Re: [Openvpn-devel] [PATCH] Set the correct mtu on windows based systems

[Christopher S. <cs...@ma...>]

Hi,

what do you think about this patch? Is anything missing?

Best regards

Christopher

On 4/4/19 1:16 PM, Christopher Schenk wrote:
> Signed-off-by: Christopher Schenk <cs...@ma...>
> ---
>   include/openvpn-msg.h         |  8 ++++
>   src/openvpn/tun.c             | 89 +++++++++++++++++++++++++++++++++++
>   src/openvpnserv/interactive.c | 31 ++++++++++++
>   3 files changed, 128 insertions(+)
>
> diff --git a/include/openvpn-msg.h b/include/openvpn-msg.h
> index 66177a21..10cd68ac 100644
> --- a/include/openvpn-msg.h
> +++ b/include/openvpn-msg.h
> @@ -39,6 +39,7 @@ typedef enum {
>       msg_del_block_dns,
>       msg_register_dns,
>       msg_enable_dhcp,
> +    msg_set_mtu,
>   } message_type_t;
>   
>   typedef struct {
> @@ -117,4 +118,11 @@ typedef struct {
>       interface_t iface;
>   } enable_dhcp_message_t;
>   
> +typedef struct {
> +    message_header_t header;
> +    interface_t iface;
> +    short family;
> +    int mtu;
> +} set_mtu_message_t;
> +
>   #endif /* ifndef OPENVPN_MSG_H_ */
> diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
> index 48a8fdf7..3895e421 100644
> --- a/src/openvpn/tun.c
> +++ b/src/openvpn/tun.c
> @@ -69,6 +69,10 @@ static void netsh_ifconfig(const struct tuntap_options *to,
>                              const in_addr_t netmask,
>                              const unsigned int flags);
>   
> +static void windows_set_mtu(const int iface_index,
> +                            const short family,
> +                            const int mtu);
> +
>   static void netsh_set_dns6_servers(const struct in6_addr *addr_list,
>                                      const int addr_len,
>                                      const char *flex_name);
> @@ -201,6 +205,47 @@ out:
>       return ret;
>   }
>   
> +static bool
> +do_set_mtu_service(const struct tuntap *tt, const short family, const int mtu)
> +{
> +    DWORD len;
> +    bool ret = false;
> +    ack_message_t ack;
> +    struct gc_arena gc = gc_new();
> +    HANDLE pipe = tt->options.msg_channel;
> +    const char *family_name = (family == AF_INET6) ? "IPv6" : "IPv4";
> +    set_mtu_message_t mtu_msg = {
> +        .header = {
> +            msg_set_mtu,
> +            sizeof(set_mtu_message_t),
> +            0
> +        },
> +        .iface = {.index = tt->adapter_index,.name = tt->actual_name },
> +        .mtu = mtu,
> +        .family = family
> +    };
> +
> +    if (!send_msg_iservice(pipe, &mtu_msg, sizeof(mtu_msg), &ack, "Set_mtu"))
> +    {
> +        goto out;
> +    }
> +
> +    if (ack.error_number != NO_ERROR)
> +    {
> +        msg(M_NONFATAL, "TUN: setting %s mtu using service failed: %s [status=%u if_index=%d]",
> +            family_name, strerror_win32(ack.error_number, &gc), ack.error_number, mtu_msg.iface.index);
> +    }
> +    else
> +    {
> +        msg(M_INFO, "%s MTU set to %d on interface %d using service", family_name, mtu, mtu_msg.iface.index);
> +        ret = true;
> +    }
> +
> +out:
> +    gc_free(&gc);
> +    return ret;
> +}
> +
>   #endif /* ifdef _WIN32 */
>   
>   #ifdef TARGET_SOLARIS
> @@ -984,6 +1029,7 @@ do_ifconfig_ipv6(struct tuntap *tt, const char *ifname, int tun_mtu,
>       {
>           do_address_service(true, AF_INET6, tt);
>           do_dns6_service(true, tt);
> +        do_set_mtu_service(tt, AF_INET6, tun_mtu);
>       }
>       else
>       {
> @@ -1000,6 +1046,7 @@ do_ifconfig_ipv6(struct tuntap *tt, const char *ifname, int tun_mtu,
>           netsh_command(&argv, 4, M_FATAL);
>           /* set ipv6 dns servers if any are specified */
>           netsh_set_dns6_servers(tt->options.dns6, tt->options.dns6_len, ifname);
> +        windows_set_mtu(tt->adapter_index, AF_INET6, tun_mtu);
>       }
>   
>       /* explicit route needed */
> @@ -1394,6 +1441,14 @@ do_ifconfig_ipv4(struct tuntap *tt, const char *ifname, int tun_mtu,
>   
>                   break;
>           }
> +        if (tt->options.msg_channel)
> +        {
> +            do_set_mtu_service(tt, AF_INET, tun_mtu);
> +        }
> +        else
> +        {
> +            windows_set_mtu(tt->adapter_index, AF_INET, tun_mtu);
> +        }
>       }
>   
>   #else  /* if defined(TARGET_LINUX) */
> @@ -5236,6 +5291,40 @@ out:
>       return ret;
>   }
>   
> +static void
> +windows_set_mtu(const int iface_index, const short family,
> +                const int mtu)
> +{
> +    DWORD err = 0;
> +    struct gc_arena gc = gc_new();
> +    MIB_IPINTERFACE_ROW ipiface;
> +    InitializeIpInterfaceEntry(&ipiface);
> +    const char *family_name = (family == AF_INET6) ? "IPv6" : "IPv4";
> +    ipiface.Family = family;
> +    ipiface.InterfaceIndex = iface_index;
> +    err = GetIpInterfaceEntry(&ipiface);
> +    if (err == NO_ERROR)
> +    {
> +        if (family == AF_INET)
> +        {
> +            ipiface.SitePrefixLength = 0;
> +        }
> +        ipiface.NlMtu = mtu;
> +        err = SetIpInterfaceEntry(&ipiface);
> +    }
> +
> +    if (err != NO_ERROR)
> +    {
> +        msg(M_WARN, "TUN: Setting %s mtu failed: %s [status=%u if_index=%d]",
> +            family_name, strerror_win32(err, &gc), err, iface_index);
> +    }
> +    else
> +    {
> +        msg(M_INFO, "Successfully set %s mtu on interface %d", family_name, iface_index);
> +    }
> +}
> +
> +
>   /*
>    * Return a TAP name for netsh commands.
>    */
> diff --git a/src/openvpnserv/interactive.c b/src/openvpnserv/interactive.c
> index 623c3ff7..c24cb22b 100644
> --- a/src/openvpnserv/interactive.c
> +++ b/src/openvpnserv/interactive.c
> @@ -1198,6 +1198,29 @@ HandleEnableDHCPMessage(const enable_dhcp_message_t *dhcp)
>       return err;
>   }
>   
> +static DWORD
> +HandleMTUMessage(const set_mtu_message_t *mtu)
> +{
> +    DWORD err = 0;
> +    MIB_IPINTERFACE_ROW ipiface;
> +    InitializeIpInterfaceEntry(&ipiface);
> +    ipiface.Family = mtu->family;
> +    ipiface.InterfaceIndex = mtu->iface.index;
> +    err = GetIpInterfaceEntry(&ipiface);
> +    if (err != NO_ERROR)
> +    {
> +        return err;
> +    }
> +    if (mtu->family == AF_INET)
> +    {
> +        ipiface.SitePrefixLength = 0;
> +    }
> +    ipiface.NlMtu = mtu->mtu;
> +
> +    err = SetIpInterfaceEntry(&ipiface);
> +    return err;
> +}
> +
>   static VOID
>   HandleMessage(HANDLE pipe, DWORD bytes, DWORD count, LPHANDLE events, undo_lists_t *lists)
>   {
> @@ -1210,6 +1233,7 @@ HandleMessage(HANDLE pipe, DWORD bytes, DWORD count, LPHANDLE events, undo_lists
>           block_dns_message_t block_dns;
>           dns_cfg_message_t dns;
>           enable_dhcp_message_t dhcp;
> +        set_mtu_message_t mtu;
>       } msg;
>       ack_message_t ack = {
>           .header = {
> @@ -1277,6 +1301,13 @@ HandleMessage(HANDLE pipe, DWORD bytes, DWORD count, LPHANDLE events, undo_lists
>               }
>               break;
>   
> +        case msg_set_mtu:
> +            if (msg.header.size == sizeof(msg.mtu))
> +            {
> +                ack.error_number = HandleMTUMessage(&msg.mtu);
> +            }
> +            break;
> +
>           default:
>               ack.error_number = ERROR_MESSAGE_TYPE;
>               MsgToEventLog(MSG_FLAGS_ERROR, TEXT("Unknown message type %d"), msg.header.type);