[libvirt] [PATCH v6 10/19] utils: Implement function to pass a buffer to send via a fd to virCommand

[Stefan Berger]

On 7/25/19 1:34 PM, Daniel P. Berrangé wrote:
> On Thu, Jul 25, 2019 at 10:30:24AM -0400, Stefan Berger wrote:
>> Implement virCommandSetSendBuffer() that allows the caller to pass a
>> file descriptor and buffer to virCommand. virCommand will write the
>> buffer into the file descriptor. That file descriptor could be the
>> write end of a pipe or one of the file descriptors of a socketpair.
>> The other file descriptor should be passed to the launched process to
>> read the data from.
>>
>> Only implement the function to allocate memory for send buffers
>> and to free them later on.
>>
>> Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
>> Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>
>> ---
>>   src/libvirt_private.syms |  1 +
>>   src/util/vircommand.c    | 76 ++++++++++++++++++++++++++++++++++++++++
>>   src/util/vircommand.h    |  5 +++
>>   3 files changed, 82 insertions(+)
>>
>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>> index cf80ea3e44..e6249caa80 100644
>> --- a/src/libvirt_private.syms
>> +++ b/src/libvirt_private.syms
>> @@ -1725,6 +1725,7 @@ virCommandSetOutputFD;
>>   virCommandSetPidFile;
>>   virCommandSetPreExecHook;
>>   virCommandSetSELinuxLabel;
>> +virCommandSetSendBuffer;
>>   virCommandSetUID;
>>   virCommandSetUmask;
>>   virCommandSetWorkingDirectory;
>> diff --git a/src/util/vircommand.c b/src/util/vircommand.c
>> index e10ca3eb7c..5dee730826 100644
>> --- a/src/util/vircommand.c
>> +++ b/src/util/vircommand.c
>> @@ -76,6 +76,16 @@ struct _virCommandFD {
>>       unsigned int flags;
>>   };
>>   
>> +typedef struct _virCommandSendBuffer virCommandSendBuffer;
>> +typedef virCommandSendBuffer *virCommandSendBufferPtr;
>> +
>> +struct _virCommandSendBuffer {
>> +    int fd;
>> +    unsigned char *buffer;
>> +    size_t buflen;
>> +    off_t offset;
>> +};
>> +
>>   struct _virCommand {
>>       int has_error; /* ENOMEM on allocation failure, -1 for anything else.  */
>>   
>> @@ -135,6 +145,9 @@ struct _virCommand {
>>       char *appArmorProfile;
>>   #endif
>>       int mask;
>> +
>> +    virCommandSendBufferPtr sendBuffers;
>> +    size_t numSendBuffers;
>>   };
>>   
>>   /* See virCommandSetDryRun for description for this variable */
>> @@ -1728,6 +1741,67 @@ virCommandSetWorkingDirectory(virCommandPtr cmd, const char *pwd)
>>   }
>>   
>>   
>> +static int
>> +virCommandGetNumSendBuffers(virCommandPtr cmd)
>> +{
>> +    return cmd->numSendBuffers;
>> +}
>> +
>> +
>> +static void
>> +virCommandFreeSendBuffers(virCommandPtr cmd)
>> +{
>> +    size_t i;
>> +
>> +    for (i = 0; i < virCommandGetNumSendBuffers(cmd); i++) {
>> +        VIR_FORCE_CLOSE(cmd->sendBuffers[i].fd);
>> +        VIR_FREE(cmd->sendBuffers[i].buffer);
>> +    }
>> +    VIR_FREE(cmd->sendBuffers);
>> +}
>> +
>> +
>> +/**
>> + * virCommandSetSendBuffer
>> + * @cmd: the command to modify
>> + *
>> + * Pass a buffer to virCommand that will be written into the
>> + * given file descriptor. The buffer will be freed automatically
>> + * and the file descriptor closed.
>> + */
>> +int
>> +virCommandSetSendBuffer(virCommandPtr cmd,
>> +                        int fd,
>> +                        unsigned char *buffer, size_t buflen)
>> +{
>> +    size_t i = virCommandGetNumSendBuffers(cmd);
>> +
>> +    if (!cmd || cmd->has_error)
>> +        return -1;
>> +
>> +    if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) {
>> +        virReportSystemError(errno, "%s",
>> +                             _("fcntl failed to set O_NONBLOCK"));
>> +        cmd->has_error = errno;
>> +        return -1;
>> +    }
> I hit a build failure on mingw with this change, because F_SETFL
> doesn't exist.
>
> None of the vircommand code actually runs on windows, so we just
> need to stub this method out to immediately return -1 with
> has_error set to ENOSUPP i guess.

Fixed them with ENOTSUP. Will post v7 assuming you will add your R-b's 
then...


    Stefan