Re: [PATCH] tcp: Pass union tcp_conn pointer to destroy and splice timer functions

[David Gibson <david@gibson.dropbear.id.au>]

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On Sat, Nov 19, 2022 at 09:39:29AM +0100, Stefano Brivio wrote:
> The pointers are actually the same, but we later pass the container
> union to tcp_table_compact(), which might zero the size of the whole
> union, and this confuses Coverity Scan.
> 
> Given that we have pointers to the container union to start with,
> just pass those instead, all the way down to tcp_table_compact().
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tcp.c        | 17 +++++++++--------
>  tcp_conn.h   |  4 ++--
>  tcp_splice.c | 16 ++++++++++------
>  3 files changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 8874789..ff12dfa 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -1376,16 +1376,18 @@ void tcp_table_compact(struct ctx *c, union tcp_conn *hole)
>  /**
>   * tcp_conn_destroy() - Close sockets, trigger hash table removal and compaction
>   * @c:		Execution context
> - * @conn:	Connection pointer
> + * @conn_union:	Connection pointer (container union)
>   */
> -static void tcp_conn_destroy(struct ctx *c, struct tcp_tap_conn *conn)
> +static void tcp_conn_destroy(struct ctx *c, union tcp_conn *conn_union)
>  {
> +	struct tcp_tap_conn *conn = &conn_union->tap;
> +
>  	close(conn->sock);
>  	if (conn->timer != -1)
>  		close(conn->timer);
>  
>  	tcp_hash_remove(c, conn);
> -	tcp_table_compact(c, (union tcp_conn *)conn);
> +	tcp_table_compact(c, conn_union);
>  }
>  
>  static void tcp_rst_do(struct ctx *c, struct tcp_tap_conn *conn);
> @@ -1535,13 +1537,12 @@ void tcp_defer_handler(struct ctx *c)
>  	for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
>  		if (conn->c.spliced) {
>  			if (conn->splice.flags & CLOSING)
> -				tcp_splice_destroy(c, &conn->splice);
> +				tcp_splice_destroy(c, conn);
>  		} else {
>  			if (conn->tap.events == CLOSED)
> -				tcp_conn_destroy(c, &conn->tap);
> +				tcp_conn_destroy(c, conn);
>  		}
>  	}
> -
>  }
>  
>  /**
> @@ -3395,10 +3396,10 @@ void tcp_timer(struct ctx *c, const struct timespec *ts)
>  
>  	for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
>  		if (conn->c.spliced) {
> -			tcp_splice_timer(c, &conn->splice);
> +			tcp_splice_timer(c, conn);
>  		} else {
>  			if (conn->tap.events == CLOSED)
> -				tcp_conn_destroy(c, &conn->tap);
> +				tcp_conn_destroy(c, conn);
>  		}
>  	}
>  
> diff --git a/tcp_conn.h b/tcp_conn.h
> index 4a8be29..a146276 100644
> --- a/tcp_conn.h
> +++ b/tcp_conn.h
> @@ -181,8 +181,8 @@ extern union tcp_conn tc[];
>  
>  void tcp_splice_conn_update(struct ctx *c, struct tcp_splice_conn *new);
>  void tcp_table_compact(struct ctx *c, union tcp_conn *hole);
> -void tcp_splice_destroy(struct ctx *c, struct tcp_splice_conn *conn);
> -void tcp_splice_timer(struct ctx *c, struct tcp_splice_conn *conn);
> +void tcp_splice_destroy(struct ctx *c, union tcp_conn *conn_union);
> +void tcp_splice_timer(struct ctx *c, union tcp_conn *conn_union);
>  void tcp_splice_pipe_refill(const struct ctx *c);
>  
>  
> diff --git a/tcp_splice.c b/tcp_splice.c
> index e2f0ce1..72b1672 100644
> --- a/tcp_splice.c
> +++ b/tcp_splice.c
> @@ -251,10 +251,12 @@ void tcp_splice_conn_update(struct ctx *c, struct tcp_splice_conn *new)
>  /**
>   * tcp_splice_destroy() - Close spliced connection and pipes, clear
>   * @c:		Execution context
> - * @conn:	Connection pointer
> + * @conn_union:	Spliced connection (container union)
>   */
> -void tcp_splice_destroy(struct ctx *c, struct tcp_splice_conn *conn)
> +void tcp_splice_destroy(struct ctx *c, union tcp_conn *conn_union)
>  {
> +	struct tcp_splice_conn *conn = &conn_union->splice;
> +
>  	if (conn->events & SPLICE_ESTABLISHED) {
>  		/* Flushing might need to block: don't recycle them. */
>  		if (conn->pipe_a_b[0] != -1) {
> @@ -283,7 +285,7 @@ void tcp_splice_destroy(struct ctx *c, struct tcp_splice_conn *conn)
>  	debug("TCP (spliced): index %li, CLOSED", CONN_IDX(conn));
>  
>  	c->tcp.splice_conn_count--;
> -	tcp_table_compact(c, (union tcp_conn *)conn);
> +	tcp_table_compact(c, conn_union);
>  }
>  
>  /**
> @@ -824,12 +826,14 @@ void tcp_splice_init(struct ctx *c)
>  /**
>   * tcp_splice_timer() - Timer for spliced connections
>   * @c:		Execution context
> - * @conn:	Spliced connection
> + * @conn_union:	Spliced connection (container union)
>   */
> -void tcp_splice_timer(struct ctx *c, struct tcp_splice_conn *conn)
> +void tcp_splice_timer(struct ctx *c, union tcp_conn *conn_union)
>  {
> +	struct tcp_splice_conn *conn = &conn_union->splice;
> +
>  	if (conn->flags & CLOSING) {
> -		tcp_splice_destroy(c, conn);
> +		tcp_splice_destroy(c, conn_union);
>  		return;
>  	}
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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