Subject: Re: [PATCH net-next 2/3] ipv6: use newly introduced __ipv6_addr_needs_scope_id and ipv6_iface_scope_id

From: YOSHIFUJI Hideaki <[email-masked]>
Date: Thu, 14 Feb 2013 01:47:47 +0900

Brian Haley wrote:
> On 02/12/2013 07:13 PM, Hannes Frederic Sowa wrote:
>>> --- a/net/ipv6/af_inet6.c
>>> +++ b/net/ipv6/af_inet6.c
>>> @@ -323,7 +323,7 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
>>>  			struct net_device *dev = NULL;
>>>  
>>>  			rcu_read_lock();
>>> -			if (addr_type & IPV6_ADDR_LINKLOCAL) {
>>> +			if (__ipv6_addr_needs_scope_id(addr_type)) {
>>>  				if (addr_len >= sizeof(struct sockaddr_in6) &&
>>>  				    addr->sin6_scope_id) {
>>>  					/* Override any existing binding, if another one
>>
>> By trying to setup the multicast interface scoped routes by default I
>> just found a bug in this patch essentially breaking ipv6 multicast. I
>> overlooked that ipv6_addr_type strips off the scopes, thus my check if
>> a multicast address needs a scope_id always returns true. I'll check
>> if I can convert the ipv6_addr_type calls to __ipv6_addr_type and will
>> reroll the patch.  Sorry, my tests were too focused on interface/local
>> multicast. :(
> 
> I'd always thought of adding helper inlines like these in net/ipv6.h:
> 
> static inline bool ipv6_addr_linklocal(const struct in6_addr *a)
> {
>         return ((a->s6_addr32[0] & htonl(0xFFC00000)) == htonl(0xFE800000));
> }
> 
> static inline bool ipv6_addr_mc_linklocal(const struct in6_addr *a)
> {
>         return (((a->s6_addr32[0] & htonl(0xFF000000)) == htonl(0xFF000000)) &&
>                 ((a->s6_addr32[1] & 0x0F) == IPV6_ADDR_SCOPE_LINKLOCAL));
> }
> 
> Maybe something like that would help here?

If you have several address checks around, please use ipv6_addr_type()
(or __ipv6_addr_type()).  Above "direct" checks should be used only for
single-shot test.  But well, I have to agree that ipv6_addr_type and
friends is becoming complex.  In mid-term, I would like to take look
at it.  I might think of having addr_type for src/dst in skb->cb
after all.

--yoshfuji