Re: [PATCH v2 1/3] qio: add support for SO_PEERCRED for socket channel

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/1/23 11:20, Daniel P. Berrangé wrote:
> On Tue, Oct 31, 2023 at 03:46:01PM +0100, Anthony Harivel wrote:
>> The function qio_channel_get_peercred() returns a pointer to the
>> credentials of the peer process connected to this socket.
>>
>> This credentials structure is defined in <sys/socket.h> as follows:
>>
>> struct ucred {
>> 	pid_t pid;    /* Process ID of the sending process */
>> 	uid_t uid;    /* User ID of the sending process */
>> 	gid_t gid;    /* Group ID of the sending process */
>> };
>>
>> The use of this function is possible only for connected AF_UNIX stream
>> sockets and for AF_UNIX stream and datagram socket pairs.
>>
>> Signed-off-by: Anthony Harivel <aharivel@redhat.com>
>> ---
>>   include/io/channel.h | 20 ++++++++++++++++++++
>>   io/channel-socket.c  | 17 +++++++++++++++++
>>   io/channel.c         | 12 ++++++++++++
>>   3 files changed, 49 insertions(+)
>>
>> diff --git a/include/io/channel.h b/include/io/channel.h
>> index 5f9dbaab65b0..99c02d61c3d9 100644
>> --- a/include/io/channel.h
>> +++ b/include/io/channel.h
>> @@ -149,6 +149,9 @@ struct QIOChannelClass {
>>                                     void *opaque);
>>       int (*io_flush)(QIOChannel *ioc,
>>                       Error **errp);
>> +    void (*io_peercred)(QIOChannel *ioc,
>> +                        struct ucred *cred,
>> +                        Error **errp);
> 
> This isn't going to fly. 'struct ucred' is Linux specific, so this won't
> compile on macOS, Windows, *BSD, and we don't really want a huge #ifdef
> ladder in these APIs. This will need to explode the struct and return
> the individual fields that are present instead, and the impl side must
> compile on other OS, even if its just stubbed out to return an error.

I would further reduce it to to io_peerpid, because the BSDs can only 
provide the peer uid and gid.

Paolo