[PATCH] Events: fixed EPOLLRDHUP with FIONREAD (ticket #2367)

[Maxim Dounin]

Hello!

On Fri, Jul 15, 2022 at 03:23:57PM +0300, Maxim Dounin wrote:

> # HG changeset patch
> # User Maxim Dounin <mdounin at mdounin.ru>
> # Date 1657887572 -10800
> #      Fri Jul 15 15:19:32 2022 +0300
> # Node ID f3510cb959d1ae168e3458036d1606dcedffd212
> # Parent  ae2d62bb12c00ebd014c147d7b37252ccfe72373
> Events: fixed EPOLLRDHUP with FIONREAD (ticket #2367).
> 
> When reading exactly rev->available bytes, rev->available might become 0
> after FIONREAD usage introduction in efd71d49bde0.  On the next call of
> ngx_readv_chain() on systems with EPOLLRDHUP this resulted in return without
> any actions, that is, with rev->ready set, and this in turn resulted in no
> timers set in event pipe, leading to socket leaks.
> 
> Fix is to reset rev->ready in ngx_readv_chain() when returning due to
> rev->available being 0 with EPOLLRDHUP, much like it is already done in
> ngx_unix_recv().  This ensures that if rev->available will become 0, on
> systems with EPOLLRDHUP support appropriate EPOLLRDHUP-specific handling
> will happen on the next ngx_readv_chain() call.
> 
> While here, also synced ngx_readv_chain() to match ngx_unix_recv() and
> reset rev->ready when returning due to rev->available being 0 with kqueue.
> This is mostly cosmetic change, as rev->ready is anyway reset when
> rev->available is set to 0.
> 
> diff --git a/src/os/unix/ngx_readv_chain.c b/src/os/unix/ngx_readv_chain.c
> --- a/src/os/unix/ngx_readv_chain.c
> +++ b/src/os/unix/ngx_readv_chain.c
> @@ -46,6 +46,7 @@ ngx_readv_chain(ngx_connection_t *c, ngx
>                  return 0;
>  
>              } else {
> +                rev->ready = 0;
>                  return NGX_AGAIN;
>              }
>          }
> @@ -63,6 +64,7 @@ ngx_readv_chain(ngx_connection_t *c, ngx
>                         rev->pending_eof, rev->available);
>  
>          if (rev->available == 0 && !rev->pending_eof) {
> +            rev->ready = 0;
>              return NGX_AGAIN;
>          }
>      }

Already reviewed in #2367 comments, pushed to 
http://mdounin.ru/hg/nginx/.

-- 
Maxim Dounin
http://mdounin.ru/