Re: [MPTCP][PATCH mptcp-next] Squash to "mptcp: build ADD_ADDR/echo-ADD_ADDR option according pm.add_signal"

[Geliang Tang <geliangtang@gmail.com>]

Geliang Tang <geliangtang@gmail.com> 于2021年7月12日周一 下午4:44写道：
>
> Yonglong Li <liyonglong@chinatelecom.cn> 于2021年7月12日周一 下午4:07写道：
> >
> >
> >
> > On 2021/7/12 15:33, Geliang Tang wrote:
> > > Hi Yonglong,
> > >
> > > Yonglong Li <liyonglong@chinatelecom.cn> 于2021年7月12日周一 上午9:34写道：
> > >>
> > >>
> > >>
> > >> On 2021/7/11 23:15, Geliang Tang wrote:
> > >>> I think there're still some issues in v8:
> > >>>
> > >>> The remaining value is incorrect since "remaining += opt_size;" in the
> > >>> "drop other suboptions" checks has been called twice in
> > >>> mptcp_pm_add_addr_signal and mptcp_established_options_add_addr.
> > >>>
> > >> I think "remaining" in mptcp_pm_add_addr_signal does not touch "remaining" in
> > >> mptcp_established_options_add_addr.
> > >>
> > >>> opts->local and opts->remote in mptcp_pm_add_addr_signal need be
> > >>> populate after the length chech, not before the check.]
> > >>>
> > >>> The squash-to patch keeped the more orignal code unchanged, and just do
> > >>> the least, necessary modifications.
> > >>>
> > >> Agree opts->local and opts->remote should be asigned after the length check.
> > >> But if keep the length check out of mptcp_pm_add_addr_signal (out of pm lock )
> > >> as orignal code, there is a race that:
> > >>
> > >> ==> a add addr event (pm.addr_signal == MPTCP_ADD_ADDR_SIGNAL)
> > >> ==> call mptcp_pm_add_addr_signal
> > >> ==> a echo add addr event trigger (pm.addr_signal == MPTCP_ADD_ADDR_ECHO|MPTCP_ADD_ADDR_SIGNAL)
> > >> ==> at this time opts->remote is empty and the length is incorrect.
> > >>
> > >
> > > What will happen in v8 when this race occurs? How dose v8 deal with the
> > > race?
> > Hi Geliang, thinks for your patience.
> >
> > I think v8 doesn't have this issue:
> > ==> a add addr event (pm.addr_signal == MPTCP_ADD_ADDR_SIGNAL)
> > ==> call mptcp_pm_add_addr_signal, save pm.addr_signal to add_addr and save addr in opts under pm.lock
> > ==> a echo add addr event trigger (pm.addr_signal == MPTCP_ADD_ADDR_ECHO), but add_addr doesn't changed.
> > ==> use add_addr and opts to check length.
> > ==> next send ack process will deal with MPTCP_ADD_ADDR_ECHO event.
>
> Thanks for your explanation.
>
> I think this squash-to patch did the same thing:
>
> ==> an add addr event (pm.addr_signal == MPTCP_ADD_ADDR_SIGNAL)
> ==> call mptcp_pm_add_addr_signal, save echo bit of pm.addr_signal to
> 'echo' (echo = false), save the port number to 'port', and save addr
> in opts under pm.lock
> ==> an echo add addr event trigger (pm.addr_signal ==
> MPTCP_ADD_ADDR_ECHO), but 'echo' and 'port' don't changed.
> ==> use 'echo' to get the address family, use 'family', 'echo' and
> 'port' to check length.
> ==> next send ack process will deal with MPTCP_ADD_ADDR_ECHO event.
>
> Do you think so?

And one more thing. How do you test this "mptcp: fix conflicts when using
pm.add_signal in ADD_ADDR/echo and RM_ADDR process" series? Do you use our
mptcp_join.sh to test it, or you did some special tests? Does this race
scenario mentioned above easy to reproduce?

I just did the mptcp_join.sh tests for my squash-to patches, and everything
looks fine. If you have some special tests, could you please help me to test
these squash-to patches too? Hope it works in the race scenario.

Thanks.
-Geliang



>
> >
> > >
> > >> So I think the orignal code is incorrect. WDYT?
> > >>
> > >>> Drop the "drop other suboptions" check in mptcp_pm_add_addr_signal.
> > >>>
> > >>> Change arguments of mptcp_pm_add_addr_signal.
> > >>>
> > >>> Keep mptcp_add_addr_len unchanged.
> > >>>
> > >>> Signed-off-by: Geliang Tang <geliangtang@gmail.com>
> > >>> ---
> > >>>  net/mptcp/options.c  | 35 +++++++++++++++++------------------
> > >>>  net/mptcp/pm.c       | 23 +++++++++--------------
> > >>>  net/mptcp/protocol.h | 27 +++++++++------------------
> > >>>  3 files changed, 35 insertions(+), 50 deletions(-)
> > >>>
> > >>> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> > >>> index 5c0ad9b90866..93ad7b134f74 100644
> > >>> --- a/net/mptcp/options.c
> > >>> +++ b/net/mptcp/options.c
> > >>> @@ -663,16 +663,14 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
> > >>>       struct mptcp_sock *msk = mptcp_sk(subflow->conn);
> > >>>       bool drop_other_suboptions = false;
> > >>>       unsigned int opt_size = *size;
> > >>> -     u8 add_addr;
> > >>> +     bool echo;
> > >>> +     bool port;
> > >>> +     u8 family;
> > >>>       int len;
> > >>>
> > >>> -     if (!mptcp_pm_should_add_signal(msk) ||
> > >>> -         !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, opts, &add_addr))
> > >>> -             return false;
> > >>> -
> > >>> -     if (((add_addr & BIT(MPTCP_ADD_ADDR_ECHO)) ||
> > >>> -          ((add_addr & BIT(MPTCP_ADD_ADDR_SIGNAL)) &&
> > >>> -           (opts->local.family == AF_INET6 || opts->local.port))) &&
> > >>> +     if ((mptcp_pm_should_add_signal_echo(msk) ||
> > >>> +          (mptcp_pm_should_add_signal_addr(msk) &&
> > >>> +           (msk->pm.local.family == AF_INET6 || msk->pm.local.port))) &&
> > >>>           skb && skb_is_tcp_pure_ack(skb)) {
> > >>>               pr_debug("drop other suboptions");
> > >>>               opts->suboptions = 0;
> > >>> @@ -682,7 +680,12 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
> > >>>               drop_other_suboptions = true;
> > >>>       }
> > >>>
> > >>> -     len = mptcp_add_addr_len(opts, add_addr);
> > >>> +     if (!mptcp_pm_should_add_signal(msk) ||
> > >>> +         !mptcp_pm_add_addr_signal(msk, remaining, &opts->local, &opts->remote, &echo, &port))
> > >>> +             return false;
> > >>> +
> > >>> +     family = echo ? opts->remote.family : opts->local.family;
> > >>> +     len = mptcp_add_addr_len(family, echo, port);
> > >>>       if (remaining < len)
> > >>>               return false;
> > >>>
> > >>> @@ -690,15 +693,14 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff *
> > >>>       if (drop_other_suboptions)
> > >>>               *size -= opt_size;
> > >>>       opts->suboptions |= OPTION_MPTCP_ADD_ADDR;
> > >>> -     if (!(add_addr & BIT(MPTCP_ADD_ADDR_ECHO)) &&
> > >>> -         (add_addr & BIT(MPTCP_ADD_ADDR_SIGNAL))) {
> > >>> +     if (!echo) {
> > >>>               opts->ahmac = add_addr_generate_hmac(msk->local_key,
> > >>>                                                    msk->remote_key,
> > >>>                                                    &opts->local);
> > >>>       }
> > >>> -     pr_debug("addr_signal:%x, echo=%d, local_addr_id=%d, ahmac=%llu, local_port=%d, remote_addr_id=%d, remote_port=%d",
> > >>> -              add_addr, (opts->ahmac == 0), opts->local.id, opts->ahmac,
> > >>> -              ntohs(opts->local.port), opts->remote.id, ntohs(opts->remote.port));
> > >>> +     pr_debug("local_id=%d, local_port=%d, remote_id=%d, remote_port=%d, ahmac=%llu, echo=%d",
> > >>> +              opts->local.id, ntohs(opts->local.port), opts->remote.id,
> > >>> +              ntohs(opts->remote.port), opts->ahmac, echo);
> > >>>
> > >>>       return true;
> > >>>  }
> > >>> @@ -1253,13 +1255,10 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
> > >>>
> > >>>  mp_capable_done:
> > >>>       if (OPTION_MPTCP_ADD_ADDR & opts->suboptions) {
> > >>> -             struct mptcp_addr_info *addr = &opts->remote;
> > >>> +             struct mptcp_addr_info *addr = opts->ahmac ? &opts->local : &opts->remote;
> > >>>               u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
> > >>>               u8 echo = MPTCP_ADDR_ECHO;
> > >>>
> > >>> -             if (opts->ahmac)
> > >>> -                     addr = &opts->local;
> > >>> -
> > >>>  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
> > >>>               if (addr->family == AF_INET6)
> > >>>                       len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
> > >>> diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
> > >>> index 264f522af530..399b59cb7563 100644
> > >>> --- a/net/mptcp/pm.c
> > >>> +++ b/net/mptcp/pm.c
> > >>> @@ -253,12 +253,13 @@ void mptcp_pm_mp_prio_received(struct sock *sk, u8 bkup)
> > >>>
> > >>>  /* path manager helpers */
> > >>>
> > >>> -bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
> > >>> -                           unsigned int opt_size, unsigned int remaining,
> > >>> -                           struct mptcp_out_options *opts,  u8 *add_addr)
> > >>> +bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
> > >>> +                           struct mptcp_addr_info *saddr, struct mptcp_addr_info *daddr,
> > >>> +                           bool *echo, bool *port)
> > >>>  {
> > >>>       int ret = false;
> > >>>       u8 add_addr;
> > >>> +     u8 family;
> > >>>
> > >>>       spin_lock_bh(&msk->pm.lock);
> > >>>
> > >>> @@ -266,21 +267,15 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
> > >>>       if (!mptcp_pm_should_add_signal(msk))
> > >>>               goto out_unlock;
> > >>>
> > >>> -     opts->local = msk->pm.local;
> > >>> -     opts->remote = msk->pm.remote;
> > >>> -     *add_addr = msk->pm.addr_signal;
> > >>> +     *echo = mptcp_pm_should_add_signal_echo(msk);
> > >>> +     *port = !!(*echo ? msk->pm.remote.port : msk->pm.local.port);
> > >>>
> > >>> -     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)) {
> > >>> -             remaining += opt_size;
> > >>> -     }
> > >>> -
> > >>> -     if (remaining < mptcp_add_addr_len(opts, *add_addr))
> > >>> +     family = *echo ? msk->pm.remote.family : msk->pm.local.family;
> > >>> +     if (remaining < mptcp_add_addr_len(family, *echo, *port))
> > >>>               goto out_unlock;
> > >>>
> > >>>       *saddr = msk->pm.local;
> > >>> +     *daddr = msk->pm.remote;
> > >>>       add_addr = READ_ONCE(msk->pm.addr_signal);
> > >>>       if (mptcp_pm_should_add_signal_echo(msk))
> > >>>               add_addr &= ~BIT(MPTCP_ADD_ADDR_ECHO);
> > >>> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> > >>> index 937e0309e340..4b63cc6079fa 100644
> > >>> --- a/net/mptcp/protocol.h
> > >>> +++ b/net/mptcp/protocol.h
> > >>> @@ -766,25 +766,16 @@ static inline bool mptcp_pm_should_rm_signal(struct mptcp_sock *msk)
> > >>>       return READ_ONCE(msk->pm.addr_signal) & BIT(MPTCP_RM_ADDR_SIGNAL);
> > >>>  }
> > >>>
> > >>> -static inline unsigned int mptcp_add_addr_len(struct mptcp_out_options *opts,
> > >>> -                                           u8 add_addr)
> > >>> +static inline unsigned int mptcp_add_addr_len(int family, bool echo, bool port)
> > >>>  {
> > >>> -     struct mptcp_addr_info *addr = &opts->remote;
> > >>> -     u8 len = 0;
> > >>> +     u8 len = TCPOLEN_MPTCP_ADD_ADDR_BASE;
> > >>>
> > >>> -     if (!(add_addr & BIT(MPTCP_ADD_ADDR_ECHO)) &&
> > >>> -         (add_addr & BIT(MPTCP_ADD_ADDR_SIGNAL))) {
> > >>> -             addr = &opts->local;
> > >>> +     if (family == AF_INET6)
> > >>> +             len = TCPOLEN_MPTCP_ADD_ADDR6_BASE;
> > >>> +     if (!echo)
> > >>>               len += MPTCPOPT_THMAC_LEN;
> > >>> -     }
> > >>> -
> > >>> -     if (addr->family == AF_INET6)
> > >>> -             len += TCPOLEN_MPTCP_ADD_ADDR6_BASE;
> > >>> -     else
> > >>> -             len += TCPOLEN_MPTCP_ADD_ADDR_BASE;
> > >>> -
> > >>>       /* account for 2 trailing 'nop' options */
> > >>> -     if (addr->port)
> > >>> +     if (port)
> > >>>               len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN;
> > >>>
> > >>>       return len;
> > >>> @@ -798,9 +789,9 @@ static inline int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list)
> > >>>       return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1;
> > >>>  }
> > >>>
> > >>> -bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, struct sk_buff *skb,
> > >>> -                           unsigned int opt_size, unsigned int remaining,
> > >>> -                           struct mptcp_out_options *opts,  u8 *add_addr);
> > >>> +bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
> > >>> +                           struct mptcp_addr_info *saddr, struct mptcp_addr_info *daddr,
> > >>> +                           bool *echo, bool *port);
> > >>>  bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
> > >>>                            struct mptcp_rm_list *rm_list);
> > >>>  int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
> > >>>
> > >>
> > >> --
> > >> Li YongLong
> > >
> >
> > --
> > Li YongLong