Subject: Re: [PATCHv2 bluetooth-next 07/10] ipv6: introduce neighbour discovery ops

From: Stefan Schmidt <[email-masked]>
Date: Tue, 3 May 2016 20:17:35 +0200

Hello.

On 02/05/16 21:36, Hannes Frederic Sowa wrote:
> On 20.04.2016 10:19, Alexander Aring wrote:
>> This patch introduces neighbour discovery ops callback structure. The
>> structure contains at first receive and transmit handling for NS/NA and
>> userspace option field functionality.
>>
>> These callback offers 6lowpan different handling, such as 802.15.4 short
>> address handling or RFC6775 (Neighbor Discovery Optimization for IPv6 over
>> 6LoWPANs).
>>
>> Cc: David S. Miller<davem-fT/PcQaiUtIeIZ0/[email-masked]>
>> Cc: Alexey Kuznetsov<kuznet-v/[email-masked]>
>> Cc: James Morris<jmorris-gx6/[email-masked]>
>> Cc: Hideaki YOSHIFUJI<[email-masked]>
>> Cc: Patrick McHardy<[email-masked]>
>> Signed-off-by: Alexander Aring<[email-masked]>
>> ---
>>   include/linux/netdevice.h |  3 ++
>>   include/net/ndisc.h       | 96 +++++++++++++++++++++++++++++++++++++++++++----
>>   net/ipv6/addrconf.c       |  1 +
>>   net/ipv6/ndisc.c          | 71 ++++++++++++++++++++++++-----------
>>   net/ipv6/route.c          |  2 +-
>>   5 files changed, 144 insertions(+), 29 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 0052c42..bc60033 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -1677,6 +1677,9 @@ struct net_device {
>>   #ifdef CONFIG_NET_L3_MASTER_DEV
>>   	const struct l3mdev_ops	*l3mdev_ops;
>>   #endif
>> +#if IS_ENABLED(CONFIG_IPV6)
>> +	const struct ndisc_ops *ndisc_ops;
>> +#endif
>>   
>>   	const struct header_ops *header_ops;
>>   
>> diff --git a/include/net/ndisc.h b/include/net/ndisc.h
>> index aac868e..14ed016 100644
>> --- a/include/net/ndisc.h
>> +++ b/include/net/ndisc.h
>> @@ -110,7 +110,8 @@ struct ndisc_options {
>>   
>>   #define NDISC_OPT_SPACE(len) (((len)+2+7)&~7)
>>   
>> -struct ndisc_options *ndisc_parse_options(u8 *opt, int opt_len,
>> +struct ndisc_options *ndisc_parse_options(const struct net_device *dev,
>> +					  u8 *opt, int opt_len,
>>   					  struct ndisc_options *ndopts);
>>   
>>   /*
>> @@ -173,6 +174,93 @@ static inline struct neighbour *__ipv6_neigh_lookup(struct net_device *dev, cons
>>   	return n;
>>   }
>>   
>> +static inline int __ip6_ndisc_is_useropt(struct nd_opt_hdr *opt)
>> +{
>> +	return opt->nd_opt_type == ND_OPT_RDNSS ||
>> +		opt->nd_opt_type == ND_OPT_DNSSL;
>> +}
>> +
>> +#if IS_ENABLED(CONFIG_IPV6)
>> +struct ndisc_ops {
>> +	int	(*is_useropt)(struct nd_opt_hdr *opt);
>> +	void	(*send_na)(struct net_device *dev,
>> +			   const struct in6_addr *daddr,
>> +			   const struct in6_addr *solicited_addr,
>> +			   bool router, bool solicited,
>> +			   bool override, bool inc_opt);
>> +	void	(*recv_na)(struct sk_buff *skb);
>> +	void	(*send_ns)(struct net_device *dev,
>> +			   const struct in6_addr *solicit,
>> +			   const struct in6_addr *daddr,
>> +			   const struct in6_addr *saddr);
>> +	void	(*recv_ns)(struct sk_buff *skb);
>> +};
>> +
>> +static inline int ndisc_is_useropt(const struct net_device *dev,
>> +				   struct nd_opt_hdr *opt)
>> +{
>> +	if (likely(dev->ndisc_ops->is_useropt))
>> +		return dev->ndisc_ops->is_useropt(opt);
>> +	else
>> +		return 0;
>> +}
>> +
>> +static inline void ndisc_send_na(struct net_device *dev,
>> +				 const struct in6_addr *daddr,
>> +				 const struct in6_addr *solicited_addr,
>> +				 bool router, bool solicited, bool override,
>> +				 bool inc_opt)
>> +{
>> +	if (likely(dev->ndisc_ops->send_na))
>> +		dev->ndisc_ops->send_na(dev, daddr, solicited_addr, router,
>> +					solicited, override, inc_opt);
>> +}
>> +
>> +static inline void ndisc_recv_na(struct sk_buff *skb)
>> +{
>> +	if (likely(skb->dev->ndisc_ops->recv_na))
>> +		skb->dev->ndisc_ops->recv_na(skb);
>> +}
>> +
>> +static inline void ndisc_send_ns(struct net_device *dev,
>> +				 const struct in6_addr *solicit,
>> +				 const struct in6_addr *daddr,
>> +				 const struct in6_addr *saddr)
>> +{
>> +	if (likely(dev->ndisc_ops->send_ns))
>> +		dev->ndisc_ops->send_ns(dev, solicit, daddr, saddr);
>> +}
>> +
>> +static inline void ndisc_recv_ns(struct sk_buff *skb)
>> +{
>> +	if (likely(skb->dev->ndisc_ops->recv_ns))
>> +		skb->dev->ndisc_ops->recv_ns(skb);
>> +}
>> +#else
>> +static inline int ndisc_is_useropt(const struct net_device *dev,
>> +				   struct nd_opt_hdr *opt)
>> +{
>> +	return 0;
>> +}
>> +
>> +static inline void ndisc_send_na(struct net_device *dev,
>> +				 const struct in6_addr *daddr,
>> +				 const struct in6_addr *solicited_addr,
>> +				 bool router, bool solicited, bool override,
>> +				 bool inc_opt) { }
>> +
>> +static inline void ndisc_recv_na(struct sk_buff *skb) { }
>> +
>> +static inline void ndisc_send_ns(struct net_device *dev,
>> +				 const struct in6_addr *solicit,
>> +				 const struct in6_addr *daddr,
>> +				 const struct in6_addr *saddr) { }
>> +
>> +static inline void ndisc_recv_ns(struct sk_buff *skb) { }
>> +#endif
> Do those empty functions actually make sense? I wonder a bit because
> 6lowpan strictly depends on ipv6 and they should never be called without
> IPv6, no?

Agreed. 6LoWAPN is only an adaptation layer so we know that IPv6 must be 
enabled here. I would also argue for removing this ifdef and the empty 
functions.

regards
Stefan Schmidt