RE: v5.3.12 SCTP Stream Negotiation Problem

["Fan, Jessie (NSB - CN/Qingdao)" <jessie.fan@xxxxxxxxxxxxxxx>]

Hi, 

I found the SCTP Stream negotiation doesn't work as expected, that is, the local outbound stream and the remote inbound stream comparison seems missing.
For example, when the local outstream(16) is greater than the remote inbound stream(2), 16 is saved and used as the "OUTS", which is shown from /proc/pid/net/sctp/assocs below.
Can anyone help comment?

>From local end point, 16 is set as both the outbound and inbound stream.
>From the remote end point, 2 is set for both the outbound and inbound stream

However, after the association is up, the inbound and outbound stream is set as (2,16), which I think is unexpected.
sh-4.2# cat 1/net/sctp/assocs
ASSOC SOCK STY SST ST HBKT ASSOC-ID TX_QUEUE RX_QUEUE UID INODE LPORT RPORT LADDRS <-> RADDRS HBINT INS OUTS MAXRT T1X T2X RTXC wmema wmemq sndbuf rcvbuf
55dae5bb bb3dec72 0 7 3 0 2415 0 0 504 1223451 2905 3904 xx.xx.xx.xx yy.yy.yy.yy <-> *zz.zz.zz.zz ww.ww.ww.ww 30000 2 16 10 0 0 0 1 0 262144 262144

I further checked the kernel code and found in v5.0, there is still comparison logic: min(outcnt, stream->outcnt) and save the smaller one in the function sctp_stream_alloc_out().
But the logic disappeared in v5.1, and if the "outcnt" is smaller, it's not saved locally.
static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
                                gfp_t gfp)
{
        int ret;

        if (outcnt <= stream->outcnt) //Here is problematic, and the outcnt is not saved locally.
                return 0;

        ret = genradix_prealloc(&stream->out, outcnt, gfp);
        if (ret)
                return ret;

        stream->outcnt = outcnt;
        return 0;
}

Thanks,
Jessie and Chris