svn commit: r252532 - stable/9/sys/kern

[Lawrence Stewart]

On 07/03/13 13:36, Lawrence Stewart wrote:
> Author: lstewart
> Date: Wed Jul  3 03:36:36 2013
> New Revision: 252532
> URL: http://svnweb.freebsd.org/changeset/base/252532
> 
> Log:

    MFC r251984:

>   When a previous call to sbsndptr() leaves sb->sb_sndptroff at the start of an
>   mbuf that was fully consumed by the previous call, the mbuf ptr returned by the
>   current call ends up being the previous mbuf in the sb chain to the one that
>   contains the data we want.
>   
>   This does not cause any observable issues because the mbuf copy routines happily
>   walk the mbuf chain to get to the data at the moff offset, which in this case
>   means they effectively skip over the mbuf returned by sbsndptr().
>   
>   We can't adjust sb->sb_sndptr during the previous call for this case because the
>   next mbuf in the chain may not exist yet. We therefore need to detect the
>   condition and make the adjustment during the current call.
>   
>   Fix by detecting the special case of moff being at the start of the next mbuf in
>   the chain and adjust the required accounting variables accordingly.
>   
>   Reviewed by:	andre