net: Initialize entire flowi struct

The entire flowi struct needs to be initialized by afinfo->decode_session,
because flow_hash_code operates over the entire struct and may otherwise
return different hash values for what is intended to be the same key.

Signed-off-by: David Ward <david.ward@ll.mit.edu>
---
 net/ipv4/xfrm4_policy.c |    2 +-
 net/ipv6/xfrm6_policy.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

From: Julian Anastasov <ja@ssi.bg>
Date: Wed, 31 Aug 2011 23:51:32 +0300 (EEST)

> 	Such change will cause problems for callers that
> use flowi4 in stack. Examples:
> 
> ip_route_me_harder
> icmp_route_lookup

Right.
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Hello,

On Wed, 31 Aug 2011, David Ward wrote:

> The entire flowi struct needs to be initialized by afinfo->decode_session,
> because flow_hash_code operates over the entire struct and may otherwise
> return different hash values for what is intended to be the same key.

	Such change will cause problems for callers that
use flowi4 in stack. Examples:

ip_route_me_harder
icmp_route_lookup

	Not sure if adding size as parameter to flow_hash_code
is better approach. May be flow_cache_lookup needs to
determine size from family that can be used for flow_hash_code,
flow_key_compare and the memcpy(&fle->key, key, sizeof(*key))
after fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC). The
question is how to get size by family.

> Signed-off-by: David Ward <david.ward@ll.mit.edu>
> ---
>  net/ipv4/xfrm4_policy.c |    2 +-
>  net/ipv6/xfrm6_policy.c |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
> index fc5368a..afce24d 100644
> --- a/net/ipv4/xfrm4_policy.c
> +++ b/net/ipv4/xfrm4_policy.c
> @@ -114,7 +114,7 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
>  	u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
>  	struct flowi4 *fl4 = &fl->u.ip4;
>  
> -	memset(fl4, 0, sizeof(struct flowi4));
> +	memset(fl, 0, sizeof(struct flowi));
>  	fl4->flowi4_mark = skb->mark;
>  
>  	if (!ip_is_fragment(iph)) {
> diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
> index d879f7e..9088d38 100644
> --- a/net/ipv6/xfrm6_policy.c
> +++ b/net/ipv6/xfrm6_policy.c
> @@ -129,7 +129,7 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
>  	const unsigned char *nh = skb_network_header(skb);
>  	u8 nexthdr = nh[IP6CB(skb)->nhoff];
>  
> -	memset(fl6, 0, sizeof(struct flowi6));
> +	memset(fl, 0, sizeof(struct flowi));
>  	fl6->flowi6_mark = skb->mark;
>  
>  	ipv6_addr_copy(&fl6->daddr, reverse ? &hdr->saddr : &hdr->daddr);
> -- 
> 1.7.4.1

Regards

--
Julian Anastasov <ja@ssi.bg>
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Hi Julian,

On 08/31/2011 04:51 PM, Julian Anastasov wrote:
> On Wed, 31 Aug 2011, David Ward wrote
>> The entire flowi struct needs to be initialized by afinfo->decode_session,
>> because flow_hash_code operates over the entire struct and may otherwise
>> return different hash values for what is intended to be the same key.
> 	Such change will cause problems for callers that
> use flowi4 in stack. Examples:
>
> ip_route_me_harder
> icmp_route_lookup

Thanks for pointing this out.

> 	Not sure if adding size as parameter to flow_hash_code
> is better approach. May be flow_cache_lookup needs to
> determine size from family that can be used for flow_hash_code,
> flow_key_compare and the memcpy(&fle->key, key, sizeof(*key))
> after fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC).

Makes sense to me.  However should we just replace flow_key_compare with 
memcmp then, since the assumptions about constant size and alignment 
will no longer apply?  Or should there be a separate flow_key_compare 
function for each family, and have all of the flowi* structures become 
__attribute__((__aligned__(BITS_PER_LONG/8))) ?

David

> The question is how to get size by family.
>
>> Signed-off-by: David Ward<david.ward@ll.mit.edu>
>> ---
>>   net/ipv4/xfrm4_policy.c |    2 +-
>>   net/ipv6/xfrm6_policy.c |    2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
>> index fc5368a..afce24d 100644
>> --- a/net/ipv4/xfrm4_policy.c
>> +++ b/net/ipv4/xfrm4_policy.c
>> @@ -114,7 +114,7 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
>>   	u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
>>   	struct flowi4 *fl4 =&fl->u.ip4;
>>
>> -	memset(fl4, 0, sizeof(struct flowi4));
>> +	memset(fl, 0, sizeof(struct flowi));
>>   	fl4->flowi4_mark = skb->mark;
>>
>>   	if (!ip_is_fragment(iph)) {
>> diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
>> index d879f7e..9088d38 100644
>> --- a/net/ipv6/xfrm6_policy.c
>> +++ b/net/ipv6/xfrm6_policy.c
>> @@ -129,7 +129,7 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
>>   	const unsigned char *nh = skb_network_header(skb);
>>   	u8 nexthdr = nh[IP6CB(skb)->nhoff];
>>
>> -	memset(fl6, 0, sizeof(struct flowi6));
>> +	memset(fl, 0, sizeof(struct flowi));
>>   	fl6->flowi6_mark = skb->mark;
>>
>>   	ipv6_addr_copy(&fl6->daddr, reverse ?&hdr->saddr :&hdr->daddr);
>> -- 
>> 1.7.4.1

Hello,

On Thu, 1 Sep 2011, Ward, David - 0663 - MITLL wrote:

> > 	Not sure if adding size as parameter to flow_hash_code
> > is better approach. May be flow_cache_lookup needs to
> > determine size from family that can be used for flow_hash_code,
> > flow_key_compare and the memcpy(&fle->key, key, sizeof(*key))
> > after fle = kmem_cache_alloc(flow_cachep, GFP_ATOMIC).
> 
> Makes sense to me.  However should we just replace flow_key_compare with
> memcmp then, since the assumptions about constant size and alignment will no
> longer apply?  Or should there be a separate flow_key_compare function for
> each family, and have all of the flowi* structures become
> __attribute__((__aligned__(BITS_PER_LONG/8))) ?

	I don't know this code well but I guess memcmp is
not preferred. IMHO, as the callers provide per-family
structures and we do not want to change that, these
structures must be aligned to long type as required by
flow_compare_t and jhash2 (at least u32) usage. The second
option is to use memcmp and jhash instead of jhash2 to
avoid such alignment but I guess other developers will
oppose it. More opinions are needed here.

Regards

--
Julian Anastasov <ja@ssi.bg>
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These fixes to the flow cache are needed with the conversion to AF-specific
flowi structs. They are written so as to avoid introducing AF-specific code
into net/core/flow.c.

Note that __xfrm_policy_check (in net/xfrm/xfrm_policy.c) still allocates a
struct flowi on the stack and passes it to flow_cache_lookup. My understanding
is that since this is on the stack, this will not be aligned, and therefore it
will cause problems with flow_hash_code and flow_key_compare. Is that correct?

Signed-off-by: David Ward <david.ward@ll.mit.edu>

David Ward (2):
  net: Align AF-specific flowi structs to long
  net: Handle different key sizes between address families in flow
    cache

 include/net/flow.h |   25 ++++++++++++++++++++++---
 net/core/flow.c    |   28 ++++++++++++++++------------
 2 files changed, 38 insertions(+), 15 deletions(-)

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