19852 FIX bgp_peer: tolerate unexpected address byte-list lengths

SNMP devices may return BGP peer address byte-lists whose length is neither
4 (IPv4) nor 16 (IPv6). The bgp_peer parser unconditionally tried to
format such short byte strings as IPv6, which crashed with
AddressValueError: At least 3 parts expected in '7c30' and aborted section
parsing.

_convert_address now renders unexpected byte-list lengths as unknown(...)
so parsing continues for the remaining peers.

Crash-Group-ID: 3608
Jira: CMK-33980
Change-Id: I12cbeb43eba0c9fa1bf1c186f64566d7b563c31d

Author: otAAAh

.werks/19852.md

@@ -0,0 +1,21 @@
+[//]: # (werk v3)
+# bgp_peer: tolerate unexpected address byte-list lengths
+
+key        | value
+---------- | ---
+date       | 2026-04-23T08:02:53.305241+00:00
+version    | 2.6.0b1
+class      | fix
+edition    | community
+component  | checks
+level      | 1
+compatible | yes
+
+SNMP devices may return BGP peer address byte-lists whose length is neither
+4 (IPv4) nor 16 (IPv6). The `bgp_peer` parser unconditionally tried to
+format such short byte strings as IPv6, which crashed with
+`AddressValueError: At least 3 parts expected in '7c30'` and aborted
+section parsing.
+
+`_convert_address` now renders unexpected byte-list lengths as
+`unknown(...)` so parsing continues for the remaining peers.

cmk/plugins/collection/agent_based/bgp_peer.py

@@ -270,9 +270,17 @@ def _convert_address(value: str | list[int]) -> str:
     if not value:
         return "empty()"
     if isinstance(value, list):
-        return clean_v4_address(value) if len(value) == 4 else clean_v6_address(value)
+        if len(value) == 4:
+            return clean_v4_address(value)
+        if len(value) == 16:
+            return clean_v6_address(value)
+        return f"unknown({value!r})"
     split_value = value.split(".")
-    return clean_v4_address(split_value) if len(split_value) == 4 else clean_v6_address(split_value)
+    if len(split_value) == 4:
+        return clean_v4_address(split_value)
+    if len(split_value) == 16:
+        return clean_v6_address(split_value)
+    return f"unknown({value!r})"
 
 
 def _format_last_received_error(error_entry: str | list[int]) -> str:

tests/unit/cmk/plugins/collection/agent_based/test_bgp_peer.py

@@ -200,14 +200,8 @@ def test_bgp_peer_parse_cisco_2(data: StringByteTable, result: bgp_peer.Section)
     assert bgp_peer.parse_bgp_peer_cisco_2([data]) == result
 
 
-@pytest.mark.xfail(
-    strict=True,
-    reason="Crash group 3608: AddressValueError on short byte list",
-)
 def test_convert_address_short_byte_list() -> None:
-    # SNMP may return a byte-list whose length is neither 4 (IPv4) nor 16
-    # (IPv6). _convert_address must not crash on such malformed input.
-    bgp_peer._convert_address([0x7C, 0x30])
+    assert bgp_peer._convert_address([0x7C, 0x30]) == "unknown([124, 48])"
 
 
 @pytest.mark.parametrize(