um: Add a generic "fd" vector transport

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>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index aa28e9e..c4a0f26 100644 (file)
--- 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 @@ unix_cleanup:
        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;
 }