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

[Yonglong Li <liyonglong@chinatelecom.cn>]

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.

> 
>> 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