[CRIU] [PATCH 3/3] unix: allow --external unix[ino]:string

[Ruslan Kuprieiev]

Doing it on dump adds a benefit of not having to remember anything for 
restore.
If this option will be available only on restore, I would have to 
remember socket ino till
restore to set up this option, which I'm trying to avoid altogether.

Can we maybe have this option both on dump and restore?

On 01/11/2017 12:36 PM, Pavel Emelyanov wrote:
> On 01/10/2017 04:01 PM, Ruslan Kuprieiev wrote:
>> On dump, if --external unix[ino]:foo is specified, criu will treat
>> specified unix socket almost the same
>> way it handles criu service socket. It will dump it as closed and will
>> put "foo" string into images, to put
>> that "foo" string into that socket on restore. This is almost identical
>> to what criu does with service
>> socket, but instead of putting a Criu_Resp message into it on restore,
>> it puts an arbitrary string.
> Ah, I see. I think, that adding a message to send after restore should be
> a restore-time option and the string in question shouldn't sit in images.
> Can you tune the patches to make it so?
>
>> On 01/10/2017 02:56 PM, Pavel Emelyanov wrote:
>>> On 01/05/2017 03:42 PM, Ruslan Kuprieiev wrote:
>>>
>>> Can you elaborate what this option should do? It's not 100% clear
>>> from the code.
>>>
>>>> Needles to say that it's useful for debug, but this is also
>>>> very useful when you syncronise checkpoint/restore whith a
>>>> dumpee using unix socketpair and want it to painlessly
>>>> receive notification on restore.
>>>>
>>>> Signed-off-by: Ruslan Kuprieiev <rkuprieiev at cloudlinux.com>
>>>> ---
>>>>    criu/sk-unix.c       | 23 +++++++++++++++++++++--
>>>>    images/sk-unix.proto |  5 +++++
>>>>    2 files changed, 26 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/criu/sk-unix.c b/criu/sk-unix.c
>>>> index 5cbe07a..4527dd6 100644
>>>> --- a/criu/sk-unix.c
>>>> +++ b/criu/sk-unix.c
>>>> @@ -263,6 +263,8 @@ static int dump_one_unix_fd(int lfd, u32 id, const struct fd_parms *p)
>>>>    	SkOptsEntry *skopts;
>>>>    	FilePermsEntry *perms;
>>>>    	FownEntry *fown;
>>>> +	char buf[PATH_MAX];
>>>> +	char *ext = NULL;
>>>>    
>>>>    	ue = xmalloc(sizeof(UnixSkEntry) +
>>>>    			sizeof(SkOptsEntry) +
>>>> @@ -322,6 +324,16 @@ static int dump_one_unix_fd(int lfd, u32 id, const struct fd_parms *p)
>>>>    		ue->uflags |= USK_SERVICE;
>>>>    	}
>>>>    
>>>> +	/* Same as with service_sk, but for custom sockets */
>>>> +	snprintf(buf, sizeof(buf), "unix[%u]", ue->peer);
>>>> +	ext = external_lookup_by_key(buf);
>>>> +	if (unlikely(!IS_ERR_OR_NULL(ext))) {
>>>> +		ue->state = TCP_CLOSE;
>>>> +		ue->peer = 0;
>>>> +		ue->uflags |= USK_SERVICE;
>>>> +		ue->stub = (void *)strtok(ext, ":");
>>>> +	}
>>>> +
>>>>    	if (sk->namelen && *sk->name) {
>>>>    		ue->file_perms = perms;
>>>>    
>>>> @@ -1139,8 +1151,15 @@ static int open_unixsk_standalone(struct unix_sk_info *ui)
>>>>    			return -1;
>>>>    		}
>>>>    
>>>> -		if (send_criu_dump_resp(sks[1], true, true) == -1)
>>>> -			return -1;
>>>> +		if (ui->ue->stub) {
>>>> +			unsigned int l;
>>>> +			l = strlen(ui->ue->stub);
>>>> +			if (write(sks[1], ui->ue->stub, l) != l)
>>>> +				return -1;
>>>> +		} else {
>>>> +			if (send_criu_dump_resp(sks[1], true, true) == -1)
>>>> +				return -1;
>>>> +		}
>>>>    
>>>>    		close(sks[1]);
>>>>    		sk = sks[0];
>>>> diff --git a/images/sk-unix.proto b/images/sk-unix.proto
>>>> index 3026214..4437700 100644
>>>> --- a/images/sk-unix.proto
>>>> +++ b/images/sk-unix.proto
>>>> @@ -48,4 +48,9 @@ message unix_sk_entry {
>>>>    	 */
>>>>    	optional string			name_dir	= 14;
>>>>    	optional bool			deleted		= 15;
>>>> +
>>>> +	/*
>>>> +	 * Stub to put into service socket on restore
>>>> +	 */
>>>> +        optional string			stub		= 16;
>>>>    }
>>>>
>> .
>>