sctp: Add peeloff-flags socket option

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index ced9d8b..6217ff8 100644 (file)
--- 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 0af103f..1db478e 100644 (file)
--- 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);
@@ -6759,6 +6813,9 @@ 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);