[Users] Localhost connectivity stops working

[Baptiste Ashka]

Hi,

I am encountering a network-related issue with some Debian OpenVZ 6
(2.6.32-openvz-042stab127.2-amd64) machines that occurs at seemingly random
and that only happens on OpenVZ nodes: all connect() syscalls that try to
connect to 127.0.0.1 (IPv4) will timeout. Connecting to :: (IPv6) works,
any other 127.x.x.x addresses work. Rebooting the hardware node is the most
consistent workaround we have (but it does not fix the issue every time
either), stopping a bunch of CTs sometimes also fixes the issue, sometimes
weird things happen (e.g. suspend a specific CT, 127.0.0.1 works again,
resume the CT, 127.0.0.1 stops working, suspend this CT again, 127.0.0.1
does not work). This does not appear to be a socket count limit issue, from
what I can tell.

This happens sporadically but consistently on all our machines. Is anyone
having this issue/something close to it?

strace of a connect() syscall using curl:
socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 3
setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
connect(3, {sa_family=AF_INET, sin_port=htons(8080),
sin_addr=inet_addr("127.0.0.1")}, 16) = -1 ETIMEDOUT (Connection timed out)

Thank you
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