Re: [Libevent-users] sendfile on solaris

[Nick Mathewson <nickm@xxxxxxxxxxxxx>]

On Thu, Aug 11, 2011 at 5:16 PM, Michael Herf <herf@xxxxxxxxx> wrote:
> In addition to my note about 64-bit offsets earlier:
>
> Solaris sendfile seems to fail when sending moderately large (<1GB) files.
> Not a 32/64 problem, but a buffer problem.
> Anyone else ever try this? It is definitely broken in http-server.c.
>
> It seems to be broken in the following way:
>    When sendfile sends partial data (EAGAIN, would block), "res" is always
> -1, rather than the amount sent.
>    Here's a patch that reads from the "offset" pointer instead to discover
> what was sent. This seems to work:
>
> --- buffer.c    2010-12-16 10:05:27.000000000 -0800
> +++ ../libevent/buffer.c        2011-08-11 14:13:42.288328799 -0700
> @@ -2262,11 +2262,18 @@
>        }
>        return (res);
>  #elif defined(SENDFILE_IS_SOLARIS)
> -       res = sendfile(fd, info->fd, &offset, chain->off);
> -       if (res == -1 && EVUTIL_ERR_RW_RETRIABLE(errno)) {
> +
> +       off_t offset0 = offset;
> +       res = sendfile(fd, info->fd, &offset, chain->off);
> +
> +       if (res == -1 && EVUTIL_ERR_RW_RETRIABLE(errno)) {
> +               if (offset - offset0) {
> +                       return offset - offset0;
> +               }
>                /* if this is EAGAIN or EINTR return 0; otherwise, -1 */
>                return (0);
> -       }
> +       }
> +
>        return (res);
>  #endif
>  }

Looks good; applying with a small tweak to make it fit the code style.
 Let me know if the patches-2.0 branch looks good to you now.

Also, you said elsewhere that you think this applies to the bsd
backends as well.  FWICT, it shouldn't: have a look at how the &len
variable is set and used there.

-- 
Nick
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