From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Xin Long <lucien.xin@gmail.com>
Cc: David Laight <David.Laight@aculab.com>,
network dev <netdev@vger.kernel.org>,
"linux-sctp@vger.kernel.org" <linux-sctp@vger.kernel.org>,
Neil Horman <nhorman@tuxdriver.com>,
"davem@davemloft.net" <davem@davemloft.net>
Subject: Re: [PATCH net-next 5/5] sctp: add spt_pathcpthld in struct sctp_paddrthlds
Date: Wed, 11 Sep 2019 09:56:09 -0300 [thread overview]
Message-ID: <20190911125609.GC3499@localhost.localdomain> (raw)
In-Reply-To: <CADvbK_dqNas+vwP2t3LqWyabNnzRDO=PZPe4p+zE-vQJTnfKpA@mail.gmail.com>
On Wed, Sep 11, 2019 at 05:38:33PM +0800, Xin Long wrote:
> On Wed, Sep 11, 2019 at 5:21 PM Xin Long <lucien.xin@gmail.com> wrote:
> >
> > On Wed, Sep 11, 2019 at 5:03 PM David Laight <David.Laight@aculab.com> wrote:
> > >
> > > From: Xin Long [mailto:lucien.xin@gmail.com]
> > > > Sent: 11 September 2019 09:52
> > > > On Tue, Sep 10, 2019 at 9:19 PM David Laight <David.Laight@aculab.com> wrote:
> > > > >
> > > > > From: Xin Long
> > > > > > Sent: 09 September 2019 08:57
> > > > > > Section 7.2 of rfc7829: "Peer Address Thresholds (SCTP_PEER_ADDR_THLDS)
> > > > > > Socket Option" extends 'struct sctp_paddrthlds' with 'spt_pathcpthld'
> > > > > > added to allow a user to change ps_retrans per sock/asoc/transport, as
> > > > > > other 2 paddrthlds: pf_retrans, pathmaxrxt.
> > > > > >
> > > > > > Note that ps_retrans is not allowed to be greater than pf_retrans.
> > > > > >
> > > > > > Signed-off-by: Xin Long <lucien.xin@gmail.com>
> > > > > > ---
> > > > > > include/uapi/linux/sctp.h | 1 +
> > > > > > net/sctp/socket.c | 10 ++++++++++
> > > > > > 2 files changed, 11 insertions(+)
> > > > > >
> > > > > > diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> > > > > > index a15cc28..dfd81e1 100644
> > > > > > --- a/include/uapi/linux/sctp.h
> > > > > > +++ b/include/uapi/linux/sctp.h
> > > > > > @@ -1069,6 +1069,7 @@ struct sctp_paddrthlds {
> > > > > > struct sockaddr_storage spt_address;
> > > > > > __u16 spt_pathmaxrxt;
> > > > > > __u16 spt_pathpfthld;
> > > > > > + __u16 spt_pathcpthld;
> > > > > > };
> > > > > >
> > > > > > /*
> > > > > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> > > > > > index 5e2098b..5b9774d 100644
> > > > > > --- a/net/sctp/socket.c
> > > > > > +++ b/net/sctp/socket.c
> > > > > > @@ -3954,6 +3954,9 @@ static int sctp_setsockopt_paddr_thresholds(struct sock *sk,
> > > > >
> > > > > This code does:
> > > > > if (optlen < sizeof(struct sctp_paddrthlds))
> > > > > return -EINVAL;
> > > > here will become:
> > > >
> > > > if (optlen >= sizeof(struct sctp_paddrthlds)) {
> > > > optlen = sizeof(struct sctp_paddrthlds);
> > > > } else if (optlen >= ALIGN(offsetof(struct sctp_paddrthlds,
> > > > spt_pathcpthld), 4))
> > > > optlen = ALIGN(offsetof(struct sctp_paddrthlds,
> > > > spt_pathcpthld), 4);
> > > > val.spt_pathcpthld = 0xffff;
> > > > else {
> > > > return -EINVAL;
> > > > }
> > >
> > > Hmmm...
> > > If the kernel has to default 'val.spt_pathcpthld = 0xffff'
> > > then recompiling an existing application with the new uapi
> > > header is going to lead to very unexpected behaviour.
> > >
> > > The best you can hope for is that the application memset the
> > > structure to zero.
> > > But more likely it is 'random' on-stack data.
> > 0xffff is a value to disable the feature 'Primary Path Switchover'.
> > you're right that user might set it to zero unexpectly with their
> > old application rebuilt.
> >
> > A safer way is to introduce "sysctl net.sctp.ps_retrans", it won't
> > matter if users set spt_pathcpthld properly when they're not aware
> > of this feature, like "sysctl net.sctp.pF_retrans". Looks better?
> Sorry for confusing, "sysctl net.sctp.ps_retrans" is already there
> (its value is 0xffff by default),
> we just need to do this in sctp_setsockopt_paddr_thresholds():
>
> if (copy_from_user(&val, (struct sctp_paddrthlds __user *)optval,
> optlen))
> return -EFAULT;
>
> if (sock_net(sk)->sctp.ps_retrans == 0xffff)
> val.spt_pathcpthld = 0xffff;
I'm confused with the snippets, but if I got them right, this is after
dealing with proper len and could leave val.spt_pathcpthld
uninitialized if the application used the old format and sysctl is !=
0xffff.
>
> if (val.spt_pathpfthld > val.spt_pathcpthld)
> return -EINVAL;
>
> >
> > >
> > > David
> > >
> > > -
> > > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> > > Registration No: 1397386 (Wales)
>
next prev parent reply other threads:[~2019-09-11 12:56 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 7:56 [PATCH net-next 0/5] sctp: update from rfc7829 Xin Long
2019-09-09 7:56 ` [PATCH net-next 1/5] sctp: add SCTP_ADDR_POTENTIALLY_FAILED notification Xin Long
2019-09-09 7:56 ` [PATCH net-next 2/5] sctp: add pf_expose per netns and sock and asoc Xin Long
2019-09-09 7:56 ` [PATCH net-next 3/5] sctp: add SCTP_EXPOSE_POTENTIALLY_FAILED_STATE sockopt Xin Long
2019-09-09 7:56 ` [PATCH net-next 4/5] sctp: add support for Primary Path Switchover Xin Long
2019-09-09 7:56 ` [PATCH net-next 5/5] sctp: add spt_pathcpthld in struct sctp_paddrthlds Xin Long
2019-09-10 13:19 ` David Laight
2019-09-11 8:51 ` Xin Long
2019-09-11 9:03 ` David Laight
2019-09-11 9:21 ` Xin Long
2019-09-11 9:38 ` Xin Long
2019-09-11 12:56 ` Marcelo Ricardo Leitner [this message]
2019-09-11 17:47 ` Xin Long
2019-09-12 22:51 ` Marcelo Ricardo Leitner
2019-09-13 8:36 ` David Laight
2019-09-13 13:19 ` 'Marcelo Ricardo Leitner'
2019-09-13 13:31 ` David Laight
2019-09-13 13:40 ` 'Marcelo Ricardo Leitner'
2019-09-10 17:27 ` David Miller
2019-09-11 8:14 ` Xin Long
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