Re: [PATCH net v3] sctp: socket: remove unused 'err' parameter from sctp_skb_recv_datagram

[Xin Long]

On Fri, Jul 17, 2026 at 4:21 AM luoqing <l1138897701@xxxxxxx> wrote:
>
> From: luoqing <luoqing@xxxxxxxxxx>
>
> The 'err' parameter in sctp_skb_recv_datagram() is never used by any
> of its callers. Both sctp_recvmsg() and sctp_ulpevent_read_nxtinfo()
> pass the address of a local variable but never check its value after
> the function returns, rendering the parameter completely useless.
>
> Remove the unused parameter to simplify the function signature and
> eliminate dead code.
>
> Signed-off-by: luoqing <luoqing@xxxxxxxxxx>
> ---
>  include/net/sctp/sctp.h |  2 +-
>  net/sctp/socket.c       | 10 +++-------
>  net/sctp/ulpevent.c     |  3 +--
>  3 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index d50c27812504..b86d50d6b146 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -97,7 +97,7 @@ void sctp_sock_rfree(struct sk_buff *skb);
>
>  extern struct percpu_counter sctp_sockets_allocated;
>  int sctp_asconf_mgmt(struct sctp_sock *, struct sctp_sockaddr_entry *);
> -struct sk_buff *sctp_skb_recv_datagram(struct sock *, int, int *);
> +struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags);
>
>  typedef int (*sctp_callback_t)(struct sctp_endpoint *, struct sctp_transport *, void *);
>  void sctp_transport_walk_start(struct rhashtable_iter *iter);
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index c7b9e325ec1c..3804382d78e0 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -2123,7 +2123,7 @@ static int sctp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>                 goto out;
>         }
>
> -       skb = sctp_skb_recv_datagram(sk, flags, &err);
> +       skb = sctp_skb_recv_datagram(sk, flags);
>         if (!skb)
>                 goto out;
>
> @@ -9082,7 +9082,7 @@ static int sctp_wait_for_packet(struct sock *sk, int *err, long *timeo_p)
>   * Note: This is pretty much the same routine as in core/datagram.c
>   * with a few changes to make lksctp work.
>   */
> -struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags, int *err)
> +struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags)
>  {
>         int error;
>         struct sk_buff *skb;
> @@ -9120,17 +9120,13 @@ struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags, int *err)
>                 if (sk->sk_shutdown & RCV_SHUTDOWN)
>                         break;
>
> -
>                 /* User doesn't want to wait.  */
>                 error = -EAGAIN;
>                 if (!timeo)
>                         goto no_packet;
> -       } while (sctp_wait_for_packet(sk, err, &timeo) == 0);
> -
> -       return NULL;
> +       } while (sctp_wait_for_packet(sk, &error, &timeo) == 0);
>
>  no_packet:
> -       *err = error;
>         return NULL;
>  }
>
> diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
> index 8920ca92a011..8ed51a15c3a4 100644
> --- a/net/sctp/ulpevent.c
> +++ b/net/sctp/ulpevent.c
> @@ -1061,9 +1061,8 @@ void sctp_ulpevent_read_nxtinfo(const struct sctp_ulpevent *event,
>                                 struct sock *sk)
>  {
>         struct sk_buff *skb;
> -       int err;
>
> -       skb = sctp_skb_recv_datagram(sk, MSG_PEEK | MSG_DONTWAIT, &err);
> +       skb = sctp_skb_recv_datagram(sk, MSG_PEEK | MSG_DONTWAIT);
>         if (skb != NULL) {
>                 __sctp_ulpevent_read_nxtinfo(sctp_skb2event(skb),
>                                              msghdr, skb);
> --
> 2.25.1
>
I think it's used at [1] in sctp_recvmsg():

        skb = sctp_skb_recv_datagram(sk, flags, &err);
        if (!skb)
                goto out;
...

out:
        release_sock(sk);
        return err;   <------ [1]

Thanks.