Subject: Re: [PATCH] ipv6: fix the bug when propagating Redirect Message

From: Duan Jiong <[email-masked]>
Date: Tue, 11 Dec 2012 20:58:20 +0800

于 2012/10/24 12:54, Steffen Klassert 写道:
> On Tue, Oct 23, 2012 at 11:26:25PM +0800, Duan Jiong wrote:
>>
>> Before using icmpv6_notify() to propagate redirect, change skb->data
>> to poing the IP packet that triggered the sending of the Redirect.
>>
>> Signed-off-by: Duan Jiong <[email-masked]>
>> ---
>>  net/ipv6/ndisc.c |   39 +++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 39 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
>> index ff36194..0f73303 100644
>> --- a/net/ipv6/ndisc.c
>> +++ b/net/ipv6/ndisc.c
>> @@ -1334,6 +1334,11 @@ out:
>>  
>>  static void ndisc_redirect_rcv(struct sk_buff *skb)
>>  {
>> +	int opt_len;
>> +	int opt_offset;
>> +	int ndisc_head_len;
>> +	struct nd_opt_hdr *nd_opt;
>> +	
>>  #ifdef CONFIG_IPV6_NDISC_NODETYPE
>>  	switch (skb->ndisc_nodetype) {
>>  	case NDISC_NODETYPE_HOST:
>> @@ -1350,6 +1355,40 @@ static void ndisc_redirect_rcv(struct sk_buff *skb)
>>  		return;
>>  	}
>>  
>> +	ndisc_head_len = sizeof(struct icmp6hdr) + 2*sizeof(struct in6_addr);
>> +	if (!pskb_may_pull(skb, ndisc_head_len)) {
>> +		return;
>> +	}
>> +
>> +	nd_opt = (struct nd_opt_hdr *)(skb->data + ndisc_head_len);
>> +
>> +	opt_len = skb->tail - skb->transport_header - ndisc_head_len;
>> +	if (opt_len < 0) {
>> +		return;
>> +	}
>> +	while (opt_len) {
>> +		int l;
>> +	
>> +		if (opt_len < sizeof(struct nd_opt_hdr)) {
>> +			return;
>> +		}
>> +		l = nd_opt->nd_opt_len << 3;
>> +		if (opt_len < l || l == 0) {
>> +			return;
>> +		}
>> +		if (nd_opt->nd_opt_type == ND_OPT_REDIRECT_HDR) {
>> +			__skb_pull(skb, ndisc_head_len + opt_offset + 8);
>> +			break;
>> +		}
>> +		opt_len -= l;
>> +		nd_opt = ((void *)nd_opt) + 1;
>> +		opt_offset += 1;
>> +	}
> 
> Instead of the above loop, you could use ndisc_parse_options().
> This does the same what you are doing here and it would make it
> a bit clearer what's going on.
> 
I apologize for not replying to you earlier,and i will continue 
to update my patches. 

Just like you said, i try to use ndisc_parse_options() to instead
of the loop, but i find the skb->data can't be changed in function
ndisc_parse_options() due to lack of  arguments. So i think it is
better to continue to use the loop. How do you think this?

Thanks!