Re: [PATCH bpf-next v2] bpf: Fix bpf_get/setsockopt to tos not take effect when TCP over IPv4 via INET6 API

[Eric Dumazet]

On Fri, Aug 23, 2024 at 8:49 PM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote:
>
> On 8/23/24 6:35 AM, Eric Dumazet wrote:
> > On Fri, Aug 23, 2024 at 10:53 AM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
> >>
> >> From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> >>
> >> when TCP over IPv4 via INET6 API, bpf_get/setsockopt with ipv4 will
> >> fail, because sk->sk_family is AF_INET6. With ipv6 will success, not
> >> take effect, because inet_csk(sk)->icsk_af_ops is ipv6_mapped and
> >> use ip_queue_xmit, inet_sk(sk)->tos.
> >>
> >> So bpf_get/setsockopt needs add the judgment of this case. Just check
> >> "inet_csk(sk)->icsk_af_ops == &ipv6_mapped".
> >>
> >> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> >> | Closes: https://lore.kernel.org/oe-kbuild-all/202408152034.lw9Ilsj6-lkp@xxxxxxxxx/
> >> Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> >> ---
> >> Changelog:
> >> v1->v2: Addressed comments from kernel test robot
> >> - Fix compilation error
> >> Details in here:
> >> https://lore.kernel.org/bpf/202408152058.YXAnhLgZ-lkp@xxxxxxxxx/T/
> >>
> >>   include/net/tcp.h   | 2 ++
> >>   net/core/filter.c   | 6 +++++-
> >>   net/ipv6/tcp_ipv6.c | 6 ++++++
> >>   3 files changed, 13 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/include/net/tcp.h b/include/net/tcp.h
> >> index 2aac11e7e1cc..ea673f88c900 100644
> >> --- a/include/net/tcp.h
> >> +++ b/include/net/tcp.h
> >> @@ -493,6 +493,8 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
> >>                                              struct tcp_options_received *tcp_opt,
> >>                                              int mss, u32 tsoff);
> >>
> >> +bool is_tcp_sock_ipv6_mapped(struct sock *sk);
> >> +
> >>   #if IS_ENABLED(CONFIG_BPF)
> >>   struct bpf_tcp_req_attrs {
> >>          u32 rcv_tsval;
> >> diff --git a/net/core/filter.c b/net/core/filter.c
> >> index ecf2ddf633bf..02a825e35c4d 100644
> >> --- a/net/core/filter.c
> >> +++ b/net/core/filter.c
> >> @@ -5399,7 +5399,11 @@ static int sol_ip_sockopt(struct sock *sk, int optname,
> >>                            char *optval, int *optlen,
> >>                            bool getopt)
> >>   {
> >> -       if (sk->sk_family != AF_INET)
> >> +       if (sk->sk_family != AF_INET
> >> +#if IS_BUILTIN(CONFIG_IPV6)
> >> +           && !is_tcp_sock_ipv6_mapped(sk)
> >> +#endif
> >> +           )
> >>                  return -EINVAL;
> >
> > This does not look right to me.
> >
> > I would remove the test completely.
> >
> > SOL_IP socket options are available on AF_INET6 sockets just fine.
>
> Good point on the SOL_IP options.
>
> The sk could be neither AF_INET nor AF_INET6. e.g. the bpf_get/setsockopt
> calling from the bpf_lsm's socket_post_create). so the AF_INET test is still needed.
>

OK, then I suggest using sk_is_inet() helper.

> Adding "&& sk->sk_family != AF_INET6" should do. From ipv6_setsockopt, I think
> it also needs to consider the "sk->sk_type != SOCK_RAW".
>
> Please add a test in the next re-spin.
>
> pw-bot: cr