try_status(try_list, "dereferencing")
+        try_status(try_list, "dereferencing CNAME")
         return resolve(records[1].cname, opts, dnsCacheOnly, try_list)
       end
 
@@ -1208,7 +1213,7 @@ local function resolve(qname, r_opts, dnsCacheOnly, try_list)
     if records.errcode then
       -- the query type didn't match the ip address, or a bad ip address
       return nil,
-             ("dns server error: %s %s"):format(records.errcode, records.errstr),
+             ("dns client error: %s %s"):format(records.errcode, records.errstr),
              try_list
     end
     -- valid ipv4 or ipv6
@@ -1289,7 +1294,7 @@ local function resolve(qname, r_opts, dnsCacheOnly, try_list)
         if records[1].type == _M.TYPE_CNAME and qtype ~= _M.TYPE_CNAME then
           -- dereference CNAME
           opts.qtype = nil
-          try_status(try_list, "dereferencing")
+          try_status(try_list, "dereferencing CNAME")
           return resolve(records[1].cname, opts, dnsCacheOnly, try_list)
         end
 

spec/01-unit/21-dns-client/02-client_spec.lua

@@ -7,6 +7,8 @@ local pretty = require("pl.pretty").write
 -- define a constant for that error message
 local NOT_FOUND_ERROR = "dns server error: 3 name error"
 local EMPTY_ERROR = "dns client error: 101 empty record received"
+local BAD_IPV4_ERROR = "dns client error: 102 invalid name, bad IPv4"
+local BAD_IPV6_ERROR = "dns client error: 103 invalid name, bad IPv6"
 
 local gettime, sleep
 if ngx then
@@ -845,7 +847,7 @@ describe("[DNS client]", function()
       false
     )
     assert.equal(0, callcount)
-    assert.equal(NOT_FOUND_ERROR, err)
+    assert.equal(BAD_IPV4_ERROR, err)
   end)
 
   it("fetching IPv6 address as AAAA type", function()
@@ -893,7 +895,7 @@ describe("[DNS client]", function()
       false
     )
     assert.equal(0, callcount)
-    assert.equal(NOT_FOUND_ERROR, err)
+    assert.equal(BAD_IPV6_ERROR, err)
   end)
 
   it("fetching invalid IPv6 address", function()
@@ -908,7 +910,7 @@ describe("[DNS client]", function()
 
     local answers, err, history = client.resolve(host)
     assert.is_nil(answers)
-    assert.equal(NOT_FOUND_ERROR, err)
+    assert.equal(BAD_IPV6_ERROR, err)
     assert(tostring(history):find("bad IPv6", nil, true))
   end)