Subject: Re: [PATCH net-next] ip: introduce ip_is_fragment helper inline function

From: Paul Gortmaker <[email-masked]>
Date: Fri, 17 Jun 2011 14:24:14 -0400

On 11-06-17 02:19 PM, Ben Hutchings wrote:
> On Fri, 2011-06-17 at 14:08 -0400, Paul Gortmaker wrote:
>> There are enough instances of this:
>>
>>     iph->frag_off & htons(IP_MF | IP_OFFSET)
>>
>> that a helper function is probably warranted.
> [...]
>> --- a/drivers/net/s2io.c
>> +++ b/drivers/net/s2io.c
>> @@ -4111,7 +4111,7 @@ static netdev_tx_t s2io_xmit(struct sk_buff *skb, struct net_device *dev)
>>  			struct tcphdr *th;
>>  			ip = ip_hdr(skb);
>>  
>> -			if ((ip->frag_off & htons(IP_OFFSET|IP_MF)) == 0) {
>> +			if (ip_is_fragment(ip) == 0) {
>>  				th = (struct tcphdr *)(((unsigned char *)ip) +
>>  						       ip->ihl*4);
>>  
> 
> The condition should be written more clearly as !ip_is_fragment().

Agreed, and I actually had that but then "un-did" it since
I didn't want to force my choices of coding style down
into drivers.  Maybe I was just being overcautious.

> 
> [...]
>> diff --git a/include/net/ip.h b/include/net/ip.h
>> index e9ea7c7..114a152 100644
>> --- a/include/net/ip.h
>> +++ b/include/net/ip.h
>> @@ -250,6 +250,11 @@ int ip_decrease_ttl(struct iphdr *iph)
>>  	return --iph->ttl;
>>  }
>>  
>> +static inline int ip_is_fragment(const struct iphdr *iph)
>> +{
>> +	return iph->frag_off & htons(IP_MF | IP_OFFSET);
>> +}
>> +
>>  static inline
>>  int ip_dont_fragment(struct sock *sk, struct dst_entry *dst)
>>  {
> [..]
> 
> The return type should be bool.

I can make that change.  I'll sit on it for a bit in case anyone
else sees anything else needing a tweak.

Thanks Ben,
Paul.

> Ben.