netdev - Re: [PATCH net-next v4 1/5] tcp: add dropreasons definitions and prepare for cookie check

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Message-ID: <CAL+tcoCs2u9eR5WXGsnCmsORWCXsNgTXq4q1uRupBqJ8s7NuGA@mail.gmail.com>
Date: Wed, 14 Feb 2024 01:16:27 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	dsahern@...nel.org, kuniyu@...zon.com, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v4 1/5] tcp: add dropreasons definitions and
 prepare for cookie check

On Tue, Feb 13, 2024 at 11:24 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Feb 13, 2024 at 2:42 PM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Only add five drop reasons to detect the condition of skb dropped
> > in cookie check for later use.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > --
> > v2
> > Link: https://lore.kernel.org/netdev/20240212172302.3f95e454@kernel.org/
> > 1. fix misspelled name in kdoc as Jakub said
> > ---
> >  include/net/dropreason-core.h | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
> > index 6d3a20163260..065caba42b0b 100644
> > --- a/include/net/dropreason-core.h
> > +++ b/include/net/dropreason-core.h
> > @@ -6,6 +6,7 @@
> >  #define DEFINE_DROP_REASON(FN, FNe)    \
> >         FN(NOT_SPECIFIED)               \
> >         FN(NO_SOCKET)                   \
> > +       FN(NO_REQSK_ALLOC)              \
> >         FN(PKT_TOO_SMALL)               \
> >         FN(TCP_CSUM)                    \
> >         FN(SOCKET_FILTER)               \
> > @@ -43,10 +44,12 @@
> >         FN(TCP_FASTOPEN)                \
> >         FN(TCP_OLD_ACK)                 \
> >         FN(TCP_TOO_OLD_ACK)             \
> > +       FN(COOKIE_NOCHILD)              \
> >         FN(TCP_ACK_UNSENT_DATA)         \
> >         FN(TCP_OFO_QUEUE_PRUNE)         \
> >         FN(TCP_OFO_DROP)                \
> >         FN(IP_OUTNOROUTES)              \
> > +       FN(IP_ROUTEOUTPUTKEY)           \
> >         FN(BPF_CGROUP_EGRESS)           \
> >         FN(IPV6DISABLED)                \
> >         FN(NEIGH_CREATEFAIL)            \
> > @@ -54,6 +57,7 @@
> >         FN(NEIGH_QUEUEFULL)             \
> >         FN(NEIGH_DEAD)                  \
> >         FN(TC_EGRESS)                   \
> > +       FN(SECURITY_HOOK)               \
> >         FN(QDISC_DROP)                  \
> >         FN(CPU_BACKLOG)                 \
> >         FN(XDP)                         \
> > @@ -71,6 +75,7 @@
> >         FN(TAP_TXFILTER)                \
> >         FN(ICMP_CSUM)                   \
> >         FN(INVALID_PROTO)               \
> > +       FN(INVALID_DST)                 \
>
> We already have  SKB_DROP_REASON_IP_OUTNOROUTES ?

Oh right, I will reuse it.

>
> >         FN(IP_INADDRERRORS)             \
> >         FN(IP_INNOROUTES)               \
> >         FN(PKT_TOO_BIG)                 \
> > @@ -107,6 +112,11 @@ enum skb_drop_reason {
> >         SKB_DROP_REASON_NOT_SPECIFIED,
> >         /** @SKB_DROP_REASON_NO_SOCKET: socket not found */
> >         SKB_DROP_REASON_NO_SOCKET,
> > +       /**
> > +        * @SKB_DROP_REASON_NO_REQSK_ALLOC: request socket allocation failed
> > +        * probably because of no available memory for now
> > +        */
>
> We have SKB_DROP_REASON_NOMEM, I do not think we need to be very precise.
> REQSK are implementation details.

You're right about this.

>
> > +       SKB_DROP_REASON_NO_REQSK_ALLOC,
> >         /** @SKB_DROP_REASON_PKT_TOO_SMALL: packet size is too small */
> >         SKB_DROP_REASON_PKT_TOO_SMALL,
> >         /** @SKB_DROP_REASON_TCP_CSUM: TCP checksum error */
> > @@ -243,6 +253,11 @@ enum skb_drop_reason {
> >         SKB_DROP_REASON_TCP_OLD_ACK,
> >         /** @SKB_DROP_REASON_TCP_TOO_OLD_ACK: TCP ACK is too old */
> >         SKB_DROP_REASON_TCP_TOO_OLD_ACK,
> > +       /**
> > +        * @SKB_DROP_REASON_COOKIE_NOCHILD: no child socket in cookie mode
> > +        * reason could be the failure of child socket allocation
>
> This makes no sense to me. There are many reasons for this.

Let me think about a proper new name.

>
> Either the reason is deterministic, or just reuse a generic and
> existing drop_reason that can be augmented later.

I learned that.

Thanks,
Jason

>
> You are adding weak or duplicate drop_reasons, we already have them.