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

From: Steffen Klassert <[email-masked]>
Date: Tue, 11 Dec 2012 14:45:14 +0100

On Tue, Dec 11, 2012 at 08:58:20PM +0800, Duan Jiong wrote:
> 
> 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?
> 

You can change the data pointer after ndisc_parse_options().
Something like the (untested) patch below should do it.

 include/net/ndisc.h |    7 +++++++
 net/ipv6/ndisc.c    |   20 ++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/net/ndisc.h b/include/net/ndisc.h
index 980d263..c17bccd 100644
--- a/include/net/ndisc.h
+++ b/include/net/ndisc.h
@@ -78,6 +78,13 @@ struct ra_msg {
 	__be32			retrans_timer;
 };
 
+struct rd_msg {
+        struct icmp6hdr	icmph;
+        struct in6_addr	target;
+        struct in6_addr	dest;
+	__u8		opt[0];
+};
+
 struct nd_opt_hdr {
 	__u8		nd_opt_type;
 	__u8		nd_opt_len;
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 2edce30..9afd23f 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1333,6 +1333,12 @@ out:
 
 static void ndisc_redirect_rcv(struct sk_buff *skb)
 {
+	u8 *hdr;
+	struct ndisc_options ndopts;
+	struct rd_msg *msg = (struct rd_msg *) skb_transport_header(skb);
+	u32 ndoptlen = skb->tail - (skb->transport_header +
+				    offsetof(struct rd_msg, opt));
+
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
 	switch (skb->ndisc_nodetype) {
 	case NDISC_NODETYPE_HOST:
@@ -1349,6 +1355,20 @@ static void ndisc_redirect_rcv(struct sk_buff *skb)
 		return;
 	}
 
+	if (!ndisc_parse_options(msg->opt, ndoptlen, &ndopts)) {
+		ND_PRINTK(2, warn, "Redirect: invalid ND options\n");
+		return;
+	}
+
+	if (!ndopts.nd_opts_rh)
+		return;
+
+	hdr = (u8 *) ndopts.nd_opts_rh;
+	hdr += 8;
+
+	if (!pskb_pull(skb, hdr - skb_transport_header(skb)))
+		return;
+
 	icmpv6_notify(skb, NDISC_REDIRECT, 0, 0);
 }
 
-- 
1.7.9.5