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Enno Gröper
Asked: 2016-05-21 06:10:31 +0800 CST

How to get a list of options, that can pushed to the clients?

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The OpenVPN manual currently only states:

This is a partial list of options which can currently be pushed: --route, --route-gateway, --route-delay, --redirect-gateway, --ip-win32, --dhcp-option, --inactive, --ping, --ping-exit, --ping-restart, --setenv, --persist-key, --persist-tun, --echo, --comp-lzo, --socket-flags, --sndbuf, --rcvbuf

But how do I get a complete list of options I can push to clients?

openvpn

1 Answers

  1. The generic way is to look through the code.

    The method pull_permission_mask of init.c contains a list of valid flags (cited here for the current 2.3 release):

    unsigned int flags =
      OPT_P_UP
    | OPT_P_ROUTE_EXTRAS
    | OPT_P_SOCKBUF
    | OPT_P_SOCKFLAGS
    | OPT_P_SETENV
    | OPT_P_SHAPER
    | OPT_P_TIMER
    | OPT_P_COMP
    | OPT_P_PERSIST
    | OPT_P_MESSAGES
    | OPT_P_EXPLICIT_NOTIFY
    | OPT_P_ECHO
    | OPT_P_PULL_MODE
    | OPT_P_PEER_ID;

    If --route-nopull is not set on client-side, the following flags are currently accepted additionally:

    flags |= (OPT_P_ROUTE | OPT_P_IPWIN32);

    Now we have to match this against the options from options.c. Each option, that has one of the flags above in its VERIFY_PERMISSION can theoretically be pushed to the client. of course there could be issues as with comp-lzo.

    As an example see the following snippet from options.c:

    else if (streq (p[0], "topology") && p[1])
    {
      VERIFY_PERMISSION (OPT_P_UP);
      options->topology = parse_topology (p[1], msglevel);
    }

    Since OPT_P_UP is in the list of flags above, "topology" may be pushed to clients.

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