From: Paolo Abeni <pabeni@redhat.com>
To: Geliang Tang <geliangtang@gmail.com>
Cc: mptcp@lists.linux.dev
Subject: Re: [MPTCP][PATCH v3 mptcp-next 1/8] mptcp: MP_FAIL suboption sending
Date: Wed, 14 Jul 2021 17:49:49 +0200 [thread overview]
Message-ID: <8166dbe9c65a722a342e455ef9a0088da16f4da7.camel@redhat.com> (raw)
In-Reply-To: <CA+WQbwt_76G1hVXmPUwbZXfraa=2KqBQAv1sYF17Bf=+V_mYSQ@mail.gmail.com>
On Wed, 2021-07-14 at 17:16 +0800, Geliang Tang wrote:
> Paolo Abeni <pabeni@redhat.com> 于2021年7月14日周三 下午4:45写道:
> > On Mon, 2021-06-28 at 12:28 +0800, Geliang Tang wrote:
> > > This patch added the MP_FAIL suboption sending support.
> > >
> > > Add a new flag named send_mp_fail in struct mptcp_subflow_context. If
> > > this flag is set, send out MP_FAIL suboption.
> > >
> > > Add a new member fail_seq in struct mptcp_out_options to save the data
> > > sequence number to put into the MP_FAIL suboption.
> > >
> > > Signed-off-by: Geliang Tang <geliangtang@gmail.com>
> > > ---
> > > include/net/mptcp.h | 1 +
> > > net/mptcp/options.c | 54 ++++++++++++++++++++++++++++++++++++++++++--
> > > net/mptcp/protocol.h | 4 ++++
> > > 3 files changed, 57 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/net/mptcp.h b/include/net/mptcp.h
> > > index cb580b06152f..f48d3b5a3fd4 100644
> > > --- a/include/net/mptcp.h
> > > +++ b/include/net/mptcp.h
> > > @@ -72,6 +72,7 @@ struct mptcp_out_options {
> > > u32 nonce;
> > > u64 thmac;
> > > u32 token;
> > > + u64 fail_seq;
> >
> > Since we can't have both a valid mapping and MP_FAIL in the same
> > packet, it would be better to avoid increasing the 'mptcp_out_options'
> > size, e.g. re-using some ext_copy field, or unioning with some other
> > field.
>
> The RFC says an MP_FAIL option could be included in a RST or on the
> subflow-level ACK. So I think we can't re-using the ext_copy field if it's
> on the subflow-level ACK.
>
> How about unioning this fail_seq field with ahmac field?
>
> > mptcp_out_options has grown quite a bit and we should really look into
> > shrinking it.
> >
> > > u8 hmac[20];
> > > struct mptcp_ext ext_copy;
> > > #endif
> > > diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> > > index b5850afea343..b78defe1aed9 100644
> > > --- a/net/mptcp/options.c
> > > +++ b/net/mptcp/options.c
> > > @@ -771,6 +771,28 @@ static noinline void mptcp_established_options_rst(struct sock *sk, struct sk_bu
> > > opts->reset_reason = subflow->reset_reason;
> > > }
> > >
> > > +static bool mptcp_established_options_mp_fail(struct sock *sk,
> > > + unsigned int *size,
> > > + unsigned int remaining,
> > > + struct mptcp_out_options *opts)
> > > +{
> > > + struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
> > > +
> > > + if (!subflow->send_mp_fail)
> > > + return false;
> > > +
> > > + if (remaining < TCPOLEN_MPTCP_FAIL)
> > > + return false;
> > > +
> > > + *size = TCPOLEN_MPTCP_FAIL;
> > > + opts->suboptions |= OPTION_MPTCP_FAIL;
> > > + opts->fail_seq = subflow->fail_seq;
> > > +
> > > + pr_debug("MP_FAIL fail_seq=%llu", opts->fail_seq);
> > > +
> > > + return true;
> > > +}
> > > +
> > > bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
> > > unsigned int *size, unsigned int remaining,
> > > struct mptcp_out_options *opts)
> > > @@ -787,15 +809,29 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
> > > return false;
> > >
> > > if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST)) {
> > > - mptcp_established_options_rst(sk, skb, size, remaining, opts);
> > > + if (mptcp_established_options_mp_fail(sk, &opt_size, remaining, opts)) {
> > > + *size += opt_size;
> > > + remaining -= opt_size;
> > > + }
> > > + mptcp_established_options_rst(sk, skb, &opt_size, remaining, opts);
> > > + *size += opt_size;
> > > + remaining -= opt_size;
> > > return true;
> > > }
> > >
> > > snd_data_fin = mptcp_data_fin_enabled(msk);
> > > if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
> > > ret = true;
> > > - else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
> > > + else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts)) {
> > > ret = true;
> > > + if (opts->ext_copy.use_ack) {
> >
> > Is the extra check on 'opts->ext_copy.use_ack' necessary? can we just
> > look for mp_fail?
> >
>
> I added this check since the RFC says an MP_FAIL option could be included
> on the subflow-level ACK:
>
> '''
> In this case, if a receiver identifies a checksum failure when there is
> only one path, it will send back an MP_FAIL option on the subflow-level
> ACK, referring to the data-level sequence number of the start of the
> segment on which the checksum error was detected.
> '''
>
> Do I understand right?
Not a big deal, but I read the above as follow:
the MP_FAIL is included into the next subflow packet/
subflow-level ACK really means TCP-level ACK, I think. Since the
subflow is established (at TCP level) each TCP packet will carry an
ack.
All in all the ' if (opts->ext_copy.use_ack) {' check looks unneeded to
me.
Cheers,
Paolo
prev parent reply other threads:[~2021-07-14 15:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 4:28 [MPTCP][PATCH v3 mptcp-next 0/8] MP_FAIL support Geliang Tang
2021-06-28 4:28 ` [MPTCP][PATCH v3 mptcp-next 1/8] mptcp: MP_FAIL suboption sending Geliang Tang
2021-06-28 4:28 ` [MPTCP][PATCH v3 mptcp-next 2/8] mptcp: MP_FAIL suboption receiving Geliang Tang
2021-06-28 4:28 ` [MPTCP][PATCH v3 mptcp-next 3/8] mptcp: send out MP_FAIL when data checksum fail Geliang Tang
2021-06-28 4:29 ` [MPTCP][PATCH v3 mptcp-next 4/8] mptcp: add the mibs for MP_FAIL Geliang Tang
2021-06-28 4:29 ` [MPTCP][PATCH v3 mptcp-next 5/8] selftests: mptcp: add MP_FAIL mibs check Geliang Tang
2021-06-28 4:29 ` [MPTCP][PATCH v3 mptcp-next 6/8] mptcp: infinite mapping sending Geliang Tang
2021-06-28 4:29 ` [MPTCP][PATCH v3 mptcp-next 7/8] mptcp: infinite mapping receiving Geliang Tang
2021-06-28 4:29 ` [MPTCP][PATCH v3 mptcp-next 8/8] mptcp: add a mib for the infinite mapping sending Geliang Tang
2021-07-07 23:49 ` [MPTCP][PATCH v3 mptcp-next 7/8] mptcp: infinite mapping receiving Mat Martineau
2021-07-07 23:44 ` [MPTCP][PATCH v3 mptcp-next 6/8] mptcp: infinite mapping sending Mat Martineau
2021-07-08 0:44 ` Mat Martineau
2021-07-07 23:20 ` [MPTCP][PATCH v3 mptcp-next 3/8] mptcp: send out MP_FAIL when data checksum fail Mat Martineau
2021-07-13 12:44 ` Geliang Tang
2021-07-13 20:35 ` Mat Martineau
2021-07-14 3:56 ` Geliang Tang
2021-07-14 17:48 ` Mat Martineau
2021-07-07 23:07 ` [MPTCP][PATCH v3 mptcp-next 1/8] mptcp: MP_FAIL suboption sending Mat Martineau
2021-07-14 8:45 ` Paolo Abeni
2021-07-14 9:16 ` Geliang Tang
2021-07-14 15:49 ` Paolo Abeni [this message]
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