[PATCH v2] ipv6: Change skb->data before using icmpv6_notify() to propagate redirect

[Duan Jiong <djduanjiong@gmail.com>]

In function ndisc_redirect_rcv(), the skb->data points to the transport
header, but function icmpv6_notify() need the skb->data points to the
inner IP packet. So before using icmpv6_notify() to propagate redirect,
change skb->data to point the inner IP packet that triggered the sending
of the Redirect, and introduce struct rd_msg to make it easy.

Many thanks to Steffen Klassert.

Signed-off-by: Duan Jiong <djduanjiong@gmail.com>
---
 include/net/ndisc.h |    7 +++++++
 net/ipv6/ndisc.c    |   22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/include/net/ndisc.h b/include/net/ndisc.h
index 980d263..6b305d7 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..03deabc 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 +1355,22 @@ 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);
 }
 
-- 
1.7.1