Re: [PATCH v6 net-next] net: drop_monitor: support drop reason

[Menglong Dong <menglong8.dong@gmail.com>]

On Sun, Feb 6, 2022 at 7:26 PM Ido Schimmel <idosch@idosch.org> wrote:
>
> On Sat, Feb 05, 2022 at 04:17:38PM +0800, menglong8.dong@gmail.com wrote:
> > diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
> > index 7b288a121a41..1180f1a28599 100644
> > --- a/net/core/drop_monitor.c
> > +++ b/net/core/drop_monitor.c
> > @@ -48,6 +48,16 @@
> >  static int trace_state = TRACE_OFF;
> >  static bool monitor_hw;
> >
> > +#undef EM
> > +#undef EMe
> > +
> > +#define EM(a, b)     [a] = #b,
> > +#define EMe(a, b)    [a] = #b
> > +
> > +static const char *drop_reasons[SKB_DROP_REASON_MAX + 1] = {
> > +     TRACE_SKB_DROP_REASON
> > +};
> > +
> >  /* net_dm_mutex
> >   *
> >   * An overall lock guarding every operation coming from userspace.
> > @@ -126,6 +136,7 @@ struct net_dm_skb_cb {
> >               struct devlink_trap_metadata *hw_metadata;
> >               void *pc;
> >       };
> > +     enum skb_drop_reason reason;
> >  };
> >
> >  #define NET_DM_SKB_CB(__skb) ((struct net_dm_skb_cb *)&((__skb)->cb[0]))
> > @@ -498,6 +509,7 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
> >  {
> >       ktime_t tstamp = ktime_get_real();
> >       struct per_cpu_dm_data *data;
> > +     struct net_dm_skb_cb *cb;
> >       struct sk_buff *nskb;
> >       unsigned long flags;
> >
> > @@ -508,7 +520,9 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore,
> >       if (!nskb)
> >               return;
> >
> > -     NET_DM_SKB_CB(nskb)->pc = location;
> > +     cb = NET_DM_SKB_CB(nskb);
> > +     cb->reason = reason;
> > +     cb->pc = location;
> >       /* Override the timestamp because we care about the time when the
> >        * packet was dropped.
> >        */
> > @@ -606,8 +620,9 @@ static int net_dm_packet_report_in_port_put(struct sk_buff *msg, int ifindex,
> >  static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
> >                                    size_t payload_len)
> >  {
> > -     u64 pc = (u64)(uintptr_t) NET_DM_SKB_CB(skb)->pc;
> > +     struct net_dm_skb_cb *cb = NET_DM_SKB_CB(skb);
> >       char buf[NET_DM_MAX_SYMBOL_LEN];
> > +     unsigned int reason;
> >       struct nlattr *attr;
> >       void *hdr;
> >       int rc;
> > @@ -620,10 +635,16 @@ static int net_dm_packet_report_fill(struct sk_buff *msg, struct sk_buff *skb,
> >       if (nla_put_u16(msg, NET_DM_ATTR_ORIGIN, NET_DM_ORIGIN_SW))
> >               goto nla_put_failure;
> >
> > -     if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, pc, NET_DM_ATTR_PAD))
> > +     if (nla_put_u64_64bit(msg, NET_DM_ATTR_PC, (u64)(uintptr_t)cb->pc,
> > +                           NET_DM_ATTR_PAD))
> > +             goto nla_put_failure;
> > +
> > +     reason = (unsigned int)cb->reason;
> > +     if (reason < SKB_DROP_REASON_MAX &&
> > +         nla_put_string(msg, NET_DM_ATTR_REASON, drop_reasons[reason]))
>
> You need to make sure 'msg' has enough room for this attribute. Account
> for it in net_dm_packet_report_size()
>

Ok, I see what you mean now, thanks!

> >               goto nla_put_failure;
> >
> > -     snprintf(buf, sizeof(buf), "%pS", NET_DM_SKB_CB(skb)->pc);
> > +     snprintf(buf, sizeof(buf), "%pS", cb->pc);
> >       if (nla_put_string(msg, NET_DM_ATTR_SYMBOL, buf))
> >               goto nla_put_failure;
> >
> > --
> > 2.27.0
> >