io_uring: Introduce IORING_OP_BIND

IORING_OP_BIND provides the semantic of bind(2) via io_uring.  While
this is an essentially synchronous system call, the main point is to
enable a network path to execute fully with io_uring registered and
descriptorless files.
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/20240614163047.31581-3-krisman@suse.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/uapi/linux/io_uring.h

@@ -257,6 +257,7 @@ enum io_uring_op {
 	IORING_OP_FUTEX_WAITV,
 	IORING_OP_FIXED_FD_INSTALL,
 	IORING_OP_FTRUNCATE,
+	IORING_OP_BIND,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,

io_uring/net.c

@@ -51,6 +51,11 @@ struct io_connect {
 	bool				seen_econnaborted;
 };
 
+struct io_bind {
+	struct file			*file;
+	int				addr_len;
+};
+
 struct io_sr_msg {
 	struct file			*file;
 	union {
@@ -1715,6 +1720,37 @@ int io_connect(struct io_kiocb *req, unsigned int issue_flags)
 	return IOU_OK;
 }
 
+int io_bind_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_bind *bind = io_kiocb_to_cmd(req, struct io_bind);
+	struct sockaddr __user *uaddr;
+	struct io_async_msghdr *io;
+
+	if (sqe->len || sqe->buf_index || sqe->rw_flags || sqe->splice_fd_in)
+		return -EINVAL;
+
+	uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	bind->addr_len =  READ_ONCE(sqe->addr2);
+
+	io = io_msg_alloc_async(req);
+	if (unlikely(!io))
+		return -ENOMEM;
+	return move_addr_to_kernel(uaddr, bind->addr_len, &io->addr);
+}
+
+int io_bind(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_bind *bind = io_kiocb_to_cmd(req, struct io_bind);
+	struct io_async_msghdr *io = req->async_data;
+	int ret;
+
+	ret = __sys_bind_socket(sock_from_file(req->file),  &io->addr, bind->addr_len);
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return 0;
+}
+
 void io_netmsg_cache_free(const void *entry)
 {
 	struct io_async_msghdr *kmsg = (struct io_async_msghdr *) entry;

io_uring/net.h

@@ -49,6 +49,9 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags);
 int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 void io_send_zc_cleanup(struct io_kiocb *req);
 
+int io_bind_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_bind(struct io_kiocb *req, unsigned int issue_flags);
+
 void io_netmsg_cache_free(const void *entry);
 #else
 static inline void io_netmsg_cache_free(const void *entry)

io_uring/opdef.c

@@ -495,6 +495,16 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_ftruncate_prep,
 		.issue			= io_ftruncate,
 	},
+	[IORING_OP_BIND] = {
+#if defined(CONFIG_NET)
+		.needs_file		= 1,
+		.prep			= io_bind_prep,
+		.issue			= io_bind,
+		.async_size		= sizeof(struct io_async_msghdr),
+#else
+		.prep			= io_eopnotsupp_prep,
+#endif
+	},
 };
 
 const struct io_cold_def io_cold_defs[] = {
@@ -716,6 +726,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_FTRUNCATE] = {
 		.name			= "FTRUNCATE",
 	},
+	[IORING_OP_BIND] = {
+		.name			= "BIND",
+	},
 };
 
 const char *io_uring_get_opcode(u8 opcode)