cygwin sshd "getnameinfo failed"

To resolve your cygrunsrv error while installing an sshd_debug service, you also have to change the <service_name> and not only the <service display name> in:

cygrunsrv -I <service_name> -d "<service display name>" -p <service_path>

where

• <service_name> is the windows internal service name
• <service display name> is the name displayed in services.msc list

OR you have to stop and remove the already defined service sshd first, before trying to define it again using debug parameters.

Note: The commands below have to be entered in a shell with admin privileges. When sshd is run in debug mode with -d, -dd or -ddd, the server will not fork and will only process one connection and then stop.

To define a second sshd_debug service:

To install a second service named sshd_debug:

/usr/bin/cygrunsrv -I sshd_debug -d "CYGWIN sshd_debug" -p /usr/sbin/sshd -a "-D -d -d -d" -y tcpip

Note that a particular <service_name> or <service display name> cannot be defined more than once, otherwise an error will thrown by cygrunsrv.

Before you start your new sshd_debug service, the normal sshd service has to be stopped:

/usr/bin/cygrunsrv -E sshd

Now start the sshd_debug service:

/usr/bin/cygrunsrv -S sshd_debug

To redefine with the existing sshd service_name:

Another example which will make the cygrunsrv command from your question work (using the service name: sshd):

# Stop the service
/usr/bin/cygrunsrv -E sshd

# Remove the service
/usr/bin/cygrunsrv -R sshd

# Install using the same service_name with debug options
/usr/bin/cygrunsrv -I sshd -d "CYGWIN sshd_debug" -p /usr/sbin/sshd -a "-D -d -d -d" -y tcpip

# Start the service
/usr/bin/cygrunsrv -S sshd

To install a service under a specific account

/usr/bin/cygrunsrv -I sshd_debug -d "CYGWIN sshd_debug" -p /usr/sbin/sshd -a "-D -d -d -d" -y tcpip -u "<account_name>" -w "<password>"

Error: get_socket_address: getnameinfo 2 failed

The function get_socket_address throwing the error message is defined in canohost.c:

static char *
get_socket_address(int sock, int remote, int flags)
{
    ...
    switch (addr.ss_family) {
    case AF_INET:
    case AF_INET6:
        /* Get the address in ascii. */
        if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
            sizeof(ntop), NULL, 0, flags)) != 0) {
            error("get_socket_address: getnameinfo %d failed: %s",
                flags, ssh_gai_strerror(r));
            return NULL;
        }
        return xstrdup(ntop);
    ...
    }
}

It calls a function getnameinfo with flag NI_NUMERICHOST, which should return a string with the human readable IP address of either the (remote) peer_ipaddr or the local_ipaddr. However, the function fails with an unknown EAI_SYSTEM error (A system error occurred).

So this does not help a lot, but it might indicate that the error has to do with DNS name resolution.

To troubleshoot you could check if the name resolution is working:

# netstat: check where sshd listens and if you have any errors
netstat -ano | grep ":22"
netstat -ao | grep ":22"


# reverse dns lookup
nslookup <remote_ip_address>
nslookup <local_ip_address>

# forward dns lookup (using the hostnames returned by the above commands)
nslookup <remote_hostname>
nslookup <local_hostname>


# or for example using dig

# reverse dns lookup
dig -x <remote_ip_address>
dig -x <local_ip_address>

# forward dns lookup (using the hostnames returned by the above commands)
dig <remote_hostname> +search
dig <local_hostname> +search

• The reverse dns lookup should return the fqdn
• The forward dns lookup should return the IP address