Re: Bug on CCID 3 of DCCP

[Gerrit Renker <gerrit@xxxxxxxxxxxxxx>]

Hi Ian,
| Would suggest that patch is worth pushing upstreams then as quickly as we can...
| 
I went through the code again and found that X_calc = 0 does not cause harm, due
to clamping to s/t_mbi. My suggestion is to remove this BUG_ON and to test instead
if t_ipi = 0 (since this would allow flooding of network).

Patch is in the next email, test tree has been updated, also CCID-4 has now
the same change (removed X_calc BUG_ON, added t_ipi==0 BUG_ON).

Gerrit

| On 21 February 2012 15:05, Gerrit Renker <gerrit@xxxxxxxxxxxxxx> wrote:
| >
| > Here is a patch that can be used in place of enabling the debug messages.
| > It may be easier to use this, especially if it takes long to reproduce the
| > bug.
| >
| > From a quick look it seems that x_calc = 0 will do no harm in the old
| > code, since
| > ccid3_hc_tx_update_x() is called subsequently, it will set x to s/t_mbi
| >
| > --- a/net/dccp/ccids/ccid3.c
| > +++ b/net/dccp/ccids/ccid3.c
| > @@ -237,7 +237,11 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned
| > long data)
| >                 *
| >                 *  Note that X_recv is scaled by 2^6 while X_calc is not
| >                 */
| > -               BUG_ON(hc->tx_p && !hc->tx_x_calc);
| > +               if (hc->tx_p && !hc->tx_x_calc)
| > +                       DCCP_CRIT("ERROR: s=%u, p=%u, x_calc = %u, x_recv
| > = %llu, X = %llu",
| > +                               hc->tx_s, hc->tx_p, hc->tx_x_calc,
| > +                               (unsigned long long)hc->tx_x_recv,
| > +                               (unsigned long long)hc->tx_x);
| >
| >                if (hc->tx_x_calc > (hc->tx_x_recv >> 5))
| >                        hc->tx_x_recv =
| > --
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