linux-kernel - Re: [PATCH] X.25: Fix address field length calculation

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Message-ID: <525E3925.7070105@datus.com>
Date:	Wed, 16 Oct 2013 06:58:46 +0000
From:	Kelleter, Günther <GKelleter@...us.com>
To:	Joe Perches <joe@...ches.com>
CC:	"andrew.hendry@...il.com" <andrew.hendry@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"linux-x25@...r.kernel.org" <linux-x25@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] X.25: Fix address field length calculation

Am 15.10.2013 19:29, schrieb Joe Perches:
> On Tue, 2013-10-15 at 14:29 +0000, Kelleter, Günther wrote:
>> Addresses are BCD encoded, not ASCII. x25_addr_ntoa got it right.
> []
>> Wrong length calculation leads to rejection of CALL ACCEPT packets.
> []
>> diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
> []
>> @@ -98,7 +98,7 @@ int x25_parse_address_block(struct sk_buff *skb,
>>  	}
>>   	len = *skb->data;
>> -	needed = 1 + (len >> 4) + (len & 0x0f);
>> +	needed = 1 + ((len >> 4) + (len & 0x0f) + 1) / 2;
> This calculation looks odd.
> Perhaps use bcd.h instead?
>

It's just the same calculation as in x25_add_ntoa (last line) and it's
used this way by x.25.
Two digits are encoded to one byte and the last byte is padded with 0 if
the total number of digits is odd.--
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