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

[Geliang Tang <geliangtang@gmail.com>]

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?

>
> >
> >> 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