lkml.org 
[lkml]   [2018]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] netfilter: NFT_SOCKET don't use NF_SOCKET_IPV6 without NF_TABLES_IPV6
    On Tue, Jul 10, 2018 at 11:10:40AM +0200, Arnd Bergmann wrote:
    > On Tue, Jul 10, 2018 at 10:05 AM, Máté Eckl <ecklm94@gmail.com> wrote:
    > > On Tue, Jul 10, 2018 at 10:02:27AM +0200, Máté Eckl wrote:
    > >> On Mon, Jul 09, 2018 at 11:35:09PM +0200, Arnd Bergmann wrote:
    > >> > It is now possible to build the nft_socket module as built-in when
    > >> > NF_TABLES_IPV6 is disabled, and have NF_SOCKET_IPV6=m set manually.
    > >> >
    > >> > In this case, the NF_SOCKET_IPV6 functionality will be useless according
    > >> > to the explanation in commit 35bf1ccecaaa ("netfilter: Kconfig: Change
    > >> > IPv6 select dependencies"), but on top of that it also causes a link
    > >> > error:
    > >> >
    > >> > net/netfilter/nft_socket.o: In function `nft_socket_eval':
    > >> > nft_socket.c:(.text+0x162): undefined reference to `nf_sk_lookup_slow_v6'
    > >> >
    > >> > This changes the compile-time check so we don't attempt to use
    > >> > the NF_SOCKET_IPV6 code when it cannot be used, and make it all
    > >> > compile again. That may lead to unexpected behavior when a user
    > >> > enables NF_SOCKET_IPV6 but cannot use it, but seems to be the
    > >> > logical conclusion of the 35bf1ccecaaa change.
    > >> >
    > >> > Fixes: 35bf1ccecaaa ("netfilter: Kconfig: Change IPv6 select dependencies")
    > >> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    > >>
    > >> I think this should be fixed in the Kconfig rather than inside the module(s).
    >
    > Should we revert your patch then, or do you have a better idea?
    >
    > >> I did some investigation and it turns out that you missed a circumstance. This
    > >> link error occures only if NFT_SOCKET=y && NF_SOCKET_IPV6=m && NF_TABLES_IPV6=y
    > >> (cannot be m here if NFT_SOCKET is y).
    >
    > No, if NF_TABLES_IPV6=y the problem cannot happen, since NFT_SOCKET then
    > selects NF_SOCKET_IPV6=y as well. Before your patch, it would always select
    > NF_SOCKET_IPV6 when it could, so it worked in all configurations.

    Sorry I wanted to write NF_TABLES_IPV6=n...
    So: NFT_SOCKET=y && NF_SOCKET_IPV6=m && NF_TABLES_IPV6=n causes linkage error.
    NFT_SOCKET=m && NF_SOCKET_IPV6=m && NF_TABLES_IPV6=n compiles fine.

    > >> And probably the same with
    > >> iptables-related modules. Probably this possibility should be eliminated.
    > >
    > > NF_TPROXY_IPV6 might be in the same situation.
    >
    > I tried coming up with a combination that is broken for NF_TPROXY_IPV6=m
    > but could not. From what I can see with
    >
    > config NETFILTER_XT_TARGET_TPROXY
    > tristate '"TPROXY" target transparent proxying support'
    > depends on IP6_NF_IPTABLES || IP6_NF_IPTABLES=n
    > select NF_TPROXY_IPV6 if IP6_NF_IPTABLES
    >
    > and
    >
    > #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
    >
    > inside of net/netfilter/xt_TPROXY.c, there is no way we can end up with
    > xt_TPROXY calling into the nf_tproxy_ipv6 loadable module from
    > a built-in context. This is the same approach I used in my patch,
    > just with IP6_NF_IPTABLES instead of NF_SOCKET_IPV6, in both
    > the Kconfig dependency and the module.

    Right, I see your point. I have an alternative solution which seems more robust
    to me, but I might be overthinking this situation.

    So
    Accepted-by: Máté Eckl <ecklm94@gmail.com>

    > Arnd

    \
     
     \ /
      Last update: 2018-07-10 11:52    [W:2.239 / U:0.392 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site