[stunnel-users] Stunnel sending ICMP packet at startup

[Scott Gifford]

"Paul Jones" <jonesy_boy10 at hotmail.com> writes:

> Hi there,
>
> I have set up Stunnel on both the server and the client.  There is a
> firewall on the server side that only allows TCP connections through.
>
> When Stunnel is started up on the client side, the firewall is
> actually receiving an ICMP packet, not a TCP.  Is this how Stunnel
> should be working? I assume it's doing a ping or something at startup.

What's the exact packet you see?  I don't believe that stunnel sends
out ICMP packets on its own, but TCP may cause them to be generated,
for example by using path MTU discovery (which can cause "Must
Fragment" messages) or by sending data too fast (causing "Source
Quench" messages on some platforms).

----Scott.