On Mon, 2 Mar 2020, Xin Long wrote:
> As it says in rfc6458#section-9.2:
>
> The application uses the sctp_peeloff() call to branch off an
> association into a separate socket. (Note that the semantics are
> somewhat changed from the traditional one-to-one style accept()
> call.) Note also that the new socket is a one-to-one style socket.
> Thus, it will be confined to operations allowed for a one-to-one
> style socket.
>
> Prior to this patch, sctp_peeloff() returned a one-to-many type socket,
> on which some operations are not allowed, like shutdown, as Jere
> reported.
>
> This patch is to change it to return a one-to-one type socket instead.
Thanks for looking into this. I like the patch, and it fixes my simple
test case.
But with this patch, peeled-off sockets are created by copying from a
one-to-many socket to a one-to-one socket. Are you sure that that's
not going to cause any problems? Is it possible that there was a
reason why peeloff wasn't implemented this way in the first place?
With this patch there's no way to create UDP_HIGH_BANDWIDTH style
sockets anymore, so the remaining references should probably be
cleaned up:
./net/sctp/socket.c:1886: if (!sctp_style(sk, UDP_HIGH_BANDWIDTH) && msg->msg_name) {
./net/sctp/socket.c:8522: if (sctp_style(sk, UDP_HIGH_BANDWIDTH))
./include/net/sctp/structs.h:144: SCTP_SOCKET_UDP_HIGH_BANDWIDTH,
This patch disables those checks. The first one ignores a destination
address given to sendmsg() with a peeled-off socket - I don't know
why. The second one prevents listen() on a peeled-off socket.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: Leppanen, Jere (Nokia - FI/Espoo) <jere.leppanen@xxxxxxxxx>
Reported-by: Jere Leppanen <jere.leppanen@xxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/socket.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 1b56fc4..2b55beb 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -88,8 +88,7 @@ static int sctp_send_asconf(struct sctp_association *asoc,
> static int sctp_do_bind(struct sock *, union sctp_addr *, int);
> static int sctp_autobind(struct sock *sk);
> static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
> - struct sctp_association *assoc,
> - enum sctp_socket_type type);
> + struct sctp_association *assoc);
>
> static unsigned long sctp_memory_pressure;
> static atomic_long_t sctp_memory_allocated;
> @@ -4965,7 +4964,7 @@ static struct sock *sctp_accept(struct sock *sk, int flags, int *err, bool kern)
> /* Populate the fields of the newsk from the oldsk and migrate the
> * asoc to the newsk.
> */
> - error = sctp_sock_migrate(sk, newsk, asoc, SCTP_SOCKET_TCP);
> + error = sctp_sock_migrate(sk, newsk, asoc);
> if (error) {
> sk_common_release(newsk);
> newsk = NULL;
> @@ -5711,7 +5710,7 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
> return -EINVAL;
>
> /* Create a new socket. */
> - err = sock_create(sk->sk_family, SOCK_SEQPACKET, IPPROTO_SCTP, &sock);
> + err = sock_create(sk->sk_family, SOCK_STREAM, IPPROTO_SCTP, &sock);
> if (err < 0)
> return err;
>
> @@ -5727,8 +5726,7 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
> /* Populate the fields of the newsk from the oldsk and migrate the
> * asoc to the newsk.
> */
> - err = sctp_sock_migrate(sk, sock->sk, asoc,
> - SCTP_SOCKET_UDP_HIGH_BANDWIDTH);
> + err = sctp_sock_migrate(sk, sock->sk, asoc);
> if (err) {
> sock_release(sock);
> sock = NULL;
> @@ -9453,8 +9451,7 @@ static inline void sctp_copy_descendant(struct sock *sk_to,
> * and its messages to the newsk.
> */
> static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
> - struct sctp_association *assoc,
> - enum sctp_socket_type type)
> + struct sctp_association *assoc)
> {
> struct sctp_sock *oldsp = sctp_sk(oldsk);
> struct sctp_sock *newsp = sctp_sk(newsk);
> @@ -9562,7 +9559,7 @@ static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
> * original UDP-style socket or created with the accept() call on a
> * TCP-style socket..
> */
> - newsp->type = type;
> + newsp->type = SCTP_SOCKET_TCP;
>
> /* Mark the new socket "in-use" by the user so that any packets
> * that may arrive on the association after we've moved it are
> --
> 2.1.0
