[CRIU] [PATCH] unix: Add support for restoring unix receive queue for DGRAM sockets

[Andrew Vagin]

On Thu, Nov 26, 2015 at 01:41:23PM +0300, Kirill Tkhai wrote:
> Restore a receive queue in cases of:
> 
> 1)socketpair with closed second end;
> 2)peer-less "listening" socket, who is a peer for others.
> 
> The only hack we use here is the connect with AF_UNSPEC family,
> which clears peer of restoring socket. See unix_dgram_connect()
> for the details.
> 
> This also makes socket_close_data test working.

so we need to delete test/zdtm/live/static/socket_close_data.desc

The following command should run the test
python test/zdtm.py run -T zdtm/live/static/socket_close_data

And I think we need to check a case when a dgram socket is bond to an
address and another socket is connected to it.

> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  sk-unix.c |   22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/sk-unix.c b/sk-unix.c
> index 91e4263..011739d 100644
> --- a/sk-unix.c
> +++ b/sk-unix.c
> @@ -1133,6 +1133,28 @@ static int open_unixsk_standalone(struct unix_sk_info *ui)
>  
>  		close(sks[1]);
>  		sk = sks[0];
> +	} else if (ui->ue->type == SOCK_DGRAM && !ui->ue->peer) {
> +		struct sockaddr_un addr;
> +		int sks[2];
> +
> +		if (socketpair(PF_UNIX, ui->ue->type, 0, sks) < 0) {
> +			pr_perror("Can't create socketpair");
> +			return -1;
> +		}
> +
> +		sk = sks[0];
> +		addr.sun_family = AF_UNSPEC;
> +

We need a comment here which explains why we need this connect.

> +		if (connect(sk, &addr, sizeof(addr.sun_family))) {
> +			pr_perror("Can't clear socker peer");
> +			return -1;
> +		}
> +
> +		if (restore_sk_queue(sks[1], ui->ue->id)) {
> +			pr_perror("Can't restore socket queue");
> +			return -1;
> +		}
> +		close(sks[1]);
>  	} else {
>  		if (ui->ue->uflags & USK_CALLBACK) {
>  			sk = run_plugins(RESTORE_UNIX_SK, ui->ue->ino);
>