io_uring: add support for sendmsg()

This is done through IORING_OP_SENDMSG. There's a new sqe->msg_flags
for the flags argument, and the msghdr struct is passed in the
sqe->addr field.

We use MSG_DONTWAIT to force an inline fast path if sendmsg() doesn't
block, and punt to async execution if it would have.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1390,6 +1390,43 @@ static int io_sync_file_range(struct io_kiocb *req,
  return 0;
 }
 
+static int io_sendmsg(struct io_kiocb *req, const struct io_uring_sqe *sqe,
+ bool force_nonblock)
+{
+#if defined(CONFIG_NET)
+ struct socket *sock;
+ int ret;
+
+ if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+ return -EINVAL;
+
+ sock = sock_from_file(req->file, &ret);
+ if (sock) {
+ struct user_msghdr __user *msg;
+ unsigned flags;
+
+ flags = READ_ONCE(sqe->msg_flags);
+ if (flags & MSG_DONTWAIT)
+ req->flags |= REQ_F_NOWAIT;
+ else if (force_nonblock)
+ flags |= MSG_DONTWAIT;
+
+ msg = (struct user_msghdr __user *) (unsigned long)
+ READ_ONCE(sqe->addr);
+
+ ret = __sys_sendmsg_sock(sock, msg, flags);
+ if (force_nonblock && ret == -EAGAIN)
+ return ret;
+ }
+
+ io_cqring_add_event(req->ctx, sqe->user_data, ret);
+ io_put_req(req);
+ return 0;
+#else
+ return -EOPNOTSUPP;
+#endif
+}
+
 static void io_poll_remove_one(struct io_kiocb *req)
 {
  struct io_poll_iocb *poll = &req->poll;
@@ -1675,6 +1712,9 @@ static int __io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
  case IORING_OP_SYNC_FILE_RANGE:
  ret = io_sync_file_range(req, s->sqe, force_nonblock);
  break;
+ case IORING_OP_SENDMSG:
+ ret = io_sendmsg(req, s->sqe, force_nonblock);
+ break;
  default:
  ret = -EINVAL;
  break;

include/linux/socket.h

@@ -12,6 +12,7 @@
 
 struct pid;
 struct cred;
+struct socket;
 
 #define __sockaddr_check_size(size) \
  BUILD_BUG_ON(((size) > sizeof(struct __kernel_sockaddr_storage)))
@@ -374,6 +375,9 @@ extern int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg,
 extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
  unsigned int vlen, unsigned int flags,
  bool forbid_cmsg_compat);
+extern long __sys_sendmsg_sock(struct socket *sock,
+ struct user_msghdr __user *msg,
+ unsigned int flags);
 
 /* helpers which do the actual work for syscalls */
 extern int __sys_recvfrom(int fd, void __user *ubuf, size_t size,

include/uapi/linux/io_uring.h

@@ -27,6 +27,7 @@ struct io_uring_sqe {
  __u32 fsync_flags;
  __u16 poll_events;
  __u32 sync_range_flags;
+ __u32 msg_flags;
  };
  __u64 user_data; /* data to be passed back at completion time */
  union {
@@ -58,6 +59,7 @@ struct io_uring_sqe {
 #define IORING_OP_POLL_ADD 6
 #define IORING_OP_POLL_REMOVE 7
 #define IORING_OP_SYNC_FILE_RANGE 8
+#define IORING_OP_SENDMSG 9
 
 /*
  * sqe->fsync_flags

net/socket.c

@@ -2313,6 +2313,13 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
 /*
  * BSD sendmsg interface
  */
+long __sys_sendmsg_sock(struct socket *sock, struct user_msghdr __user *msg,
+ unsigned int flags)
+{
+ struct msghdr msg_sys;
+
+ return ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL, 0);
+}
 
 long __sys_sendmsg(int fd, struct user_msghdr __user *msg, unsigned int flags,
  bool forbid_cmsg_compat)