Re: [Regression w/ patch] Restore network resistance to weird ICMP messages

[Vicente JimÃnez]

Corrected patch attached.
Thanks for the advices.
I was unaware of those style policies.

On Thu, Nov 10, 2016 at 2:22 AM, David Miller <davem@xxxxxxxxxxxxx> wrote:
> From: Vicente JimÃnez <googuy@xxxxxxxxx>
> Date: Mon, 7 Nov 2016 12:11:59 +0100
>
>> From bfc9a00e6b78d8eb60e46dacd7d761669d29a573 Mon Sep 17 00:00:00 2001
>> From: Vicente Jimenez Aguilar <googuy@xxxxxxxxx>
>> Date: Mon, 31 Oct 2016 13:10:29 +0100
>> Subject: [PATCH] ipv4: icmp: Fix pMTU handling for rarest case
>>
>> Restore network resistance to weird 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@xxxxxxxxx>
>> ---
>>  net/ipv4/icmp.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
>> index 38abe70..c0af1d2 100644
>> --- a/net/ipv4/icmp.c
>> +++ b/net/ipv4/icmp.c
>> @@ -776,6 +776,7 @@ static bool icmp_unreach(struct sk_buff *skb)
>>       struct icmphdr *icmph;
>>       struct net *net;
>>       u32 info = 0;
>> +     unsigned short old_mtu;
>>
>>       net = dev_net(skb_dst(skb)->dev);
>>
>
> Order local variable declarations from longest to shortest line
> please.
>
>> +                             if ( info >= old_mtu )
>
> There should be no space after the '(' and before the ')' in this
> conditional.



-- 
saludos
vicente
From 88ac49fa287e2e0d3d3bc805dea1fec301aad1df Mon Sep 17 00:00:00 2001
From: Vicente Jimenez Aguilar <googuy@xxxxxxxxx>
Date: Mon, 31 Oct 2016 13:10:29 +0100
Subject: [PATCH] ipv4: icmp: Fix pMTU handling for rarest case

Restore network resistance to weird 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@xxxxxxxxx>
---
 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:
-- 
2.7.3