autoneg bug

backend/src/utilities/bridge_link_state_manager.py

@@ -553,8 +553,30 @@ class BridgeLinkStateWatcher:
             return None
 
         cmd = [_ETHTOOL_BIN, "-s", target_ifname]
+        change_summary: Optional[str] = None
         if source_profile.autoneg is True:
-            cmd.extend(["autoneg", "on"])
+            if source_profile.speed_mbps is not None and source_profile.duplex is not None:
+                # A remote peer can pull this port down to a lower negotiated speed while autoneg
+                # stays enabled locally. Mirror the effective link mode on sibling ports so they
+                # present the same downstream behavior even though the peer's exact advertisement
+                # bitmap is not visible from this host.
+                cmd.extend(
+                    [
+                        "speed",
+                        str(source_profile.speed_mbps),
+                        "duplex",
+                        source_profile.duplex,
+                        "autoneg",
+                        "off",
+                    ]
+                )
+                change_summary = (
+                    f"{target_ifname} link={source_profile.speed_mbps}Mb/"
+                    f"{source_profile.duplex}/forced-from-autoneg-peer"
+                )
+            else:
+                cmd.extend(["autoneg", "on"])
+                change_summary = f"{target_ifname} link=autoneg-on"
         elif source_profile.autoneg is False and source_profile.speed_mbps is not None and source_profile.duplex is not None:
             cmd.extend(
                 [
@@ -566,6 +588,10 @@ class BridgeLinkStateWatcher:
                     "off",
                 ]
             )
+            change_summary = (
+                f"{target_ifname} link={source_profile.speed_mbps}Mb/"
+                f"{source_profile.duplex}/autoneg-off"
+            )
         else:
             return None
 
@@ -589,11 +615,7 @@ class BridgeLinkStateWatcher:
             self.bridge_name,
             source_profile,
         )
-        return (
+        return change_summary
-            f"{target_ifname} link="
-            f"{source_profile.speed_mbps or 'unknown'}Mb/{source_profile.duplex or 'unknown'}/"
-            f"{'autoneg-on' if source_profile.autoneg else 'autoneg-off'}"
-        )
 
     def _suppress_other_members(self, states: dict[str, MemberLinkState], failing_members: list[str]) -> None:
         desired_suppressed = set(states) - set(failing_members)