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SubjectRe: [PATCH] um: add a generic "fd" vector transport
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On 08/04/2020 18:07, Marc-André Lureau wrote:
> Hi
>
> On Tue, Apr 7, 2020 at 11:02 PM Anton Ivanov
> <anton.ivanov@cambridgegreys.com> wrote:
>>
>> 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.
>
> So actually, there seems to be a way to do that already:
>
> vec0:transport=fd,fd=N,vec=0

I have forgotten about it (it's been a while since I wrote the drivers).

I will update the docs.

In that case the patch looks good to go, I will ack it shortly.

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


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

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