[Bridge] Fw: [Bug 204389] New: bridge: AF_BRIDGE NEWNEIGH netlink message with ifidx is zero

[Stephen Hemminger]

Begin forwarded message:

Date: Wed, 31 Jul 2019 09:32:20 +0000
From: bugzilla-daemon at bugzilla.kernel.org
To: stephen at networkplumber.org
Subject: [Bug 204389] New: bridge: AF_BRIDGE NEWNEIGH netlink message with ifidx is zero


https://bugzilla.kernel.org/show_bug.cgi?id=204389

            Bug ID: 204389
           Summary: bridge: AF_BRIDGE NEWNEIGH netlink message with ifidx
                    is zero
           Product: Networking
           Version: 2.5
    Kernel Version: 4.19
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
          Assignee: stephen at networkplumber.org
          Reporter: michael-dev at fami-braun.de
        Regression: No

My application is receiving the following netlink messages from kernel:

-------------------------- BEGIN NETLINK
MESSAGE ---------------------------
 [NETLINK HEADER] 16 octets
 .nlmsg_len = 76
 .type = 28 <route/neigh::new>
 .flags = 0 <>
 .seq = 0
 .port = 0
 [PAYLOAD] 12 octets
 07 00 00 00 00 00 00 00 00 80 00 00 ............
 [ATTR 02] 6 octets
 4e db c4 30 92 f4 N..0..
 [PADDING] 2 octets
 00 00 ..
 .flags = 0 <>
 .seq = 0
 .port = 0
 [PAYLOAD] 12 octets
 07 00 00 00 00 00 00 00 00 80 00 00 ............
 [ATTR 02] 6 octets
 4e db c4 30 92 f4 N..0..
 [PADDING] 2 octets
 00 00 ..
 [ATTR 09] 4 octets
 00 00 00 00 ....
 [ATTR 03] 16 octets
 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
 [ATTR 05] 2 octets
 00 01 ..
 [PADDING] 2 octets
 00 00 ..
--------------------------- END NETLINK MESSAGE ---------------------------

Clearly, ifidex is zero here, so the application cannot correlate this NEWNEIGH
message to  any interface.

Adding a WARN_ON (ifidx=0) to fdb_fill_info gives the following backtrace:

[ 43.071801] [efb47c10] [c0510580] fdb_fill_info+0x180/0x22c (unreliable)
[ 43.071829] [efb47c50] [c0510684] fdb_notify.isra.22+0x58/0xd8
[ 43.071849] [efb47c70] [c0511b44] fdb_insert+0xa4/0x108
[ 43.071870] [efb47c90] [c051254c] br_fdb_insert+0x40/0x64
[ 43.071891] [efb47cb0] [c052b640] __vlan_add+0xe50/0xf24
[ 43.071911] [efb47d20] [c052a77c] br_vlan_add+0x528/0x59c
[ 43.071931] [efb47d70] [c052c38c] br_vlan_init+0x90/0xd4
[ 43.071951] [efb47da0] [c050f96c] br_dev_init+0xc8/0x170
[ 43.071983] [efb47de0] [c03cff8c] register_netdevice+0x148/0x6e8
[ 43.072003] [efb47e20] [c03d0554] register_netdev+0x28/0x50
[ 43.072026] [efb47e30] [c05154f4] br_add_bridge+0x44/0x78
[ 43.072047] [efb47e40] [c0517ce8] br_ioctl_deviceless_stub+0x2c4/0x2f0
[ 43.072069] [efb47e80] [c03a372c] sock_ioctl+0x17c/0x3d8
[ 43.072091] [efb47ed0] [c017655c] do_vfs_ioctl+0x7ac/0x894
[ 43.072111] [efb47f20] [c0176684] ksys_ioctl+0x40/0x74
[ 43.072140] [efb47f40] [c0011288] ret_from_syscall+0x0/0x3c

So clearly br_vlan_init triggers a NEWNEIGH message before bridge creation has
been completed and an ifindex assigned.

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