Re: [dpdk-dev] [PATCH v6 07/19] vhost: add number of fds to vhost-user messages and use it

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 10/12/2018 11:53 AM, Ilya Maximets wrote:
> On 12.10.2018 11:57, Maxime Coquelin wrote:
>>
>>
>> On 10/12/2018 10:45 AM, Maxime Coquelin wrote:
>>>
>>>
>>> On 10/12/2018 10:43 AM, Maxime Coquelin wrote:
>>>>
>>>>
>>>> On 10/11/2018 05:59 PM, Ilya Maximets wrote:
>>>>> On 11.10.2018 12:24, Maxime Coquelin wrote:
>>>>>> As soon as some ancillary data (fds) are received, it is copied
>>>>>> without checking its length.
>>>>>>
>>>>>> This patch adds the number of fds received to the message,
>>>>>> which is set in read_vhost_message().
>>>>>>
>>>>>> This is preliminary work to support sending fds to Qemu.
>>>>>>
>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>>>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>>>> ---
>>>>>>    lib/librte_vhost/socket.c     | 25 ++++++++++++++++++++-----
>>>>>>    lib/librte_vhost/vhost_user.c |  2 +-
>>>>>>    lib/librte_vhost/vhost_user.h |  4 +++-
>>>>>>    3 files changed, 24 insertions(+), 7 deletions(-)
>>>>>>
>>>>>> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
>>>>>> index d63031747..3b0287a26 100644
>>>>>> --- a/lib/librte_vhost/socket.c
>>>>>> +++ b/lib/librte_vhost/socket.c
>>>>>> @@ -94,18 +94,24 @@ static struct vhost_user vhost_user = {
>>>>>>        .mutex = PTHREAD_MUTEX_INITIALIZER,
>>>>>>    };
>>>>>> -/* return bytes# of read on success or negative val on failure. */
>>>>>> +/*
>>>>>> + * return bytes# of read on success or negative val on failure. Update fdnum
>>>>>> + * with number of fds read.
>>>>>> + */
>>>>>>    int
>>>>>> -read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
>>>>>> +read_fd_message(int sockfd, char *buf, int buflen, int *fds, int max_fds,
>>>>>> +        int *fd_num)
>>>>>>    {
>>>>>>        struct iovec iov;
>>>>>>        struct msghdr msgh;
>>>>>> -    size_t fdsize = fd_num * sizeof(int);
>>>>>> -    char control[CMSG_SPACE(fdsize)];
>>>>>> +    char control[CMSG_SPACE(max_fds * sizeof(int))];
>>>>>>        struct cmsghdr *cmsg;
>>>>>>        int got_fds = 0;
>>>>>> +    int *tmp_fds;
>>>>>>        int ret;
>>>>>> +    *fd_num = 0;
>>>>>> +
>>>>>>        memset(&msgh, 0, sizeof(msgh));
>>>>>>        iov.iov_base = buf;
>>>>>>        iov.iov_len  = buflen;
>>>>>> @@ -131,13 +137,22 @@ read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num)
>>>>>>            if ((cmsg->cmsg_level == SOL_SOCKET) &&
>>>>>>                (cmsg->cmsg_type == SCM_RIGHTS)) {
>>>>>>                got_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
>>>>>> +            if (got_fds > max_fds) {
>>>>>
>>>>> Hmm. I just noticed that 'msg_controllen' is set to receive
>>>>> not more than max_fds descriptors. So, this case should not
>>>>> be possible. We will receive MSG_CTRUNC and return before
>>>>> the loop.
>>>>
>>>> Maybe it is better to remove check for MSG_CTRUNC.
>>> s/remove/rework/
>>>
>>>> IIUC, if MSG_CTRUNC happens, we may have to close anyway the ones
>>>> received.
>>>>
>>>> Do you agree?
>>
>> So it seems that other use of MSG_CTRUNC in DPDK and QEMU does care
>> to close the ones that would have been received and just return an
>> error.
> 
> Did you mean 'does not care'?

Yes, I meant "does not care", sorry.

> 'read_msg()' in lib/librte_eal/common/eal_common_proc.c just returns -1
> and 'slave_read()' in hw/virtio/vhost-user.c does not close fds, because
> 'fdsize' is not set at the time of checking the flag.
> 
>>
>> I propose to do the same for now, an remove the got_fds > max_fds part.
>>
>>>>> +                RTE_LOG(ERR, VHOST_CONFIG,
>>>>>> +                    "Received msg contains more fds than supported\n");
>>>>>> +                tmp_fds = (int *)CMSG_DATA(cmsg);
>>>>>> +                while (got_fds--)
>>>>>> +                    close(tmp_fds[got_fds]);
>>>>>> +                return -1;
>>>>>> +            }
>>>>>> +            *fd_num = got_fds;
>>>>>>                memcpy(fds, CMSG_DATA(cmsg), got_fds * sizeof(int));
>>>>>>                break;
>>>>>>            }
>>>>>>        }
>>>>>>        /* Clear out unused file descriptors */
>>>>>> -    while (got_fds < fd_num)
>>>>>> +    while (got_fds < max_fds)
>>>>>>            fds[got_fds++] = -1;
>>>>>>        return ret;
>>>>>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>>>>>> index 83d3e6321..c1c5f35ff 100644
>>>>>> --- a/lib/librte_vhost/vhost_user.c
>>>>>> +++ b/lib/librte_vhost/vhost_user.c
>>>>>> @@ -1509,7 +1509,7 @@ read_vhost_message(int sockfd, struct VhostUserMsg *msg)
>>>>>>        int ret;
>>>>>>        ret = read_fd_message(sockfd, (char *)msg, VHOST_USER_HDR_SIZE,
>>>>>> -        msg->fds, VHOST_MEMORY_MAX_NREGIONS);
>>>>>> +        msg->fds, VHOST_MEMORY_MAX_NREGIONS, &msg->fd_num);
>>>>>>        if (ret <= 0)
>>>>>>            return ret;
>>>>>> diff --git a/lib/librte_vhost/vhost_user.h b/lib/librte_vhost/vhost_user.h
>>>>>> index 62654f736..9a91d496b 100644
>>>>>> --- a/lib/librte_vhost/vhost_user.h
>>>>>> +++ b/lib/librte_vhost/vhost_user.h
>>>>>> @@ -132,6 +132,7 @@ typedef struct VhostUserMsg {
>>>>>>            VhostUserVringArea area;
>>>>>>        } payload;
>>>>>>        int fds[VHOST_MEMORY_MAX_NREGIONS];
>>>>>> +    int fd_num;
>>>>>>    } __attribute((packed)) VhostUserMsg;
>>>>>>    #define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
>>>>>> @@ -155,7 +156,8 @@ int vhost_user_iotlb_miss(struct virtio_net *dev, uint64_t iova, uint8_t perm);
>>>>>>    int vhost_user_host_notifier_ctrl(int vid, bool enable);
>>>>>>    /* socket.c */
>>>>>> -int read_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num);
>>>>>> +int read_fd_message(int sockfd, char *buf, int buflen, int *fds, int max_fds,
>>>>>> +        int *fd_num);
>>>>>>    int send_fd_message(int sockfd, char *buf, int buflen, int *fds, int fd_num);
>>>>>>    #endif
>>>>>>
>>
>>