Retry DNS queries if they time out (#193)

* Start work on DNS timeout retries

* Add timeout retries to SPF

* Add timeout_retries to mta_sts

* Add --timeout-retries to the CLI

* Add --timeout -retries to the CLI

---------

Co-authored-by: Sean Whalen <seanthegeek@users.noreply.github.com>

Author: seanthegeek

checkdmarc/__init__.py

@@ -59,6 +59,7 @@ def check_domains(
     nameservers: list[str] = None,
     resolver: dns.resolver.Resolver = None,
     timeout: float = 2.0,
+    timeout_retries: int = 2,
     wait: float = 0.0,
 ) -> Union[OrderedDict, list[OrderedDict]]:
     """
@@ -79,6 +80,7 @@ def check_domains(
         resolver (dns.resolver.Resolver): A resolver object to use for DNS
                                           requests
         timeout (float): number of seconds to wait for an answer from DNS
+        timeout_retries (int): The number of times to reattempt a query after a timeout
         wait (float): number of seconds to wait between processing domains
 
     Returns:
@@ -139,11 +141,16 @@ def check_domains(
             nameservers=nameservers,
             resolver=resolver,
             timeout=timeout,
+            timeout_retries=timeout_retries,
         )
 
         mta_sts_mx_patterns = None
         domain_results["mta_sts"] = check_mta_sts(
-            domain, nameservers=nameservers, resolver=resolver, timeout=timeout
+            domain,
+            nameservers=nameservers,
+            resolver=resolver,
+            timeout=timeout,
+            timeout_retries=timeout_retries,
         )
         if domain_results["mta_sts"]["valid"]:
             mta_sts_mx_patterns = domain_results["mta_sts"]["policy"]["mx"]
@@ -155,6 +162,7 @@ def check_domains(
             nameservers=nameservers,
             resolver=resolver,
             timeout=timeout,
+            timeout_retries=timeout_retries,
         )
 
         domain_results["spf"] = check_spf(
@@ -163,6 +171,7 @@ def check_domains(
             nameservers=nameservers,
             resolver=resolver,
             timeout=timeout,
+            timeout_retries=timeout_retries,
         )
 
         domain_results["dmarc"] = check_dmarc(
@@ -172,10 +181,15 @@ def check_domains(
             nameservers=nameservers,
             resolver=resolver,
             timeout=timeout,
+            timeout_retries=timeout_retries,
         )
 
         domain_results["smtp_tls_reporting"] = check_smtp_tls_reporting(
-            domain, nameservers=nameservers, resolver=resolver, timeout=timeout
+            domain,
+            nameservers=nameservers,
+            resolver=resolver,
+            timeout=timeout,
+            timeout_retries=timeout_retries,
         )
         if bimi_selector is not None:
             domain_results["bimi"] = check_bimi(
@@ -186,6 +200,7 @@ def check_domains(
                 nameservers=nameservers,
                 resolver=resolver,
                 timeout=timeout,
+                timeout_retries=timeout_retries,
             )
 
         results.append(domain_results)
@@ -205,6 +220,7 @@ def check_ns(
     nameservers: list[str] = None,
     resolver: dns.resolver.Resolver = None,
     timeout: float = 2.0,
+    timeout_retries: int = 2,
 ) -> OrderedDict:
     """
     Returns a dictionary of nameservers and warnings or a dictionary with an
@@ -236,6 +252,7 @@ def check_ns(
             nameservers=nameservers,
             resolver=resolver,
             timeout=timeout,
+            timeout_retries=timeout_retries,
         )
     except DNSException as error:
         ns_results = OrderedDict([("hostnames", []), ("error", error.__str__())])

checkdmarc/_cli.py

@@ -80,6 +80,13 @@ def _main():
         type=float,
         default=2.0,
     )
+    arg_parser.add_argument(
+        "--timeout-retries",
+        help="number of times to reattempt a query after a timeout (default 2)",
+        type=int,
+        default=2,
+    )
+
     arg_parser.add_argument(
         "-b", "--bimi-selector", default="default", help="the BIMI selector to use"
     )
@@ -137,6 +144,7 @@ def _main():
         include_tag_descriptions=args.descriptions,
         nameservers=args.nameserver,
         timeout=args.timeout,
+        timeout_retries=args.timeout_retries,
         bimi_selector=args.bimi_selector,
         wait=args.wait,
     )

checkdmarc/bimi.py

@@ -650,6 +650,7 @@ def _query_bimi_record(
     nameservers: list[str] = None,
     resolver: dns.resolver.Resolver = None,
     timeout: float = 2.0,
+    timeout_retries: int = 2,
 ):
     """
     Queries DNS for a BIMI record
@@ -661,6 +662,7 @@ def _query_bimi_record(
         resolver (dns.resolver.Resolver): A resolver object to use for DNS
                                           requests
         timeout (float): number of seconds to wait for a record from DNS
+        timeout_retries (int): The number of times to reattempt a query after a timeout
 
     Returns:
         str: A record string or None
@@ -674,7 +676,12 @@ def _query_bimi_record(
 
     try:
         records = query_dns(
-            target, "TXT", nameservers=nameservers, resolver=resolver, timeout=timeout
+            target,
+            "TXT",
+            nameservers=nameservers,
+            resolver=resolver,
+            timeout=timeout,
+            timeout_retries=timeout_retries,
         )
         for record in records:
             if record.startswith(txt_prefix):
@@ -730,6 +737,7 @@ def query_bimi_record(
     nameservers: list[str] = None,
     resolver: dns.resolver.Resolver = None,
     timeout: float = 2.0,
+    timeout_retries: int = 2,
 ) -> OrderedDict:
     """
     Queries DNS for a BIMI record
@@ -741,6 +749,7 @@ def query_bimi_record(
         resolver (dns.resolver.Resolver): A resolver object to use for DNS
                                           requests
         timeout (float): number of seconds to wait for a record from DNS
+        timeout_retries (int): The number of times to reattempt a query after a timeout
 
     Returns:
         OrderedDict: An ``OrderedDict`` with the following keys:
@@ -765,10 +774,16 @@ def query_bimi_record(
         nameservers=nameservers,
         resolver=resolver,
         timeout=timeout,
+        timeout_retries=timeout_retries,
     )
     try:
         root_records = query_dns(
-            domain, "TXT", nameservers=nameservers, resolver=resolver, timeout=timeout
+            domain,
+            "TXT",
+            nameservers=nameservers,
+            resolver=resolver,
+            timeout=timeout,
+            timeout_retries=timeout_retries,
         )
         for root_record in root_records:
             if root_record.startswith("v=BIMI1"):
@@ -780,7 +795,11 @@ def query_bimi_record(
 
     if record is None and domain != base_domain:
         record = _query_bimi_record(
-            base_domain, nameservers=nameservers, resolver=resolver, timeout=timeout
+            base_domain,
+            nameservers=nameservers,
+            resolver=resolver,
+            timeout=timeout,
+            timeout_retries=timeout_retries,
         )
         location = base_domain
     if record is None:
@@ -993,6 +1012,7 @@ def check_bimi(
     nameservers: list[str] = None,
     resolver: dns.resolver.Resolver = None,
     timeout: float = 2.0,
+    timeout_retries: int = 2,
 ) -> OrderedDict:
     """
     Returns a dictionary with a parsed BIMI record or an error.
@@ -1012,6 +1032,7 @@ def check_bimi(
         resolver (dns.resolver.Resolver): A resolver object to use for DNS
                                           requests
         timeout (float): number of seconds to wait for an answer from DNS
+        timeout_retries (int): The number of times to reattempt a query after a timeout
 
     Returns:
         OrderedDict: An ``OrderedDict`` with the following keys: