Hi Daniel, -K is equivalent to the OpenSSH ClientAliveInterval. The server will send traffic to check that the connection is open.
-I will disconnect if there is no traffic for a certain time interval. It won't try to send any traffic over the connection, it just passively looks at what traffic is being sent. Note that it seems that currently -K messages will cause the -I idle timer to reset which isn't right, there's a pull request https://github.com/mkj/dropbear/pull/90 which I will merge soon. Cheers, Matt > On Wed 18/3/2020, at 7:22 pm, Dániel Fancsali <fancs...@gmail.com> wrote: > > Hello, > > First of all, let me just say this: awesome piece of software. Cheers! > > I am, however, a bit confused about the idle/keepalive settings. I have been > working with OpenSSH quite a bit, and do understand the concepts around > ServerAlive and ClientAlive as well as the TCPKeepAlive settings. But I still > struggle to wrap my head around -K and -I in dropbear. It's a tad bit unclear > which one maps to which one; or in other words, which one happends on what > layer. > > Maybe, my mistake here is trying to understand those in the context of the > OpenSSH settings, but on some level, it's the same protocol. > > So, looking at the code, I think this is what happens: > - Setting -Kx will send an ssh packed every x seconds, and if there's no > answer 3 times in a row, it considers the connection to be dead. So this is > essentially ServerAlive/ClientAlive mechanism. > - Specifying -Iy would say, if there's no incoming or outgoing data for y > seconds, it considers the connection dead. So this is sort of the others side > of the TCP keepalive coin. > > Is my understanding correct? If not, can someone please shed some light on > this for me? > > Regards, > Daniel
