netdev - Re: [PATCH net 1/2] ipv6: add ipv6_dev

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Message-ID: <9aec8657-ac6e-f10a-2b6e-a544a0aa9ab5@gmail.com>
Date:   Wed, 5 Aug 2020 10:31:06 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ying Xue <ying.xue@...driver.com>, Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, Jon Maloy <jon.maloy@...csson.com>,
        tipc-discussion@...ts.sourceforge.net,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH net 1/2] ipv6: add ipv6_dev_find()

On 8/5/20 5:03 AM, Ying Xue wrote:
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index 840bfdb..857d6f9 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -1983,6 +1983,45 @@ int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev)
>>  }
>>  EXPORT_SYMBOL(ipv6_chk_prefix);
>>  
>> +/**
>> + * ipv6_dev_find - find the first device with a given source address.
>> + * @net: the net namespace
>> + * @addr: the source address
>> + *
>> + * The caller should be protected by RCU, or RTNL.
>> + */
>> +struct net_device *ipv6_dev_find(struct net *net, const struct in6_addr *addr)
>> +{
>> +	unsigned int hash = inet6_addr_hash(net, addr);
>> +	struct inet6_ifaddr *ifp, *result = NULL;
>> +	struct net_device *dev = NULL;
>> +
>> +	rcu_read_lock();
>> +	hlist_for_each_entry_rcu(ifp, &inet6_addr_lst[hash], addr_lst) {
>> +		if (net_eq(dev_net(ifp->idev->dev), net) &&
>> +		    ipv6_addr_equal(&ifp->addr, addr)) {
>> +			result = ifp;
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (!result) {
>> +		struct rt6_info *rt;
>> +
>> +		rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);

why is this needed? you have already walked the interfaces in the
namespace and not found the address. Doing a route lookup is beyond the
stated scope of this function.

>> +		if (rt) {
>> +			dev = rt->dst.dev;
>> +			ip6_rt_put(rt);
>> +		}
>> +	} else {
>> +		dev = result->idev->dev;
>> +	}
>> +	rcu_read_unlock();
>> +
>> +	return dev;
>> +}
>> +EXPORT_SYMBOL(ipv6_dev_find);
>> +
>>  struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net, const struct in6_addr *addr,
>>  				     struct net_device *dev, int strict)
>>  {
>>