[OpenSIPS-Users] CentOS7: Possible SYN flooding on port 5061

[Alexey Vasilyev]

Hi,

When switching Backup->Active with a lot of TLS clients I got this message
on CentOS 7:
kernel: TCP: request_sock_TCP: Possible SYN flooding on port 5061. Sending
cookies.

It is described for example here https://access.redhat.com/solutions/30453

And related to socket backlog limit.

It's not a problem to increase kernel limit:
sysctl -w net.core.somaxconn=2048

But the question is about OpenSIPS. What do you think, is this enough?
https://github.com/OpenSIPS/opensips/blob/ca75c705a4d74a06aec8ffe6d6e5d5c5e6fb97d6/net/tcp_conn.h#L46

/*!< TCP listen backlog count */
#define DEFAULT_TCP_LISTEN_BACKLOG 10

If we have thousands TLS/TCP connections at the same time, and for example
32 processes, so we'll have only 10*32=320 socket backlog limit for
OpenSIPS? Is this right?

Should it be increased?



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Alexey Vasilyev
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