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From:   "Gix, Brian" <brian.gix@intel.com>
To:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
CC:     "Stotland, Inga" <inga.stotland@intel.com>,
        "jakub.witowski@silvair.com" <jakub.witowski@silvair.com>,
        "michal.lowas-rzechonek@silvair.com" 
        <michal.lowas-rzechonek@silvair.com>
Subject: RE: [PATCH BlueZ] mesh: Fix long MIC usage in segmented messages
Thread-Topic: [PATCH BlueZ] mesh: Fix long MIC usage in segmented messages
Thread-Index: AQHVEZBzEH3OQE0cFU+dUfs5UeuEwaZ4/rtw
Date:   Thu, 23 May 2019 17:58:13 +0000
Message-ID: <DEBB0CAA2616974FAE35E4B560B9A4376CB5FA78@ORSMSX103.amr.corp.intel.com>
References: <20190523175321.13094-1-brian.gix@intel.com>
In-Reply-To: <20190523175321.13094-1-brian.gix@intel.com>
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Hi Jakub and Michal,

If you have no objections, this will be the version of the Long MIC patch I will be applying.

> -----Original Message-----
> From: Gix, Brian
> Sent: Thursday, May 23, 2019 10:53 AM
> To: linux-bluetooth@vger.kernel.org
> Cc: Stotland, Inga <inga.stotland@intel.com>; Gix, Brian
> <brian.gix@intel.com>; jakub.witowski@silvair.com; michal.lowas-
> rzechonek@silvair.com
> Subject: [PATCH BlueZ] mesh: Fix long MIC usage in segmented messages
> 
> From: Jakub Witowski <jakub.witowski@silvair.com>
> 
> Contrary to the comment, implementation used a 8-byte MIC even if this
> generated an additional segment.
> ---
>  mesh/model.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mesh/model.c b/mesh/model.c index 034d54496..90bb62db8
> 100644
> --- a/mesh/model.c
> +++ b/mesh/model.c
> @@ -40,6 +40,9 @@
>  #include "mesh/util.h"
>  #include "mesh/model.h"
> 
> +/* Divide and round to ceiling (up) to calculate segment count */
> +#define CEILDIV(val, div) (((val) + (div) - 1) / (div))
> +
>  struct mesh_model {
>  	const struct mesh_model_ops *cbs;
>  	void *user_data;
> @@ -451,7 +454,7 @@ static bool msg_send(struct mesh_node *node, bool
> credential, uint16_t src,
> 
>  	/* Use large MIC if it doesn't affect segmentation */
>  	if (msg_len > 11 && msg_len <= 376) {
> -		if ((out_len / 12) == ((out_len + 4) / 12)) {
> +		if (CEILDIV(out_len, 12) == CEILDIV(out_len + 4, 12)) {
>  			szmic = true;
>  			out_len = msg_len + sizeof(uint64_t);
>  		}
> --
> 2.14.5