CURLOPT_SSH_KNOWNHOSTS not accepted with libssh

[felixhaedicke]

When curl is compiled with libssh (not libssh2), calling curl_easy_setopt() with option CURLOPT_SSH_KNOWNHOSTS fails with error code CURLE_UNKNOWN_OPTION.

Although in lib/ssh-libssh.c, I found this:

  if(data->set.str[STRING_SSH_KNOWNHOSTS]) {
    infof(data, "Known hosts: %s\n", data->set.str[STRING_SSH_KNOWNHOSTS]);
    ssh_options_set(ssh->ssh_session, SSH_OPTIONS_KNOWNHOSTS,
                    data->set.str[STRING_SSH_KNOWNHOSTS]);
  }

example program

#include <assert.h>
#include <curl/curl.h>

int main()
{
  CURLcode status = curl_global_init(CURL_GLOBAL_ALL);
  assert(CURLE_OK == status);

  CURL* curl = curl_easy_init();
  assert(curl);

  status = curl_easy_setopt(curl, CURLOPT_SSH_KNOWNHOSTS, "/tmp/khfile");
  assert(CURLE_OK == status);
}

curl/libcurl version

curl 7.63.0 (x86_64-pc-linux-gnu) libcurl/7.63.0 OpenSSL/1.1.1a zlib/1.2.11 libidn2/2.0.5 libssh/0.8.6/openssl/zlib
Release-Date: 2018-12-12
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp scp sftp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS Debug TrackMemory IDN IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP UnixSockets HTTPS-proxy