Subject: Cannot connect to netlink socket??

From: Ben Greear <[email-masked]>
Date: Fri, 17 Jul 2015 14:29:19 -0700

Any idea what can cause this?  The system was working fine earlier,
so it is compiled with netlink support, etc.

Last thing someone did was to add 258 mac-vlans on top of
an ethernet port.  Removing macvlan module did not improve
things.

'ifconfig -a' works fine.

This is on a 4.0.4 (+ local hacks) kernel, nothing overly weird in dmesg, and no
new dmesg info when this fails to work:

strace ip addr show

...

socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
setsockopt(3, SOL_SOCKET, SO_SNDBUF, [32768], 4) = 0
setsockopt(3, SOL_SOCKET, SO_RCVBUF, [1048576], 4) = 0
bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, pid=16631, groups=00000000}, [12]) = 0
sendto(3, "(\0\0\0\22\0\1\3%m\251U\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 40, 0, NULL, 0) = -1 ECONNREFUSED (Connection refused)
dup(2)                                  = 4
fcntl(4, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
brk(0)                                  = 0x1679000
brk(0x169a000)                          = 0x169a000
brk(0)                                  = 0x169a000
fstat(4, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb40d3c9000
write(4, "Cannot send dump request: Connec"..., 45Cannot send dump request: Connection refused
) = 45
close(4)                                = 0
munmap(0x7fb40d3c9000, 4096)            = 0
exit_group(1)                           = ?
+++ exited with 1 +++

A reboot 'fixed' things, and we have not been able to reproduce the
problem.

Thanks,
Ben

-- 
Ben Greear <[email-masked]>
Candela Technologies Inc  http://www.candelatech.com