Re: [PATCH net-next 3/3] vxlan: allow multiple VXLANs with same VNI for IPv6 link-local addresses

From: Matthias Schiffer
Date: Wed Mar 15 2017 - 10:30:37 EST


On 03/14/2017 04:28 PM, Jiri Benc wrote:
> On Fri, 10 Mar 2017 23:39:44 +0100, Matthias Schiffer wrote:
>> @@ -233,17 +234,30 @@ static struct vxlan_dev *vxlan_vs_find_vni(struct vxlan_sock *vs, __be32 vni)
>> vni = 0;
>>
>> hlist_for_each_entry_rcu(vxlan, vni_head(vs, vni), hlist) {
>> - if (vxlan->default_dst.remote_vni == vni)
>> - return vxlan;
>> + if (vxlan->default_dst.remote_vni != vni)
>> + continue;
>> +
>> + if (IS_ENABLED(CONFIG_IPV6)) {
>> + const struct vxlan_config *cfg = &vxlan->cfg;
>> +
>> + if (cfg->remote_ifindex != 0 &&
>> + cfg->remote_ifindex != ifindex &&
>> + cfg->saddr.sa.sa_family == AF_INET6 &&
>> + (ipv6_addr_type(&cfg->saddr.sin6.sin6_addr) &
>> + IPV6_ADDR_LINKLOCAL))
>
> Calculating this (especially ipv6_addr_type) on every received packet
> looks unnecessarily expensive. Just store the fact the the local
> address is link-local in a flag during config. And compare the flag
> first before considering remote_ifindex.
>
> This is especially important for lwtunnels which can have anything in
> the saddr and remote_ifindex, yet those fields are ignored and the
> vni 0 entry has to be returned. It also means that the link-local flag
> must not be set for lwtunnels.
>
>> +#if IS_ENABLED(CONFIG_IPV6)
>> + if (conf->remote_ifindex != tmp->cfg.remote_ifindex &&
>> + conf->saddr.sa.sa_family == AF_INET6 &&
>> + tmp->cfg.saddr.sa.sa_family == AF_INET6 &&
>> + (ipv6_addr_type(&conf->saddr.sin6.sin6_addr) &
>> + IPV6_ADDR_LINKLOCAL) &&
>> + (ipv6_addr_type(&tmp->cfg.saddr.sin6.sin6_addr) &
>> + IPV6_ADDR_LINKLOCAL))
>> + continue;
>> +#endif
>
> In patch 1, you're checking for either source and destination address
> being link-local, while here you're consider only those that have both
> addresses link-local.
>
> Wouldn't it be better to plainly reject configuration that has one
> address link-local but not the other one?

While ensuring that the destination address is link-local iff the source
address is would also be an option, it didn't seem too useful as the
destination address will be a multicast address anyways in "normal" VXLAN
configurations. If we really want to check this, I guess the valid
combinations are:

source link-local - destination link-local UC
source link-local - destination link-local MC
source global/... - destination global/... UC
source global/... - destination any MC

Does this make sense?


>
> Jiri

Thanks for your comments, I'll send a v2 soon.

Matthias




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