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Date: Fri, 11 Nov 2016 21:20:18 +0100
From: Vicente Jimenez Aguilar <googuy@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Vicente Jimenez Aguilar <googuy@...il.com>
Subject: [PATCH] icmp: Restore resistence to abnormal messages
Restore network resistance to abnormal ICMP fragmentation needed messages
with next hop MTU equal to (or exceeding) dropped packet size
Fixes: 46517008e116 ("ipv4: Kill ip_rt_frag_needed().")
Signed-off-by: Vicente Jimenez Aguilar <googuy@...il.com>
---
net/ipv4/icmp.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 38abe70..4c90d76 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -773,6 +773,7 @@ static bool icmp_tag_validation(int proto)
static bool icmp_unreach(struct sk_buff *skb)
{
const struct iphdr *iph;
+ unsigned short old_mtu;
struct icmphdr *icmph;
struct net *net;
u32 info = 0;
@@ -819,6 +820,12 @@ static bool icmp_unreach(struct sk_buff *skb)
/* fall through */
case 0:
info = ntohs(icmph->un.frag.mtu);
+ /* Handle weird case where next hop MTU is
+ * equal to or exceeding dropped packet size
+ */
+ old_mtu = ntohs(iph->tot_len);
+ if (info >= old_mtu)
+ info = old_mtu - 2;
}
break;
case ICMP_SR_FAILED:
--
2.9.3
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