netdev - Re: [PATCH] net: ipv6: don't generate link-local address in any addr_gen

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 9 Sep 2021 13:12:37 -0600
From:   David Ahern <dsahern@...il.com>
To:     Lorenzo Colitti <lorenzo@...gle.com>
Cc:     Rocco Yue <rocco.yue@...iatek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Linux NetDev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com,
        rocco.yue@...il.com, chao.song@...iatek.com,
        Kuohong Wang (王國鴻) 
        <kuohong.wang@...iatek.com>,
        Zhuoliang Zhang (张卓亮) 
        <zhuoliang.zhang@...iatek.com>
Subject: Re: [PATCH] net: ipv6: don't generate link-local address in any
 addr_gen_mode

On 9/9/21 12:20 AM, Lorenzo Colitti wrote:
>> I think another addr_gen_mode is better than a separate sysctl. It looks
>> like IN6_ADDR_GEN_MODE_STABLE_PRIVACY and IN6_ADDR_GEN_MODE_RANDOM are
>> the ones used for RAs, so add something like:
>>
>> IN6_ADDR_GEN_MODE_STABLE_PRIVACY_NO_LLA,
>> IN6_ADDR_GEN_MODE_RANDOM_NO_LLA,
> 
> I think the real requirement here (which wasn't clear in this thread)
> is that the network needs to control the interface ID (i.e., the
> bottom 64 bits) of the link-local address, but the device is free to
> use whatever interface IDs to form global addresses. See:
> https://www.etsi.org/deliver/etsi_ts/129000_129099/129061/15.03.00_60/ts_129061v150300p.pdf
> 
> How do you think that would best be implemented?

There is an established paradigm for configuring how an IPv6 address is
created or whether it is created at all - the IFLA_INET6_ADDR_GEN_MODE
attribute.

> 
> 1. The actual interface ID could be passed in using IFLA_INET6_TOKEN,
> but there is only one token, so that would cause all future addresses
> to use the token, disabling things like privacy addresses (bad).
> 2. We could add new IN6_ADDR_GEN_MODE_STABLE_PRIVACY_LL_TOKEN,
> IN6_ADDR_GEN_MODE_RANDOM_LL_TOKEN, etc., but we'd need to add one such
> mode for every new mode we add.
> 3. We could add a separate sysctl for the link-local address, but you
> said that per-device sysctls aren't free.

per-device sysctl's are one of primary causes of per netdev memory usage.

Besides that there is no reason to add complexity by having a link
attribute and a sysctl for this feature.

> 4. We could change the behaviour so that if the user configures a
> token and then sets IN6_ADDR_GEN_MODE_*, then we use the token only
> for the link-local address. But that would impact backwards
> compatibility.
> 
> Thoughts?

We can have up to 255 ADDR_GEN_MODEs (GEN_MODE is a u8). There is
established code for handling the attribute and changes to it. Let's
reuse it.