[PATCH 5/7] dix: Extend initial connection handshake for forwarding proxies

[walter harms]

Am 20.09.2012 22:56, schrieb Adam Jackson:
> Forwarding proxies like sshd will appear to be local, even though they
> aren't really.  This leads to weird behaviour for extensions that truly
> require running under the same OS services as the client, like MIT-SHM
> and DRI2.
> 
> Add two new legal values for the initial connection's byteOrder field,
> 'r' and 'R'.  These act like 'l' and 'B' respectively, but have the side
> effect of forcing the client to be treated as non-local.  Forwarding
> proxies should attempt to munge the first packet of the connection
> accordingly; older servers will reject connections thusly munged, so the
> proxy should fall back to passthrough if the munged connection attempt
> fails.
> 
> Reviewed-by: Daniel Stone <daniel at fooishbar.org>
> Signed-off-by: Adam Jackson <ajax at redhat.com>
> ---
>  dix/dispatch.c  |   19 ++++++++++++-------
>  os/connection.c |   10 +++++-----
>  2 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/dix/dispatch.c b/dix/dispatch.c
> index 0ce10c2..2df1a6e 100644
> --- a/dix/dispatch.c
> +++ b/dix/dispatch.c
> @@ -3499,14 +3499,16 @@ ProcInitialConnection(ClientPtr client)
>      REQUEST(xReq);
>      xConnClientPrefix *prefix;
>      int whichbyte = 1;
> +    char order;
>  
> -    prefix = (xConnClientPrefix *) ((char *) stuff + sz_xReq);
> -    if ((prefix->byteOrder != 'l') && (prefix->byteOrder != 'B'))
> -        return client->noClientException = -1;
> -    if (((*(char *) &whichbyte) && (prefix->byteOrder == 'B')) ||
> -        (!(*(char *) &whichbyte) && (prefix->byteOrder == 'l'))) {
> -        client->swapped = TRUE;
> -        SwapConnClientPrefix(prefix);
> +    prefix = (xConnClientPrefix *) ((char *)stuff + sz_xReq);
> +    order = prefix->byteOrder;
> +    if (order != 'l' && order != 'B' && order != 'r' && order != 'R')
> +	return client->noClientException = -1;
> +    if (((*(char *) &whichbyte) && (order == 'B' || order == 'R')) ||
> +	(!(*(char *) &whichbyte) && (order == 'l' || order == 'r'))) {
> +	client->swapped = TRUE;
> +	SwapConnClientPrefix(prefix);
>      }

this is hard to read, is it possible to have *(char *) &whichbyte in a tmp var ?

re,
 wh

>      stuff->reqType = 2;
>      stuff->length += bytes_to_int32(prefix->nbytesAuthProto) +
> @@ -3514,6 +3516,9 @@ ProcInitialConnection(ClientPtr client)
>      if (client->swapped) {
>          swaps(&stuff->length);
>      }
> +    if (order == 'r' || order == 'R') {
> +	client->local = FALSE;
> +    }
>      ResetCurrentRequest(client);
>      return Success;
>  }
> diff --git a/os/connection.c b/os/connection.c
> index d27116a..4561caa 100644
> --- a/os/connection.c
> +++ b/os/connection.c
> @@ -894,7 +894,7 @@ ErrorConnMax(XtransConnInfo trans_conn)
>      xConnSetupPrefix csp;
>      char pad[3] = { 0, 0, 0 };
>      struct iovec iov[3];
> -    char byteOrder = 0;
> +    char order = 0;
>      int whichbyte = 1;
>      struct timeval waittime;
>      fd_set mask;
> @@ -907,15 +907,15 @@ ErrorConnMax(XtransConnInfo trans_conn)
>      FD_SET(fd, &mask);
>      (void) Select(fd + 1, &mask, NULL, NULL, &waittime);
>      /* try to read the byte-order of the connection */
> -    (void) _XSERVTransRead(trans_conn, &byteOrder, 1);
> -    if ((byteOrder == 'l') || (byteOrder == 'B')) {
> +    (void) _XSERVTransRead(trans_conn, &order, 1);
> +    if (order == 'l' || order == 'B' || order == 'r' || order == 'R') {
>          csp.success = xFalse;
>          csp.lengthReason = sizeof(NOROOM) - 1;
>          csp.length = (sizeof(NOROOM) + 2) >> 2;
>          csp.majorVersion = X_PROTOCOL;
>          csp.minorVersion = X_PROTOCOL_REVISION;
> -        if (((*(char *) &whichbyte) && (byteOrder == 'B')) ||
> -            (!(*(char *) &whichbyte) && (byteOrder == 'l'))) {
> +	if (((*(char *) &whichbyte) && (order == 'B' || order == 'R')) ||
> +	    (!(*(char *) &whichbyte) && (order == 'l' || order == 'r'))) {
>              swaps(&csp.majorVersion);
>              swaps(&csp.minorVersion);
>              swaps(&csp.length);