[PATCH 4.9 065/148] vti6: Dont report path MTU below IPV6_MIN_MTU.

Greg Kroah-Hartman
2017-12-12T12:57:58Z

From: Steffen Klassert <steffen.klassert@secunet.com>

[ Upstream commit e3dc847a5f85b43ee2bfc8eae407a7e383483228 ]

In vti6_xmit(), the check for IPV6_MIN_MTU before we
send a ICMPV6_PKT_TOOBIG message is missing. So we might
report a PMTU below 1280. Fix this by adding the required
check.

Fixes: ccd740cbc6e ("vti6: Add pmtu handling to vti6_xmit.")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/ip6_vti.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -485,11 +485,15 @@ vti6_xmit(struct sk_buff *skb, struct ne
if (!skb->ignore_df && skb->len > mtu) {
skb_dst(skb)->ops->update_pmtu(dst, NULL, skb, mtu);

- if (skb->protocol == htons(ETH_P_IPV6))
+ if (skb->protocol == htons(ETH_P_IPV6)) {
+ if (mtu < IPV6_MIN_MTU)
+ mtu = IPV6_MIN_MTU;
+
icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
- else
+ } else {
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
htonl(mtu));
+ }

return -EMSGSIZE;
}