v4.19.13 snapshot.
diff --git a/arch/um/drivers/slirp_user.c b/arch/um/drivers/slirp_user.c
new file mode 100644
index 0000000..98b6a41
--- /dev/null
+++ b/arch/um/drivers/slirp_user.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL.
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <net_user.h>
+#include <os.h>
+#include "slirp.h"
+
+static int slirp_user_init(void *data, void *dev)
+{
+ struct slirp_data *pri = data;
+
+ pri->dev = dev;
+ return 0;
+}
+
+struct slirp_pre_exec_data {
+ int stdin_fd;
+ int stdout_fd;
+};
+
+static void slirp_pre_exec(void *arg)
+{
+ struct slirp_pre_exec_data *data = arg;
+
+ if (data->stdin_fd != -1)
+ dup2(data->stdin_fd, 0);
+ if (data->stdout_fd != -1)
+ dup2(data->stdout_fd, 1);
+}
+
+static int slirp_tramp(char **argv, int fd)
+{
+ struct slirp_pre_exec_data pe_data;
+ int pid;
+
+ pe_data.stdin_fd = fd;
+ pe_data.stdout_fd = fd;
+ pid = run_helper(slirp_pre_exec, &pe_data, argv);
+
+ return pid;
+}
+
+static int slirp_open(void *data)
+{
+ struct slirp_data *pri = data;
+ int fds[2], pid, err;
+
+ err = os_pipe(fds, 1, 1);
+ if (err)
+ return err;
+
+ err = slirp_tramp(pri->argw.argv, fds[1]);
+ if (err < 0) {
+ printk(UM_KERN_ERR "slirp_tramp failed - errno = %d\n", -err);
+ goto out;
+ }
+ pid = err;
+
+ pri->slave = fds[1];
+ pri->slip.pos = 0;
+ pri->slip.esc = 0;
+ pri->pid = err;
+
+ return fds[0];
+out:
+ close(fds[0]);
+ close(fds[1]);
+ return err;
+}
+
+static void slirp_close(int fd, void *data)
+{
+ struct slirp_data *pri = data;
+ int err;
+
+ close(fd);
+ close(pri->slave);
+
+ pri->slave = -1;
+
+ if (pri->pid<1) {
+ printk(UM_KERN_ERR "slirp_close: no child process to shut "
+ "down\n");
+ return;
+ }
+
+#if 0
+ if (kill(pri->pid, SIGHUP)<0) {
+ printk(UM_KERN_ERR "slirp_close: sending hangup to %d failed "
+ "(%d)\n", pri->pid, errno);
+ }
+#endif
+ err = helper_wait(pri->pid);
+ if (err < 0)
+ return;
+
+ pri->pid = -1;
+}
+
+int slirp_user_read(int fd, void *buf, int len, struct slirp_data *pri)
+{
+ return slip_proto_read(fd, buf, len, &pri->slip);
+}
+
+int slirp_user_write(int fd, void *buf, int len, struct slirp_data *pri)
+{
+ return slip_proto_write(fd, buf, len, &pri->slip);
+}
+
+const struct net_user_info slirp_user_info = {
+ .init = slirp_user_init,
+ .open = slirp_open,
+ .close = slirp_close,
+ .remove = NULL,
+ .add_address = NULL,
+ .delete_address = NULL,
+ .mtu = BUF_SIZE,
+ .max_packet = BUF_SIZE,
+};