On Mon, Feb 27, 2023 at 11:00:03AM +0100, Stefano Brivio wrote:
> ...and, given that I keep getting this wrong, add a convenience
> macro, MAX_FROM_BITS().
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

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

> ---
>  passt.h    | 4 ++--
>  tcp.h      | 4 ++--
>  tcp_conn.h | 2 +-
>  util.h     | 2 ++
>  4 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/passt.h b/passt.h
> index 3d7e567..e0383eb 100644
> --- a/passt.h
> +++ b/passt.h
> @@ -42,7 +42,7 @@ union epoll_ref;
>  /**
>   * union epoll_ref - Breakdown of reference for epoll socket bookkeeping
>   * @proto:	IP protocol number
> - * @s:		Socket number (implies 2^24 limit on number of descriptors)
> + * @s:		Socket number (implies 2^24-1 limit on number of descriptors)
>   * @tcp:	TCP-specific reference part
>   * @udp:	UDP-specific reference part
>   * @icmp:	ICMP-specific reference part
> @@ -53,7 +53,7 @@ union epoll_ref {
>  	struct {
>  		int32_t		proto:8,
>  #define SOCKET_REF_BITS		24
> -#define SOCKET_MAX		(1 << SOCKET_REF_BITS)
> +#define SOCKET_MAX		MAX_FROM_BITS(SOCKET_REF_BITS)
>  				s:SOCKET_REF_BITS;
>  		union {
>  			union tcp_epoll_ref tcp;
> diff --git a/tcp.h b/tcp.h
> index 5527c5b..36e5391 100644
> --- a/tcp.h
> +++ b/tcp.h
> @@ -8,8 +8,8 @@
>  
>  #define TCP_TIMER_INTERVAL		1000	/* ms */
>  
> -#define TCP_CONN_INDEX_BITS		17	/* 128k */
> -#define TCP_MAX_CONNS			(1 << TCP_CONN_INDEX_BITS)
> +#define TCP_CONN_INDEX_BITS		17	/* 128k - 1 */
> +#define TCP_MAX_CONNS			MAX_FROM_BITS(TCP_CONN_INDEX_BITS)
>  
>  struct ctx;
>  
> diff --git a/tcp_conn.h b/tcp_conn.h
> index a499f34..c22632b 100644
> --- a/tcp_conn.h
> +++ b/tcp_conn.h
> @@ -54,7 +54,7 @@ struct tcp_tap_conn {
>  
>  #define TCP_RETRANS_BITS		3
>  	unsigned int	retrans		:TCP_RETRANS_BITS;
> -#define TCP_MAX_RETRANS			((1U << TCP_RETRANS_BITS) - 1)
> +#define TCP_MAX_RETRANS			MAX_FROM_BITS(TCP_RETRANS_BITS)
>  
>  #define TCP_WS_BITS			4	/* RFC 7323 */
>  #define TCP_WS_MAX			14
> diff --git a/util.h b/util.h
> index 6303c17..570094c 100644
> --- a/util.h
> +++ b/util.h
> @@ -40,6 +40,8 @@
>  #define ROUND_DOWN(x, y)	((x) & ~((y) - 1))
>  #define ROUND_UP(x, y)		(((x) + (y) - 1) & ~((y) - 1))
>  
> +#define MAX_FROM_BITS(n)	((int)((1U << (n)) - 1))
> +
>  #define BIT(n)			(1UL << (n))
>  #define BITMAP_BIT(n)		(BIT((n) % (sizeof(long) * 8)))
>  #define BITMAP_WORD(n)		(n / (sizeof(long) * 8))

-- 
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