Re: [PATCH v3] sctp: Add peeloff-flags socket option

Marcelo Ricardo Leitner
2017-07-01T17:29:19Z

On Fri, Jun 30, 2017 at 01:32:57PM -0400, Neil Horman wrote:
> Based on a request raised on the sctp devel list, there is a need to
> augment the sctp_peeloff operation while specifying the O_CLOEXEC and
> O_NONBLOCK flags (simmilar to the socket syscall). Since modifying the
> SCTP_SOCKOPT_PEELOFF socket option would break user space ABI for existing
> programs, this patch creates a new socket option
> SCTP_SOCKOPT_PEELOFF_FLAGS, which accepts a third flags parameter to
> allow atomic assignment of the socket descriptor flags.
>
> Tested successfully by myself and the requestor
>
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> CC: Vlad Yasevich <vyasevich@gmail.com>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: Andreas Steinmetz <ast@domdv.de>
> CC: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Thanks!

>
> ---
> Change notes:
>
> v2)
>
> * Per Marcellos comments, move to use of get_unused_fd_flags() and
> clean up code to independently set CLOEXEC
>
> * clean up a stray tab
>
> v3)
>
> * Clean up some long lines
> ---
> include/uapi/linux/sctp.h | 6 ++++
> net/sctp/socket.c | 87 +++++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 78 insertions(+), 15 deletions(-)
>
> diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> index ced9d8b..6217ff8 100644
> --- a/include/uapi/linux/sctp.h
> +++ b/include/uapi/linux/sctp.h
> @@ -121,6 +121,7 @@ typedef __s32 sctp_assoc_t;
> #define SCTP_RESET_STREAMS 119
> #define SCTP_RESET_ASSOC 120
> #define SCTP_ADD_STREAMS 121
> +#define SCTP_SOCKOPT_PEELOFF_FLAGS 122
>
> /* PR-SCTP policies */
> #define SCTP_PR_SCTP_NONE 0x0000
> @@ -978,6 +979,11 @@ typedef struct {
> int sd;
> } sctp_peeloff_arg_t;
>
> +typedef struct {
> + sctp_peeloff_arg_t p_arg;
> + unsigned flags;
> +} sctp_peeloff_flags_arg_t;
> +
> /*
> * Peer Address Thresholds socket option
> */
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 7b6e20e..72de049 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -4933,11 +4933,47 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
> }
> EXPORT_SYMBOL(sctp_do_peeloff);
>
> +static int sctp_getsockopt_peeloff_common(struct sock *sk, sctp_peeloff_arg_t *peeloff,
> + struct file **newfile, unsigned flags)
> +{
> + struct socket *newsock;
> + int retval;
> +
> + retval = sctp_do_peeloff(sk, peeloff->associd, &newsock);
> + if (retval < 0)
> + goto out;
> +
> + /* Map the socket to an unused fd that can be returned to the user. */
> + retval = get_unused_fd_flags(flags & SOCK_CLOEXEC);
> + if (retval < 0) {
> + sock_release(newsock);
> + goto out;
> + }
> +
> + *newfile = sock_alloc_file(newsock, 0, NULL);
> + if (IS_ERR(*newfile)) {
> + put_unused_fd(retval);
> + sock_release(newsock);
> + retval = PTR_ERR(*newfile);
> + *newfile = NULL;
> + return retval;
> + }
> +
> + pr_debug("%s: sk:%p, newsk:%p, sd:%d\n", __func__, sk, newsock->sk,
> + retval);
> +
> + peeloff->sd = retval;
> +
> + if (flags & SOCK_NONBLOCK)
> + (*newfile)->f_flags |= O_NONBLOCK;
> +out:
> + return retval;
> +}
> +
> static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval, int __user *optlen)
> {
> sctp_peeloff_arg_t peeloff;
> - struct socket *newsock;
> - struct file *newfile;
> + struct file *newfile = NULL;
> int retval = 0;
>
> if (len < sizeof(sctp_peeloff_arg_t))
> @@ -4946,26 +4982,44 @@ static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval
> if (copy_from_user(&peeloff, optval, len))
> return -EFAULT;
>
> - retval = sctp_do_peeloff(sk, peeloff.associd, &newsock);
> + retval = sctp_getsockopt_peeloff_common(sk, &peeloff, &newfile, 0);
> if (retval < 0)
> goto out;
>
> - /* Map the socket to an unused fd that can be returned to the user. */
> - retval = get_unused_fd_flags(0);
> - if (retval < 0) {
> - sock_release(newsock);
> - goto out;
> + /* Return the fd mapped to the new socket. */
> + if (put_user(len, optlen)) {
> + fput(newfile);
> + put_unused_fd(retval);
> + return -EFAULT;
> }
>
> - newfile = sock_alloc_file(newsock, 0, NULL);
> - if (IS_ERR(newfile)) {
> + if (copy_to_user(optval, &peeloff, len)) {
> + fput(newfile);
> put_unused_fd(retval);
> - sock_release(newsock);
> - return PTR_ERR(newfile);
> + return -EFAULT;
> }
> + fd_install(retval, newfile);
> +out:
> + return retval;
> +}
>
> - pr_debug("%s: sk:%p, newsk:%p, sd:%d\n", __func__, sk, newsock->sk,
> - retval);
> +static int sctp_getsockopt_peeloff_flags(struct sock *sk, int len,
> + char __user *optval, int __user *optlen)
> +{
> + sctp_peeloff_flags_arg_t peeloff;
> + struct file *newfile = NULL;
> + int retval = 0;
> +
> + if (len < sizeof(sctp_peeloff_flags_arg_t))
> + return -EINVAL;
> + len = sizeof(sctp_peeloff_flags_arg_t);
> + if (copy_from_user(&peeloff, optval, len))
> + return -EFAULT;
> +
> + retval = sctp_getsockopt_peeloff_common(sk, &peeloff.p_arg,
> + &newfile, peeloff.flags);
> + if (retval < 0)
> + goto out;
>
> /* Return the fd mapped to the new socket. */
> if (put_user(len, optlen)) {
> @@ -4973,7 +5027,7 @@ static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval
> put_unused_fd(retval);
> return -EFAULT;
> }
> - peeloff.sd = retval;
> +
> if (copy_to_user(optval, &peeloff, len)) {
> fput(newfile);
> put_unused_fd(retval);
> @@ -6758,6 +6812,9 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
> case SCTP_SOCKOPT_PEELOFF:
> retval = sctp_getsockopt_peeloff(sk, len, optval, optlen);
> break;
> + case SCTP_SOCKOPT_PEELOFF_FLAGS:
> + retval = sctp_getsockopt_peeloff_flags(sk, len, optval, optlen);
> + break;
> case SCTP_PEER_ADDR_PARAMS:
> retval = sctp_getsockopt_peer_addr_params(sk, len, optval,
> optlen);
> --
> 2.9.4
>
> --
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