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....@gmail.com> wrote: > > > > On Wed, Sep 11, 2019 at 5:03 PM David Laight <david.lai...@aculab.com> > > wrote: > > > > > > From: Xin Long [mailto:lucien....@gmail.com] > > > > Sent: 11 September 2019 09:52 > > > > On Tue, Sep 10, 2019 at 9:19 PM David Laight <david.lai...@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....@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) >
