From: Geliang Tang <geliangtang@gmail.com>
To: Paolo Abeni <pabeni@redhat.com>
Cc: mptcp@lists.linux.dev
Subject: Re: [PATCH mptcp-next 1/2] mptcp: optimize out option generation
Date: Mon, 26 Jul 2021 18:02:47 +0800 [thread overview]
Message-ID: <CA+WQbwuG7MTs9iv7K5eCwRpi1X9ioRoMMugCasHejmPnY5K-SA@mail.gmail.com> (raw)
In-Reply-To: <a816ed1d1be07abcd7fa55efe167141cd425426c.camel@redhat.com>
Paolo Abeni <pabeni@redhat.com> 于2021年7月26日周一 下午5:44写道：
>
> On Mon, 2021-07-26 at 11:21 +0800, Geliang Tang wrote:
> > Hi Paolo,
> >
> > Thanks for this patchset, and I have some small comments.
> >
> > Paolo Abeni <pabeni@redhat.com> 于2021年7月24日周六 上午1:06写道：
> > > Currently we have several protocol contraint on MPTCP option
> > > generation (e.g. MPC and MPJ subopt are mutually exclusive)
> > > and some additionall ones required by our implementation
> > > (e.g. almost all ADD_ADDR variant are mutually exclusive with
> > > everything else).
> > >
> > > We can leverage the above to optimize the out option generation:
> > > we check DSS/MPC/MPJ presencence in a mutually exclusive way,
> > > avoiding many unneeded conditionals in the common case.
> > >
> > > Additionally extend the existing constraint on ADD_ADDR opt on
> > > all subvariant, so that it become fully mutually exclusive with
> > > the above and we can skip another conditional statement the common
> > > case.
> > >
> > > This change is also need by the next patch.
> > >
> > > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > > --
> > > side node: we could probably optimize the conditionals in
> > > mptcp_established_options()
> > > ---
> > > net/mptcp/options.c | 225 ++++++++++++++++++++++---------------------
> > > net/mptcp/pm.c | 9 +-
> > > net/mptcp/protocol.h | 1 +
> > > 3 files changed, 122 insertions(+), 113 deletions(-)
> > >
> > > diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> > > index eafdb9408f3a..38f324667761 100644
> > > --- a/net/mptcp/options.c
> > > +++ b/net/mptcp/options.c
> > > @@ -592,6 +592,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
> > > dss_size = map_size;
> > > if (skb && snd_data_fin_enable)
> > > mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
> > > + opts->suboptions = OPTION_MPTCP_DSS;
> > > ret = true;
> > > }
> > >
> > > @@ -615,6 +616,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
> > > opts->ext_copy.ack64 = 0;
> > > }
> > > opts->ext_copy.use_ack = 1;
> > > + opts->suboptions = OPTION_MPTCP_DSS;
> > > WRITE_ONCE(msk->old_wspace, __mptcp_space((struct sock *)msk));
> > >
> > > /* Add kind/length/subtype/flag overhead if mapping is not populated */
> > > @@ -663,9 +665,9 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
> >
> > I think no need to modify the code in mptcp_established_options_add_addr.
> >
> > > struct mptcp_sock *msk = mptcp_sk(subflow->conn);
> > > bool drop_other_suboptions = false;
> > > unsigned int opt_size = *size;
> > > + unsigned int len;
> > > bool echo;
> > > bool port;
> > > - int len;
> >
> > I prefer to keep the type of len unchanged.
>
> OK.
>
> >
> > > if (!mptcp_pm_should_add_signal(msk) ||
> > > !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, opts,
> > > @@ -687,11 +689,12 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
> > > *size -= opt_size;
> > > }
> > > opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
> > > - if (!echo) {
> > > + if (!echo)
> > > opts->ahmac = add_addr_generate_hmac(msk->local_key,
> > > msk->remote_key,
> > > &opts->addr);
> > > - }
> > > + else
> > > + opts->ahmac = 0;
> >
> > opts->ahmac had been set to zero in mptcp_get_options, no need to clear it
> > again.
>
> This is for the output path, mptcp_get_options() is not invoked. 'ops'
Sorry, my fault.
> has been cleared by the TCP caller. Sice a few fields are aliased, and
> the add_addr is added after the DSS, the latter could have already
> modified the underlaying memory.
>
> Without this assignment we will end-up appending the hmac even for
> add_addr 'echo', and a bunch of tests will fail.
>
> Perhaps is better adding some comments explaining why such set
> operation is needed...
Yes, that's helpful.
> >
> > > pr_debug("addr_id=%d, addr_port=%d, ahmac=%llu, echo=%d",
> > > opts->addr.id, ntohs(opts->addr.port), opts->ahmac, echo);
> > >
> > > @@ -735,7 +738,12 @@ static bool mptcp_established_options_mp_prio(struct sock *sk,
> > > {
> > > struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
> > >
> > > - if (!subflow->send_mp_prio)
> > > + /* can't send MP_PRIO with MPC, as they share the same option space:
> > > + * 'backup'. Also it makes no sense at all
> > > + */
> > > + if (!subflow->send_mp_prio ||
> > > + ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
> > > + OPTION_MPTCP_MPC_ACK) & opts->suboptions))
> > > return false;
> > >
> > > /* account for the trailing 'nop' option */
> > > @@ -1198,7 +1206,73 @@ static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
> > > void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
> > > struct mptcp_out_options *opts)
> > > {
> > > - if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
> > > + /* RST is mutually exclusive with everything else */
> > > + if (unlikely(OPTION_MPTCP_RST & opts->suboptions)) {
> > > + *ptr++ = mptcp_option(MPTCPOPT_RST,
> > > + TCPOLEN_MPTCP_RST,
> > > + opts->reset_transient,
> > > + opts->reset_reason);
> > > + return;
> > > + }
> > > +
> > > + /* DSS, MPC, MPJ and ADD_ADDR are mutually exclusive, see
> > > + * mptcp_established_options*()
> > > + */
> > > + if (likely(OPTION_MPTCP_DSS & opts->suboptions)) {
> > > + struct mptcp_ext *mpext = &opts->ext_copy;
> > > + u8 len = TCPOLEN_MPTCP_DSS_BASE;
> > > + u8 flags = 0;
> > > +
> > > + if (mpext->use_ack) {
> > > + flags = MPTCP_DSS_HAS_ACK;
> > > + if (mpext->ack64) {
> > > + len += TCPOLEN_MPTCP_DSS_ACK64;
> > > + flags |= MPTCP_DSS_ACK64;
> > > + } else {
> > > + len += TCPOLEN_MPTCP_DSS_ACK32;
> > > + }
> > > + }
> > > +
> > > + if (mpext->use_map) {
> > > + len += TCPOLEN_MPTCP_DSS_MAP64;
> > > +
> > > + /* Use only 64-bit mapping flags for now, add
> > > + * support for optional 32-bit mappings later.
> > > + */
> > > + flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
> > > + if (mpext->data_fin)
> > > + flags |= MPTCP_DSS_DATA_FIN;
> > > +
> > > + if (opts->csum_reqd)
> > > + len += TCPOLEN_MPTCP_DSS_CHECKSUM;
> > > + }
> > > +
> > > + *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
> > > +
> > > + if (mpext->use_ack) {
> > > + if (mpext->ack64) {
> > > + put_unaligned_be64(mpext->data_ack, ptr);
> > > + ptr += 2;
> > > + } else {
> > > + put_unaligned_be32(mpext->data_ack32, ptr);
> > > + ptr += 1;
> > > + }
> > > + }
> > > +
> > > + if (mpext->use_map) {
> > > + put_unaligned_be64(mpext->data_seq, ptr);
> > > + ptr += 2;
> > > + put_unaligned_be32(mpext->subflow_seq, ptr);
> > > + ptr += 1;
> > > + if (opts->csum_reqd) {
> > > + put_unaligned_be32(mpext->data_len << 16 |
> > > + mptcp_make_csum(mpext), ptr);
> > > + } else {
> > > + put_unaligned_be32(mpext->data_len << 16 |
> > > + TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
> > > + }
> > > + }
> > > + } else if ((OPTION_MPTCP_MPC_SYN | OPTION_MPTCP_MPC_SYNACK |
> > > OPTION_MPTCP_MPC_ACK) & opts->suboptions) {
> > > u8 len, flag = MPTCP_CAP_HMAC_SHA256;
> > >
> > > @@ -1246,10 +1320,31 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
> > > TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
> > > }
> > > ptr += 1;
> > > - }
> > >
> > > -mp_capable_done:
> > > - if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
> > > + /* MPC is additionally mutually exclusive with MP_PRIO */
> > > + goto mp_capable_done;
> > > + } else if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
> > > + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > + TCPOLEN_MPTCP_MPJ_SYN,
> > > + opts->backup, opts->join_id);
> > > + put_unaligned_be32(opts->token, ptr);
> > > + ptr += 1;
> > > + put_unaligned_be32(opts->nonce, ptr);
> > > + ptr += 1;
> > > + } else if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
> > > + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > + TCPOLEN_MPTCP_MPJ_SYNACK,
> > > + opts->backup, opts->join_id);
> > > + put_unaligned_be64(opts->thmac, ptr);
> > > + ptr += 2;
> > > + put_unaligned_be32(opts->nonce, ptr);
> > > + ptr += 1;
> > > + } else if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
> > > + *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > + TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
> > > + memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
> > > + ptr += 5;
> > > + } else if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
> > > struct mptcp_addr_info *addr = &opts->addr;
> > > u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
> > > u8 echo = MPTCP_ADDR_ECHO;
> > > @@ -1308,6 +1403,19 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
> > > }
> > > }
> > >
> > > + if (OPTION_MPTCP_PRIO & opts->suboptions) {
> > > + const struct sock *ssk = (const struct sock *)tp;
> > > + struct mptcp_subflow_context *subflow;
> > > +
> > > + subflow = mptcp_subflow_ctx(ssk);
> > > + subflow->send_mp_prio = 0;
> > > +
> > > + *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
> > > + TCPOLEN_MPTCP_PRIO,
> > > + opts->backup, TCPOPT_NOP);
> > > + }
> > > +
> > > +mp_capable_done:
> > > if (OPTION_MPTCP_RM_ADDR & opts->suboptions) {
> > > u8 i = 1;
> > >
> > > @@ -1328,107 +1436,6 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
> > > }
> > > }
> > >
> > > - if (OPTION_MPTCP_PRIO & opts->suboptions) {
> > > - const struct sock *ssk = (const struct sock *)tp;
> > > - struct mptcp_subflow_context *subflow;
> > > -
> > > - subflow = mptcp_subflow_ctx(ssk);
> > > - subflow->send_mp_prio = 0;
> > > -
> > > - *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
> > > - TCPOLEN_MPTCP_PRIO,
> > > - opts->backup, TCPOPT_NOP);
> > > - }
> > > -
> > > - if (OPTION_MPTCP_MPJ_SYN & opts->suboptions) {
> > > - *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > - TCPOLEN_MPTCP_MPJ_SYN,
> > > - opts->backup, opts->join_id);
> > > - put_unaligned_be32(opts->token, ptr);
> > > - ptr += 1;
> > > - put_unaligned_be32(opts->nonce, ptr);
> > > - ptr += 1;
> > > - }
> > > -
> > > - if (OPTION_MPTCP_MPJ_SYNACK & opts->suboptions) {
> > > - *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > - TCPOLEN_MPTCP_MPJ_SYNACK,
> > > - opts->backup, opts->join_id);
> > > - put_unaligned_be64(opts->thmac, ptr);
> > > - ptr += 2;
> > > - put_unaligned_be32(opts->nonce, ptr);
> > > - ptr += 1;
> > > - }
> > > -
> > > - if (OPTION_MPTCP_MPJ_ACK & opts->suboptions) {
> > > - *ptr++ = mptcp_option(MPTCPOPT_MP_JOIN,
> > > - TCPOLEN_MPTCP_MPJ_ACK, 0, 0);
> > > - memcpy(ptr, opts->hmac, MPTCPOPT_HMAC_LEN);
> > > - ptr += 5;
> > > - }
> > > -
> > > - if (OPTION_MPTCP_RST & opts->suboptions)
> > > - *ptr++ = mptcp_option(MPTCPOPT_RST,
> > > - TCPOLEN_MPTCP_RST,
> > > - opts->reset_transient,
> > > - opts->reset_reason);
> > > -
> > > - if (opts->ext_copy.use_ack || opts->ext_copy.use_map) {
> > > - struct mptcp_ext *mpext = &opts->ext_copy;
> > > - u8 len = TCPOLEN_MPTCP_DSS_BASE;
> > > - u8 flags = 0;
> > > -
> > > - if (mpext->use_ack) {
> > > - flags = MPTCP_DSS_HAS_ACK;
> > > - if (mpext->ack64) {
> > > - len += TCPOLEN_MPTCP_DSS_ACK64;
> > > - flags |= MPTCP_DSS_ACK64;
> > > - } else {
> > > - len += TCPOLEN_MPTCP_DSS_ACK32;
> > > - }
> > > - }
> > > -
> > > - if (mpext->use_map) {
> > > - len += TCPOLEN_MPTCP_DSS_MAP64;
> > > -
> > > - /* Use only 64-bit mapping flags for now, add
> > > - * support for optional 32-bit mappings later.
> > > - */
> > > - flags |= MPTCP_DSS_HAS_MAP | MPTCP_DSS_DSN64;
> > > - if (mpext->data_fin)
> > > - flags |= MPTCP_DSS_DATA_FIN;
> > > -
> > > - if (opts->csum_reqd)
> > > - len += TCPOLEN_MPTCP_DSS_CHECKSUM;
> > > - }
> > > -
> > > - *ptr++ = mptcp_option(MPTCPOPT_DSS, len, 0, flags);
> > > -
> > > - if (mpext->use_ack) {
> > > - if (mpext->ack64) {
> > > - put_unaligned_be64(mpext->data_ack, ptr);
> > > - ptr += 2;
> > > - } else {
> > > - put_unaligned_be32(mpext->data_ack32, ptr);
> > > - ptr += 1;
> > > - }
> > > - }
> > > -
> > > - if (mpext->use_map) {
> > > - put_unaligned_be64(mpext->data_seq, ptr);
> > > - ptr += 2;
> > > - put_unaligned_be32(mpext->subflow_seq, ptr);
> > > - ptr += 1;
> > > - if (opts->csum_reqd) {
> > > - put_unaligned_be32(mpext->data_len << 16 |
> > > - mptcp_make_csum(mpext), ptr);
> > > - } else {
> > > - put_unaligned_be32(mpext->data_len << 16 |
> > > - TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
> > > - }
> > > - }
> > > - }
> > > -
> > > if (tp)
> > > mptcp_set_rwin(tp);
> > > }
> > > diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
> > > index 4d1828fd2482..baf2d6e524bd 100644
> > > --- a/net/mptcp/pm.c
> > > +++ b/net/mptcp/pm.c
> > > @@ -266,10 +266,11 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
> > > if (!mptcp_pm_should_add_signal(msk))
> > > goto out_unlock;
> > >
> > > - if (((msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_ECHO)) ||
> > > - ((msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL)) &&
> > > - (msk->pm.local.family == AF_INET6 || msk->pm.local.port))) &&
> > > - skb && skb_is_tcp_pure_ack(skb)) {
> > > + /* always drop every other options for pure ack ADD_ADDR; this is
> > > + * plain dup-ack from TCP perspective. The other MPTCP-relevant info,
> > > + * if any, will be carried by the other pure ack
> > > + */
> > > + if (skb && skb_is_tcp_pure_ack(skb)) {
> > > remaining += opt_size;
> > > *drop_other_suboptions = true;
> > > }
> >
> > This part in pm.c should be squashed to the patch "mptcp: move
> > drop_other_suboptions check under pm lock".
> >
> > WDYT?
>
> I was wondering if that chunk would deserve a separate patch.
Sure, a separate patch is fine.
Thanks,
-Geliang
>
> Squashing the change in another patch would still mix multiple intens
> in a single change, but the modifications are indeed related. Overall
> agreed ;)
>
> /P
>
>
>
next prev parent reply other threads:[~2021-07-26 10:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 17:06 [PATCH mptcp-next 0/2] mptcp: minor out optimization Paolo Abeni
2021-07-23 17:06 ` [PATCH mptcp-next 1/2] mptcp: optimize out option generation Paolo Abeni
2021-07-26 3:21 ` Geliang Tang
2021-07-26 9:44 ` Paolo Abeni
2021-07-26 10:02 ` Geliang Tang [this message]
2021-07-26 10:06 ` Paolo Abeni
2021-07-23 17:06 ` [PATCH mptcp-next 2/2] mptcp: shrink mptcp_out_options struct Paolo Abeni
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