fix: retry POP3/IMAP, DNS 8.8.8.8 fallback, debug counter, notification backoff

Agent-Logs-Url: https://github.com/christianlouis/InboxConverge/sessions/5ad49738-4b0b-4ed7-8686-07adb0ba9e5d Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
2026-05-03 22:06:12 +00:00
parent eea50f5d74
commit 92f60c6052
10 changed files with 1045 additions and 169 deletions
@@ -0,0 +1,214 @@
+"""
+Unit tests for the DNS 8.8.8.8 fallback resolver in mail_processor.py.
+
+Covers:
+  - _build_dns_query() produces a valid DNS A-record packet
+  - _parse_dns_a_response() extracts the first A record correctly
+  - _query_google_dns_sync() sends UDP query to 8.8.8.8 and returns an IPv4
+  - _resolve_ipv4_sync() falls through to 8.8.8.8 when system DNS and cache fail
+  - _resolve_ipv4_sync() caches the 8.8.8.8 result for subsequent calls
+"""
+
+import socket
+import struct
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from app.services.mail_processor import (
+    _build_dns_query,
+    _parse_dns_a_response,
+    _query_google_dns_sync,
+    _resolve_ipv4_sync,
+    _dns_cache,
+    _dns_cache_lock,
+)
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _make_dns_response(txid: int, ip: str) -> bytes:
+    """Craft a minimal valid DNS A-record response for the given IP."""
+    flags = 0x8180  # response, recursion available
+    qdcount = 1
+    ancount = 1
+    header = struct.pack(">HHHHHH", txid, flags, qdcount, ancount, 0, 0)
+    # Question: dummy single-label name "x" + QTYPE=A + QCLASS=IN
+    qname = b"\x01x\x00"
+    question = qname + struct.pack(">HH", 1, 1)
+    # Answer: pointer to question name (0xC00C), TYPE=A, CLASS=IN, TTL, RDLEN=4, IP
+    octets = tuple(int(o) for o in ip.split("."))
+    answer = struct.pack(">HHHiH", 0xC00C, 1, 1, 300, 4) + bytes(octets)
+    return header + question + answer
+
+
+# ---------------------------------------------------------------------------
+# _build_dns_query
+# ---------------------------------------------------------------------------
+
+
+class TestBuildDnsQuery:
+    def test_contains_hostname_labels(self):
+        data = _build_dns_query("pop.example.com")
+        # "pop" label should appear: length byte 3 followed by b"pop"
+        assert b"\x03pop" in data
+
+    def test_qtype_a_and_class_in(self):
+        data = _build_dns_query("mail.example.com")
+        # Last 4 bytes of question: QTYPE=0x0001, QCLASS=0x0001
+        assert data[-4:] == b"\x00\x01\x00\x01"
+
+    def test_transaction_id_is_0xAB12(self):
+        data = _build_dns_query("x.example.com")
+        txid = struct.unpack(">H", data[:2])[0]
+        assert txid == 0xAB12
+
+
+# ---------------------------------------------------------------------------
+# _parse_dns_a_response
+# ---------------------------------------------------------------------------
+
+
+class TestParseDnsAResponse:
+    def test_extracts_ip_from_valid_response(self):
+        response = _make_dns_response(0xAB12, "1.2.3.4")
+        result = _parse_dns_a_response(response, "example.com")
+        assert result == "1.2.3.4"
+
+    def test_returns_none_for_wrong_txid(self):
+        response = _make_dns_response(0x1234, "1.2.3.4")
+        result = _parse_dns_a_response(response, "example.com")
+        assert result is None
+
+    def test_returns_none_for_short_data(self):
+        assert _parse_dns_a_response(b"\x00\x01", "example.com") is None
+
+    def test_returns_none_when_no_answers(self):
+        # Build a header with ancount=0
+        header = struct.pack(">HHHHHH", 0xAB12, 0x8180, 0, 0, 0, 0)
+        assert _parse_dns_a_response(header, "x") is None
+
+
+# ---------------------------------------------------------------------------
+# _query_google_dns_sync
+# ---------------------------------------------------------------------------
+
+
+class TestQueryGoogleDnsSync:
+    def test_returns_ip_on_success(self):
+        response = _make_dns_response(0xAB12, "5.6.7.8")
+
+        mock_sock = MagicMock()
+        mock_sock.recvfrom.return_value = (response, ("8.8.8.8", 53))
+
+        with patch("socket.socket", return_value=mock_sock):
+            result = _query_google_dns_sync("pop.example.com")
+
+        assert result == "5.6.7.8"
+        mock_sock.sendto.assert_called_once()
+
+    def test_returns_none_on_socket_error(self):
+        with patch("socket.socket", side_effect=OSError("network down")):
+            result = _query_google_dns_sync("pop.example.com")
+        assert result is None
+
+    def test_returns_none_on_timeout(self):
+        mock_sock = MagicMock()
+        mock_sock.recvfrom.side_effect = socket.timeout("timed out")
+        with patch("socket.socket", return_value=mock_sock):
+            result = _query_google_dns_sync("pop.example.com")
+        assert result is None
+
+
+# ---------------------------------------------------------------------------
+# _resolve_ipv4_sync  — 8.8.8.8 fallback path
+# ---------------------------------------------------------------------------
+
+
+class TestResolveIpv4SyncGoogleFallback:
+    def setup_method(self):
+        """Clear the DNS cache before each test to avoid state bleed."""
+        with _dns_cache_lock:
+            _dns_cache.clear()
+
+    def test_falls_through_to_google_when_system_dns_and_cache_fail(self):
+        with (
+            patch(
+                "socket.getaddrinfo",
+                side_effect=OSError("Name or service not known"),
+            ),
+            patch(
+                "app.services.mail_processor._query_google_dns_sync",
+                return_value="9.10.11.12",
+            ) as mock_google,
+            patch(
+                "app.services.mail_processor.settings.DNS_CACHE_FALLBACK_ENABLED",
+                False,
+            ),
+        ):
+            result = _resolve_ipv4_sync("pop.web.de", 995)
+
+        assert result == "9.10.11.12"
+        mock_google.assert_called_once_with("pop.web.de")
+
+    def test_google_result_is_cached(self):
+        with (
+            patch(
+                "socket.getaddrinfo",
+                side_effect=OSError("Name or service not known"),
+            ),
+            patch(
+                "app.services.mail_processor._query_google_dns_sync",
+                return_value="9.10.11.12",
+            ),
+            patch(
+                "app.services.mail_processor.settings.DNS_CACHE_FALLBACK_ENABLED",
+                True,
+            ),
+        ):
+            _resolve_ipv4_sync("pop.web.de", 995)
+
+        with _dns_cache_lock:
+            cached = _dns_cache.get(("pop.web.de", 995))
+        assert cached == "9.10.11.12"
+
+    def test_returns_none_when_all_strategies_fail(self):
+        with (
+            patch(
+                "socket.getaddrinfo",
+                side_effect=OSError("Name or service not known"),
+            ),
+            patch(
+                "app.services.mail_processor._query_google_dns_sync",
+                return_value=None,
+            ),
+            patch(
+                "app.services.mail_processor.settings.DNS_CACHE_FALLBACK_ENABLED",
+                False,
+            ),
+        ):
+            result = _resolve_ipv4_sync("nonexistent.invalid", 995)
+
+        assert result is None
+
+    def test_system_dns_success_skips_google(self):
+        with (
+            patch(
+                "socket.getaddrinfo",
+                return_value=[(None, None, None, None, ("1.2.3.4", 995))],
+            ),
+            patch(
+                "app.services.mail_processor._query_google_dns_sync",
+            ) as mock_google,
+            patch(
+                "app.services.mail_processor.settings.DNS_CACHE_FALLBACK_ENABLED",
+                False,
+            ),
+        ):
+            result = _resolve_ipv4_sync("pop.example.com", 995)
+
+        assert result == "1.2.3.4"
+        mock_google.assert_not_called()