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Subject[PATCH] um: add a generic "fd" vector transport
Date
Learn to take a pre-opened file-descriptor for vector IO.

Instead of teaching the driver to open a FD in multiple ways, it can
rely on management layer to do it on its behalf. For example, this
allows inheriting a preconfigured device fd or a simple socketpair()
setup, without further arguments, privileges or system access by UML.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
arch/um/drivers/vector_user.c | 59 +++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)

diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index 29fae0456ade..45c1550dbb37 100644
--- a/arch/um/drivers/vector_user.c
+++ b/arch/um/drivers/vector_user.c
@@ -29,6 +29,7 @@
#include <netdb.h>
#include <stdlib.h>
#include <os.h>
+#include <limits.h>
#include <um_malloc.h>
#include "vector_user.h"

@@ -42,6 +43,9 @@
#define TRANS_RAW "raw"
#define TRANS_RAW_LEN strlen(TRANS_RAW)

+#define TRANS_FD "fd"
+#define TRANS_FD_LEN strlen(TRANS_FD)
+
#define VNET_HDR_FAIL "could not enable vnet headers on fd %d"
#define TUN_GET_F_FAIL "tapraw: TUNGETFEATURES failed: %s"
#define L2TPV3_BIND_FAIL "l2tpv3_open : could not bind socket err=%i"
@@ -347,6 +351,59 @@ static struct vector_fds *user_init_unix_fds(struct arglist *ifspec, int id)
return NULL;
}

+static int strtofd(const char *nptr)
+{
+ long fd;
+ char *endptr;
+
+ if (nptr == NULL)
+ return -1;
+
+ errno = 0;
+ fd = strtol(nptr, &endptr, 10);
+ if (nptr == endptr ||
+ errno != 0 ||
+ *endptr != '\0' ||
+ fd < 0 ||
+ fd > INT_MAX) {
+ return -1;
+ }
+ return fd;
+}
+
+static struct vector_fds *user_init_fd_fds(struct arglist *ifspec)
+{
+ int fd = -1;
+ char *fdarg = NULL;
+ struct vector_fds *result = NULL;
+
+ fdarg = uml_vector_fetch_arg(ifspec, "fd");
+ fd = strtofd(fdarg);
+ if (fd == -1) {
+ printk(UM_KERN_ERR "fd open: bad or missing fd argument");
+ goto fd_cleanup;
+ }
+
+ result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
+ if (result == NULL) {
+ printk(UM_KERN_ERR "fd open: allocation failed");
+ goto fd_cleanup;
+ }
+
+ result->rx_fd = fd;
+ result->tx_fd = fd;
+ result->remote_addr_size = 0;
+ result->remote_addr = NULL;
+ return result;
+
+fd_cleanup:
+ if (fd >= 0)
+ os_close_file(fd);
+ if (result != NULL)
+ kfree(result);
+ return NULL;
+}
+
static struct vector_fds *user_init_raw_fds(struct arglist *ifspec)
{
int rxfd = -1, txfd = -1;
@@ -578,6 +635,8 @@ struct vector_fds *uml_vector_user_open(
return user_init_socket_fds(parsed, ID_L2TPV3);
if (strncmp(transport, TRANS_BESS, TRANS_BESS_LEN) == 0)
return user_init_unix_fds(parsed, ID_BESS);
+ if (strncmp(transport, TRANS_FD, TRANS_FD_LEN) == 0)
+ return user_init_fd_fds(parsed);
return NULL;
}

--
2.26.0.106.g9fadedd637
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