[PATCH 3.12 46/88] sit: correct IP protocol used in ipip6_err

From: Jiri Slaby
Date: Thu Jul 14 2016 - 04:30:47 EST

From: Simon Horman <simon.horman@xxxxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.


[ Upstream commit d5d8760b78d0cfafe292f965f599988138b06a70 ]

Since 32b8a8e59c9c ("sit: add IPv4 over IPv4 support")
ipip6_err() may be called for packets whose IP protocol is
IPPROTO_IPIP as well as those whose IP protocol is IPPROTO_IPV6.

In the case of IPPROTO_IPIP packets the correct protocol value is not
passed to ipv4_update_pmtu() or ipv4_redirect().

This patch resolves this problem by using the IP protocol of the packet
rather than a hard-coded value. This appears to be consistent
with the usage of the protocol of a packet by icmp_socket_deliver()
the caller of ipip6_err().

I was able to exercise the redirect case by using a setup where an ICMP
redirect was received for the destination of the encapsulated packet.
However, it appears that although incorrect the protocol field is not used
in this case and thus no problem manifests. On inspection it does not
appear that a problem will manifest in the fragmentation needed/update pmtu
case either.

In short I believe this is a cosmetic fix. None the less, the use of
IPPROTO_IPV6 seems wrong and confusing.

Reviewed-by: Dinan Gunawardena <dinan.gunawardena@xxxxxxxxxxxxx>
Signed-off-by: Simon Horman <simon.horman@xxxxxxxxxxxxx>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
net/ipv6/sit.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index eb1fe0759752..a883776bcec8 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -529,13 +529,13 @@ static int ipip6_err(struct sk_buff *skb, u32 info)

if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
ipv4_update_pmtu(skb, dev_net(skb->dev), info,
- t->parms.link, 0, IPPROTO_IPV6, 0);
+ t->parms.link, 0, iph->protocol, 0);
err = 0;
goto out;
if (type == ICMP_REDIRECT) {
ipv4_redirect(skb, dev_net(skb->dev), t->parms.link, 0,
+ iph->protocol, 0);
err = 0;
goto out;