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From: Yonglong Li <liyonglong@chinatelecom.cn>
To: Geliang Tang <geliangtang@gmail.com>
Cc: mptcp@lists.linux.dev
Subject: Re: [MPTCP][PATCH mptcp-next] Squash to "mptcp: build ADD_ADDR/echo-ADD_ADDR option according pm.add_signal"
Date: Mon, 12 Jul 2021 17:14:14 +0800	[thread overview]
Message-ID: <3f3c3065-8a08-fc0c-da8b-0e210097b136@chinatelecom.cn> (raw)
In-Reply-To: <CA+WQbwsuJTtVZ_hW1K25a4YOkSs7DGKOnjt=escT66QQg8WjRQ@mail.gmail.com>



On 2021/7/12 16:44, Geliang Tang wrote:
> 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?
yep. In this case the squash-to patch is ok. But I think between "drop other suboptions" checks and
mptcp_pm_add_addr_signal the race still exist.

==> an add addr event (pm.addr_signal == MPTCP_ADD_ADDR_SIGNAL)
==> "drop other suboptions" checks will use MPTCP_ADD_ADDR_SIGNAL to check
==> an echo add addr event trigger (pm.addr_signal == MPTCP_ADD_ADDR_SIGNAL | MPTCP_ADD_ADDR_ECHO )
==> call mptcp_pm_add_addr_signal, MPTCP_ADD_ADDR_ECHO will be clear in pm.addr_signal
==> process MPTCP_ADD_ADDR_ECHO event.

WDYT?

> 
>>
>>>
>>>> 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
> 
> 

-- 
Li YongLong

  parent reply	other threads:[~2021-07-12  9:14 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-11 15:15 [MPTCP][PATCH mptcp-next] Squash to "mptcp: make MPTCP_ADD_ADDR_SIGNAL and MPTCP_ADD_ADDR_ECHO separate" Geliang Tang
2021-07-11 15:15 ` [MPTCP][PATCH mptcp-next] Squash to "mptcp: fix ADD_ADDR and RM_ADDR maybe flush addr_signal each other" Geliang Tang
2021-07-12  9:55   ` Yonglong Li
2021-07-12 10:34     ` Geliang Tang
2021-07-12 22:27       ` Mat Martineau
2021-07-11 15:15 ` [MPTCP][PATCH mptcp-next] Squash to "mptcp: build ADD_ADDR/echo-ADD_ADDR option according pm.add_signal" Geliang Tang
2021-07-12  1:34   ` Yonglong Li
2021-07-12  7:33     ` Geliang Tang
2021-07-12  8:06       ` Yonglong Li
2021-07-12  8:44         ` Geliang Tang
2021-07-12  9:07           ` Geliang Tang
2021-07-12  9:21             ` Yonglong Li
2021-07-12  9:14           ` Yonglong Li [this message]
2021-07-12  9:29             ` Geliang Tang
2021-07-12  9:44               ` Yonglong Li
2021-07-12 10:34                 ` Geliang Tang
2021-07-12 22:10 ` [MPTCP][PATCH mptcp-next] Squash to "mptcp: make MPTCP_ADD_ADDR_SIGNAL and MPTCP_ADD_ADDR_ECHO separate" Mat Martineau

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