[PATCH net-next 12/13] sctp: consider idata chunks when setting SCTP_MAXSEG

[Marcelo Ricardo Leitner]

When setting SCTP_MAXSEG sock option, it should consider which kind of
data chunk is being used if the asoc is already available, so that the
limit better reflect reality.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
---
 net/sctp/socket.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 
ad8965835d8d51d4eda857b91dfca140710bf7da..2d35c8ea2470e7f5481bb9675ffd233eb3424d91
 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3233,18 +3233,21 @@ static int sctp_setsockopt_maxseg(struct sock *sk, char 
__user *optval, unsigned
                return -EINVAL;
        }
 
+       asoc = sctp_id2assoc(sk, params.assoc_id);
+
        if (val) {
                int min_len, max_len;
+               __u16 datasize = asoc ? sctp_datachk_len(&asoc->stream) :
+                                sizeof(struct sctp_data_chunk);
 
                min_len = sctp_mtu_payload(sp, SCTP_DEFAULT_MINSEGMENT,
-                                          sizeof(struct sctp_data_chunk));
-               max_len = SCTP_MAX_CHUNK_LEN - sizeof(struct sctp_data_chunk);
+                                          datasize);
+               max_len = SCTP_MAX_CHUNK_LEN - datasize;
 
                if (val < min_len || val > max_len)
                        return -EINVAL;
        }
 
-       asoc = sctp_id2assoc(sk, params.assoc_id);
        if (asoc) {
                if (val == 0) {
                        val = asoc->pathmtu - af->net_header_len;
-- 
2.14.3