fix: make no buffer space available when adding multicast memberships forgiving (#1516)

bdraco · web-flow · commit f377d5cd08d7 · 2025-02-11T19:19:10.000-06:00
diff --git a/src/zeroconf/_utils/net.py b/src/zeroconf/_utils/net.py
@@ -302,6 +302,20 @@ def add_multicast_member(
                 interface,
             )
             return False
+        if _errno == errno.ENOBUFS:
+            # https://github.com/python-zeroconf/python-zeroconf/issues/1510
+            if not is_v6 and sys.platform.startswith("linux"):
+                log.warning(
+                    "No buffer space available when adding %s to multicast group, "
+                    "try increasing `net.ipv4.igmp_max_memberships` to `1024` in sysctl.conf",
+                    interface,
+                )
+            else:
+                log.warning(
+                    "No buffer space available when adding %s to multicast group.",
+                    interface,
+                )
+            return False
         if _errno == errno.EADDRNOTAVAIL:
             log.info(
                 "Address not available when adding %s to multicast "
diff --git a/tests/utils/test_net.py b/tests/utils/test_net.py
@@ -4,6 +4,7 @@
 
 import errno
 import socket
+import sys
 import unittest
 from unittest.mock import MagicMock, Mock, patch
 
@@ -181,7 +182,7 @@ def test_set_mdns_port_socket_options_for_ip_version():
         netutils.set_mdns_port_socket_options_for_ip_version(sock, ("",), r.IPVersion.V4Only)
 
 
-def test_add_multicast_member():
+def test_add_multicast_member(caplog: pytest.LogCaptureFixture) -> None:
     sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
     interface = "127.0.0.1"
 
@@ -221,6 +222,26 @@ def test_add_multicast_member():
     with patch("socket.socket.setsockopt"):
         assert netutils.add_multicast_member(sock, interface) is True
 
+    # Ran out of IGMP memberships is forgiving and logs about igmp_max_memberships on linux
+    caplog.clear()
+    with (
+        patch.object(sys, "platform", "linux"),
+        patch("socket.socket.setsockopt", side_effect=OSError(errno.ENOBUFS, "No buffer space available")),
+    ):
+        assert netutils.add_multicast_member(sock, interface) is False
+        assert "No buffer space available" in caplog.text
+        assert "net.ipv4.igmp_max_memberships" in caplog.text
+
+    # Ran out of IGMP memberships is forgiving and logs
+    caplog.clear()
+    with (
+        patch.object(sys, "platform", "darwin"),
+        patch("socket.socket.setsockopt", side_effect=OSError(errno.ENOBUFS, "No buffer space available")),
+    ):
+        assert netutils.add_multicast_member(sock, interface) is False
+        assert "No buffer space available" in caplog.text
+        assert "net.ipv4.igmp_max_memberships" not in caplog.text
+
 
 def test_bind_raises_skips_address():
     """Test bind failing in new_socket returns None on EADDRNOTAVAIL."""
