netdev - Re: [PATCH net-next v2 08/14] net: ipv6: ip6mr: Extract a helper out of ip6mr

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Message-ID: <87sek32zl3.fsf@nvidia.com>
Date: Fri, 13 Jun 2025 21:40:38 +0200
From: Petr Machata <petrm@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Petr Machata <petrm@...dia.com>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, "David
 Ahern" <dsahern@...il.com>, <netdev@...r.kernel.org>, Simon Horman
	<horms@...nel.org>, Nikolay Aleksandrov <razor@...ckwall.org>, Ido Schimmel
	<idosch@...dia.com>, <mlxsw@...dia.com>
Subject: Re: [PATCH net-next v2 08/14] net: ipv6: ip6mr: Extract a helper
 out of ip6mr_forward2()


Jakub Kicinski <kuba@...nel.org> writes:

> On Thu, 12 Jun 2025 22:10:42 +0200 Petr Machata wrote:
>> -static int ip6mr_forward2(struct net *net, struct mr_table *mrt,
>> -			  struct sk_buff *skb, int vifi)
>> +static int ip6mr_prepare_xmit(struct net *net, struct mr_table *mrt,
>> +			      struct sk_buff *skb, int vifi)
>>  {
>>  	struct vif_device *vif = &mrt->vif_table[vifi];
>> -	struct net_device *indev = skb->dev;
>>  	struct net_device *vif_dev;
>>  	struct ipv6hdr *ipv6h;
>>  	struct dst_entry *dst;
>> @@ -2098,6 +2097,20 @@ static int ip6mr_forward2(struct net *net, struct mr_table *mrt,
>>  
>>  	ipv6h = ipv6_hdr(skb);
>>  	ipv6h->hop_limit--;
>> +	return 0;
>> +
>> +out_free:
>> +	kfree_skb(skb);
>> +	return -1;
>> +}
>
> ipmr_prepare_xmit() does not free the skb on error, and ip6mr_prepare_xmit() 
> does. The v6 version does lead to slightly cleaner code, but I wonder
> if its worth the asymmetry ?

Hmm, yeah, I think I had them symmetrical originally, but the
ipmr_forward_offloaded() call didn't make sense in ipmr_prepare_xmit(),
and pulled the cleanup up as it went out to the caller.

I'll do the same in IPv6, it makes sense to keep them similar.