[PATCH] ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

[PATCH] ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

[Changli Gao]

6c79bf0f2440fd250c8fce8d9b82fcf03d4e8350 subtracts PPPOE_SES_HLEN from mtu at
the front of ip_fragment(). So the later subtraction should be removed. The
MTU of 802.1q is also 1500, so MTU should not be changed.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
 net/ipv4/ip_output.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 6652bd9..04b6989 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -446,7 +446,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	int ptr;
 	struct net_device *dev;
 	struct sk_buff *skb2;
-	unsigned int mtu, hlen, left, len, ll_rs, pad;
+	unsigned int mtu, hlen, left, len, ll_rs;
 	int offset;
 	__be16 not_last_frag;
 	struct rtable *rt = skb_rtable(skb);
@@ -585,9 +585,7 @@ slow_path:
 	/* for bridged IP traffic encapsulated inside f.e. a vlan header,
 	 * we need to make room for the encapsulating header
 	 */
-	pad = nf_bridge_pad(skb);
-	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, pad);
-	mtu -= pad;
+	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
 
 	/*
 	 *	Fragment the datagram.

Re: [PATCH] ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

[Patrick McHardy]

On 01.08.2010 01:25, Changli Gao wrote:
> 6c79bf0f2440fd250c8fce8d9b82fcf03d4e8350 subtracts PPPOE_SES_HLEN from mtu at
> the front of ip_fragment(). So the later subtraction should be removed. The
> MTU of 802.1q is also 1500, so MTU should not be changed.

Bart, please review, thanks.

> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> ----
>  net/ipv4/ip_output.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 6652bd9..04b6989 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -446,7 +446,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
>  	int ptr;
>  	struct net_device *dev;
>  	struct sk_buff *skb2;
> -	unsigned int mtu, hlen, left, len, ll_rs, pad;
> +	unsigned int mtu, hlen, left, len, ll_rs;
>  	int offset;
>  	__be16 not_last_frag;
>  	struct rtable *rt = skb_rtable(skb);
> @@ -585,9 +585,7 @@ slow_path:
>  	/* for bridged IP traffic encapsulated inside f.e. a vlan header,
>  	 * we need to make room for the encapsulating header
>  	 */
> -	pad = nf_bridge_pad(skb);
> -	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, pad);
> -	mtu -= pad;
> +	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
>  
>  	/*
>  	 *	Fragment the datagram.
> 

Re: [PATCH] ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

[Bart De Schuymer]

Patrick McHardy schreef:
> On 01.08.2010 01:25, Changli Gao wrote:
>   
>> 6c79bf0f2440fd250c8fce8d9b82fcf03d4e8350 subtracts PPPOE_SES_HLEN from mtu at
>> the front of ip_fragment(). So the later subtraction should be removed. The
>> MTU of 802.1q is also 1500, so MTU should not be changed.
>>     
>
> Bart, please review, thanks.
>
>   
The patch looks correct. The commit Changli refers to fixed the case 
where fragments are already available but broke the slow_path. The MTU 
for 802.1Q is indeed also 1500...

cheers,
Bart

Signed-off-by: Bart De Schuymer <bdschuym@pandora.bo>
>> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
>> ----
>>  net/ipv4/ip_output.c |    6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
>> index 6652bd9..04b6989 100644
>> --- a/net/ipv4/ip_output.c
>> +++ b/net/ipv4/ip_output.c
>> @@ -446,7 +446,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
>>  	int ptr;
>>  	struct net_device *dev;
>>  	struct sk_buff *skb2;
>> -	unsigned int mtu, hlen, left, len, ll_rs, pad;
>> +	unsigned int mtu, hlen, left, len, ll_rs;
>>  	int offset;
>>  	__be16 not_last_frag;
>>  	struct rtable *rt = skb_rtable(skb);
>> @@ -585,9 +585,7 @@ slow_path:
>>  	/* for bridged IP traffic encapsulated inside f.e. a vlan header,
>>  	 * we need to make room for the encapsulating header
>>  	 */
>> -	pad = nf_bridge_pad(skb);
>> -	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, pad);
>> -	mtu -= pad;
>> +	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
>>  
>>  	/*
>>  	 *	Fragment the datagram.
>>
>>     
>
>
>   


-- 
Bart De Schuymer
www.artinalgorithms.be

Re: [PATCH] ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

[David Miller]

From: Bart De Schuymer <bdschuym@pandora.be>
Date: Mon, 02 Aug 2010 21:20:16 +0200

> Patrick McHardy schreef:
>> On 01.08.2010 01:25, Changli Gao wrote:
>>   
>>> 6c79bf0f2440fd250c8fce8d9b82fcf03d4e8350 subtracts PPPOE_SES_HLEN from
>>> mtu at
>>> the front of ip_fragment(). So the later subtraction should be
>>> removed. The
>>> MTU of 802.1q is also 1500, so MTU should not be changed.
 ...
> Signed-off-by: Bart De Schuymer <bdschuym@pandora.bo>
>>> Signed-off-by: Changli Gao <xiaosuo@gmail.com>

Applied, thanks everyone.