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SubjectRe: [PATCH] um: add a generic "fd" vector transport
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On 07/04/2020 21:28, Marc-André Lureau wrote:
> 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;
> }
>
>

We should also control enable/disable of recv/sendmmsg as an option here.

It can be made generic and be fed into get_transport_options() in
vector_kern.c as an override.

--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

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