Dear openssh developers and users, I'm new to the list, and my apologies if this question has been asked before. I've tried to look for answers and haven't succeeded, which is why I'm asking. Here's the situation: I'm connect to a dual-stacked host with A and AAAA records. The IPv6 connectivity to the host is broken. When connecting to the host directly from my client system, the TCP connect to the IPv6 address times out after 75s, which is the TCP default timeout. After that, SSH proceeds to connect to the IPv4 address successfully. This causes a rather large delay. I can control this by setting "ConnectTimeout" to something lower, like 30s. So far, so good. However, when I'm not on a trusted network, I have to use a proxy to connect to that same dual-stacked host. I can do the proxy in one of the following ways: 1. ssh -tt proxyhost ssh -tt host 2. ProxyCommand ssh proxyhost 'exec nc %h %p 2>/dev/null' 3. ProxyCommand ssh -W [%h]:%p proxyhost 4. ProxyJump proxyhost 5a. ssh -D localhost:1080 -N proxyhost 5b. ProxyCommand nc -x localhost %h %p I don't like method #1 at all, for obvious reasons. Method #2 works well, and in fact, has the side effect of making the connection faster, since "nc" times out the TCP connection to the IPv6 address in just 10s, and falls back to the IPv4 address. But the disadvantage is that "nc" is required on the proxy, and I can't always ensure that. Methods #3 and #4 are essentially the same, and have the main advantage of not requiring any extra utilities on the proxy server. But they have one disadvantage that I've not been able to solve. They don't offer me any way to control the TCP timeout, and so I get the OS default, which is too long. This long delay in connecting to the target messes up other things that run atop ssh, such as ansible. Method #5 requests SOCKS proxy via the sshd on the proxyhost, but like with methods #3 and #4, I am beleagured by the TCP connect timeout of the proxyhost. So my question is: is there any way I can influence the timeout that sshd on the proxy uses for making the TCP connection to the target when using methods #3, #4 or #5? Regards, Anand Buddhdev _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
