Subject: Re: [PATCHv3 net-next 4/4] sctp: implement sender-side procedures for Add Incoming/Outgoing Streams Request Parameter

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Thu, 19 Jan 2017 20:18:13 -0200

On Thu, Jan 19, 2017 at 03:17:18PM -0500, Neil Horman wrote:
> On Fri, Jan 20, 2017 at 01:19:14AM +0800, Xin Long wrote:
> > This patch is to implement Sender-Side Procedures for the Add
> > Outgoing and Incoming Streams Request Parameter described in
> > rfc6525 section 5.1.5-5.1.6.
> > 
> > It is also to add sockopt SCTP_ADD_STREAMS in rfc6525 section
> > 6.3.4 for users.
> > 
> > Signed-off-by: Xin Long <[email-masked]>
> > ---
> >  include/net/sctp/sctp.h   |  2 +
> >  include/uapi/linux/sctp.h |  7 ++++
> >  net/sctp/socket.c         | 29 ++++++++++++++
> >  net/sctp/stream.c         | 99 +++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 137 insertions(+)
> > 
> > diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> > index b93820f..68ee1a6 100644
> > --- a/include/net/sctp/sctp.h
> > +++ b/include/net/sctp/sctp.h
> > @@ -199,6 +199,8 @@ int sctp_offload_init(void);
> >  int sctp_send_reset_streams(struct sctp_association *asoc,
> >  			    struct sctp_reset_streams *params);
> >  int sctp_send_reset_assoc(struct sctp_association *asoc);
> > +int sctp_send_add_streams(struct sctp_association *asoc,
> > +			  struct sctp_add_streams *params);
> >  
> >  /*
> >   * Module global variables
> > diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> > index c0bd8c3..a91a9cc 100644
> > --- a/include/uapi/linux/sctp.h
> > +++ b/include/uapi/linux/sctp.h
> > @@ -118,6 +118,7 @@ typedef __s32 sctp_assoc_t;
> >  #define SCTP_ENABLE_STREAM_RESET	118
> >  #define SCTP_RESET_STREAMS	119
> >  #define SCTP_RESET_ASSOC	120
> > +#define SCTP_ADD_STREAMS	121
> >  
> >  /* PR-SCTP policies */
> >  #define SCTP_PR_SCTP_NONE	0x0000
> > @@ -1027,4 +1028,10 @@ struct sctp_reset_streams {
> >  	uint16_t srs_stream_list[];	/* list if srs_num_streams is not 0 */
> >  };
> >  
> > +struct sctp_add_streams {
> > +	sctp_assoc_t sas_assoc_id;
> > +	uint16_t sas_instrms;
> > +	uint16_t sas_outstrms;
> > +};
> > +
> >  #endif /* _UAPI_SCTP_H */
> > diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> > index 2c5c9ca..ae0a99e 100644
> > --- a/net/sctp/socket.c
> > +++ b/net/sctp/socket.c
> > @@ -3838,6 +3838,32 @@ static int sctp_setsockopt_reset_assoc(struct sock *sk,
> >  	return retval;
> >  }
> >  
> > +static int sctp_setsockopt_add_streams(struct sock *sk,
> > +				       char __user *optval,
> > +				       unsigned int optlen)
> > +{
> you are going to need to provide some locking here or in sctp_send_add_streams.
> By replacing the in/out streams pointer you run the risk of multiple callers
> modifying the pointers in parallel, or in the sctp state machine reading it
> while you do.

There can't be multiple callers here because the socket is locked before
calling this function, in sctp_setsockopt().
I also don't see how a BH handler, timers or sleeping call (recvmsg)
could trip on this.

  Marcelo