netdev - Re: help on iproute2 hangs

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Date:   Thu, 1 Mar 2018 10:51:49 -0800
From:   William Tu <u9012063@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        chrism@...lanox.com
Subject: Re: help on iproute2 hangs

On Thu, Mar 1, 2018 at 10:36 AM, David Ahern <dsahern@...il.com> wrote:
> On 3/1/18 10:29 AM, William Tu wrote:
>> Hi,
>>
>> We're running commands below on kernel 4.15.0:
>> 1) ip netns add at_ns0
>> 2) ip link add p0 type veth peer name ovs-p0
>> 3) ip link set p0 netns at_ns0
>> 4) ip link set dev ovs-p0 up
>
> # uname -a
> Linux kenny-jessie3 4.16.0-rc2+ #162 SMP Thu Mar 1 08:48:58 PST 2018
> x86_64 GNU/Linux
>
> # bash -x /tmp/2
> + ip netns add at_ns0
> + ip link add p0 type veth peer name ovs-p0
> + ip link set p0 netns at_ns0
> + ip link set dev ovs-p0 up
>
> Works fine for me on top of tree.
>
> What is the output of 'cat /proc/<pid>/stack' when it hangs?
>
root@osb:~/iproute2# ps aux | grep ip
root       3652  0.0  0.0  11532   884 pts/24   S+   10:43   0:00 ip
link add p0 type veth peer name ovs-p0

root@osb:~/iproute2# cat /proc/3652/stack
[<0>] __skb_wait_for_more_packets+0x103/0x160
[<0>] __skb_recv_datagram+0x69/0xc0
[<0>] skb_recv_datagram+0x3f/0x60
[<0>] netlink_recvmsg+0x59/0x420
[<0>] ___sys_recvmsg+0xee/0x230
[<0>] __sys_recvmsg+0x4e/0x90
[<0>] entry_SYSCALL_64_fastpath+0x24/0x87
[<0>] 0xffffffffffffffff

if I run strace on "ip link add p0 type veth peer name ovs-p0"
open("/usr/lib/ip/link_veth.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
such file or directory)
sendmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
groups=00000000},
msg_iov(1)=[{"X\0\0\0\20\0\5\6\315J\230Z\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
88}], msg_controllen=0, msg_flags=0}, 0) = 88
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
groups=00000000}, msg_iov(1)=[{NULL, 0}], msg_controllen=0,
msg_flags=MSG_TRUNC}, MSG_PEEK|MSG_TRUNC) = 36
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
groups=00000000},
msg_iov(1)=[{"$\0\0\0\2\0\0\1\315J\230Z1\24\0\0\0\0\0\0X\0\0\0\20\0\5\6\315J\230Z"...,
36}], msg_controllen=0, msg_flags=0}, 0) = 36

Thanks a lot
William