netdev - Re: [PATCH] IPv6: Fix the data length of get destination options with short length

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Message-ID: <483E151B.2000804@cn.fujitsu.com>
Date:	Thu, 29 May 2008 10:29:47 +0800
From:	Yang Hongyang <yanghy@...fujitsu.com>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
CC:	davem@...set.davemloft.net,
	FNST-Wei Yongjun <yjwei@...fujitsu.com>,
	netdev@...r.kernel.org, Wang Chen <wangchen@...fujitsu.com>
Subject: Re: [PATCH] IPv6: Fix the data length of get destination options
 with short length

YOSHIFUJI Hideaki / 吉藤英明 wrote:

> POSIX says that the object pointed to by the option_len argument shall be
> modified to indicate the actual length of the value.
> Do you think this change conforms to the spec?
> 

We use the codes below to get the destination options,the length cnt is half of the option length.
	cnt = sizeof(incmsg) / 2;
	if (getsockopt(sk, IPPROTO_IPV6, IPV6_DSTOPTS,
		       (char *)incmsg, &cnt) == -1) 

We can see from net/ipv6/ipv6_sockglue.c,the code below store half of the option length to incmsg,
so the acture data length of incmsg is half of the option length.According to RFC(as you said 
"option_len argument shall be modified to indicate the actual length of the value") the cnt 
should specify the data length of incmsg,that is half of the option length.So we should return len 
instead of ipv6_optlen(hdr).
 832         len = min_t(unsigned int, len, ipv6_optlen(hdr));
 833         if (copy_to_user(optval, hdr, len))
 834                 return -EFAULT;


-- 
Regards
Yang Hongyang
 
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