SCTP has this operation to peel off associations from a given socket and
create a new socket using this association. We currently have two ways
to use this operation:
- via getsockopt(), on which it will also create and return a file
descriptor for this new socket
- via sctp_do_peeloff(), which is for kernel only
The caveat with using sctp_do_peeloff() directly is that it creates a
dependency to SCTP module, while all other operations are handled via
kernel_{socket,sendmsg,getsockopt...}() interface. This causes the
kernel to load SCTP module even when it's not directly used
This patch then updates SCTP_SOCKOPT_PEELOFF so that for kernel users of
this protocol it will not allocate a file descriptor but instead just
return the socket pointer directly.
If called by an user application it will work as before.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
---
include/uapi/linux/sctp.h | 9 ++++++---
net/sctp/socket.c | 13 +++++++++++++
2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index
ce70fe6b45df3e841c35accbdb6379c16563893c..9e15fc06ba553c7e33f729872bb2dfaa2e21b0d8
100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h
@@ -887,9 +887,12 @@ struct sctp_assoc_stats {
/* This is the structure that is passed as an argument(optval) to
* getsockopt(SCTP_SOCKOPT_PEELOFF).
*/
-typedef struct {
- sctp_assoc_t associd;
- int sd;
+typedef union {
+ struct {
+ sctp_assoc_t associd;
+ int sd;
+ };
+ void *sock;
} sctp_peeloff_arg_t;
/*
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index
f09de7fac2e6acddad8b2e046dbf626e329cb674..ff1138558687e15ee486e84c0916ad81f01ca734
100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4465,6 +4465,19 @@ static int sctp_getsockopt_peeloff(struct sock *sk, int
len, char __user *optval
if (retval < 0)
goto out;
+ /* If the owner of parent sock is the kernel, that is, if a file
+ * descriptor wasn't allocated to it, return the socket pointer
+ * directly instead of allocating a file descriptor.
+ */
+ if (!sk->sk_socket->file) {
+ peeloff.sock = newsock;
+ if (copy_to_user(optval, &peeloff, len)) {
+ sock_release(newsock);
+ return -EFAULT;
+ }
+ return retval;
+ }
+
/* Map the socket to an unused fd that can be returned to the user. */
retval = get_unused_fd_flags(0);
if (retval < 0) {
--
2.4.1
--
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