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Date:   Thu, 4 Aug 2022 10:03:58 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, kernel-team@...com,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v2 bpf-next 15/15] selftests/bpf: bpf_setsockopt tests

On Wed, Aug 3, 2022 at 5:04 PM Martin KaFai Lau <kafai@...com> wrote:
>
> On Wed, Aug 03, 2022 at 04:30:54PM -0700, sdf@...gle.com wrote:
> > > +struct sock_common {
> > > +   unsigned short  skc_family;
> > > +   unsigned long   skc_flags;
> > > +   unsigned char   skc_reuse:4;
> > > +   unsigned char   skc_reuseport:1;
> > > +   unsigned char   skc_ipv6only:1;
> > > +   unsigned char   skc_net_refcnt:1;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct sock {
> > > +   struct sock_common      __sk_common;
> > > +   __u16                   sk_type;
> > > +   __u16                   sk_protocol;
> > > +   int                     sk_rcvlowat;
> > > +   __u32                   sk_mark;
> > > +   unsigned long           sk_max_pacing_rate;
> > > +   unsigned int            keepalive_time;
> > > +   unsigned int            keepalive_intvl;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct tcp_options_received {
> > > +   __u16 user_mss;
> > > +} __attribute__((preserve_access_index));
> >
> > I'm assuming you're not using vmlinux here because it doesn't bring
> > it most of the defines? Should we add missing stuff to bpf_tracing_net.h
> > instead?
> Ah, actually my first attempt was to use vmlinux.h and had
> all defines ready for addition to bpf_tracing_net.h.
>
> However, I hit an issue in reading bitfield.  It is why the
> bitfield in the tcp_sock below is sandwiched between __u32.
> I think it is likely LLVM and/or CO-RE related. Yonghong is
> helping to investigate it.
>
> In the mean time, I define those mini struct here.
> Once the bitfield issue is resolved, we can go back to
> use vmlinux.h.

Oh, interesting :-)

> > > +struct ipv6_pinfo {
> > > +   __u16                   recverr:1,
> > > +                           sndflow:1,
> > > +                           repflow:1,
> > > +                           pmtudisc:3,
> > > +                           padding:1,
> > > +                           srcprefs:3,
> > > +                           dontfrag:1,
> > > +                           autoflowlabel:1,
> > > +                           autoflowlabel_set:1,
> > > +                           mc_all:1,
> > > +                           recverr_rfc4884:1,
> > > +                           rtalert_isolate:1;
> > > +}  __attribute__((preserve_access_index));
> > > +
> > > +struct inet_sock {
> > > +   /* sk and pinet6 has to be the first two members of inet_sock */
> > > +   struct sock             sk;
> > > +   struct ipv6_pinfo       *pinet6;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct inet_connection_sock {
> > > +   __u32                     icsk_user_timeout;
> > > +   __u8                      icsk_syn_retries;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct tcp_sock {
> > > +   struct inet_connection_sock     inet_conn;
> > > +   struct tcp_options_received rx_opt;
> > > +   __u8    save_syn:2,
> > > +           syn_data:1,
> > > +           syn_fastopen:1,
> > > +           syn_fastopen_exp:1,
> > > +           syn_fastopen_ch:1,
> > > +           syn_data_acked:1,
> > > +           is_cwnd_limited:1;
> > > +   __u32   window_clamp;
> > > +   __u8    nonagle     : 4,
> > > +           thin_lto    : 1,
> > > +           recvmsg_inq : 1,
> > > +           repair      : 1,
> > > +           frto        : 1;
> > > +   __u32   notsent_lowat;
> > > +   __u8    keepalive_probes;
> > > +   unsigned int            keepalive_time;
> > > +   unsigned int            keepalive_intvl;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct socket {
> > > +   struct sock *sk;
> > > +} __attribute__((preserve_access_index));
> > > +
> > > +struct loop_ctx {
> > > +   void *ctx;
> > > +   struct sock *sk;
> > > +};
> > > +
> > > +static int __bpf_getsockopt(void *ctx, struct sock *sk,
> > > +                       int level, int opt, int *optval,
> > > +                       int optlen)
> > > +{
> > > +   if (level == SOL_SOCKET) {
> > > +           switch (opt) {
> > > +           case SO_REUSEADDR:
> > > +                   *optval = !!(sk->__sk_common.skc_reuse);
> > > +                   break;
> > > +           case SO_KEEPALIVE:
> > > +                   *optval = !!(sk->__sk_common.skc_flags & (1UL << 3));
> > > +                   break;
> > > +           case SO_RCVLOWAT:
> > > +                   *optval = sk->sk_rcvlowat;
> > > +                   break;
> >
> > What's the idea with the options above? Why not allow them in
> > bpf_getsockopt instead?
> I am planning to refactor the bpf_getsockopt also,
> so trying to avoid adding more dup code at this point
> while they can directly be read from sk through PTR_TO_BTF_ID.
>
> btw, since we are on bpf_getsockopt(), do you still see a usage on
> bpf_getsockopt() for those 'integer-value' optnames that can be
> easily read from the sk pointer ?

Writing is still done via bpf_setsockopt, so having the same interface
to read the settings seems useful?




> > > +           case SO_MARK:
> > > +                   *optval = sk->sk_mark;
> > > +                   break;
> >
> > SO_MARK should be handled by bpf_getsockopt ?
> Good point, will remove SO_MARK case.
>
> Thanks for the review!

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