Re: [PATCH V7 28/29] chardev: cpr for sockets

[Steven Sistare]

On 2/18/2022 4:03 AM, Guoyi Tu wrote:
> On Wed, 2021-12-22 at 11:05 -0800, Steve Sistare wrote:
>> Save accepted socket fds before cpr-save, and look for them after
>> cpr-load.
>> in the environment after cpr-load.  Reject cpr-exec if a socket
>> enables
>> the TLS or websocket option.  Allow a monitor socket by closing it on
>> exec.
>>
>> Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>>  chardev/char-socket.c | 35 +++++++++++++++++++++++++++++++++++
>>  monitor/hmp.c         |  3 +++
>>  monitor/qmp.c         |  3 +++
>>  3 files changed, 41 insertions(+)
>>
>> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
>> index d619088..c111e17 100644
>> --- a/chardev/char-socket.c
>> +++ b/chardev/char-socket.c
>> @@ -26,6 +26,7 @@
>>  #include "chardev/char.h"
>>  #include "io/channel-socket.h"
>>  #include "io/channel-websock.h"
>> +#include "migration/cpr.h"
>>  #include "qemu/error-report.h"
>>  #include "qemu/module.h"
>>  #include "qemu/option.h"
>> @@ -358,6 +359,10 @@ static void tcp_chr_free_connection(Chardev
>> *chr)
>>      SocketChardev *s = SOCKET_CHARDEV(chr);
>>      int i;
>>  
>> +    if (!chr->reopen_on_cpr) {
>> +        cpr_delete_fd(chr->label, 0);
>> +    }
>> +
>>      if (s->read_msgfds_num) {
>>          for (i = 0; i < s->read_msgfds_num; i++) {
>>              close(s->read_msgfds[i]);
>> @@ -920,6 +925,10 @@ static void tcp_chr_accept(QIONetListener
>> *listener,
>>                                 QIO_CHANNEL(cioc));
>>      }
>>      tcp_chr_new_client(chr, cioc);
>> +
>> +    if (s->sioc && !chr->reopen_on_cpr) {
> 
> Is it necessary check if the device has QEMU_CHAR_FEATURE_CPR feature
> here? In my opinion, fd should not be saved if device don't support
> cpr.

OK.  I'll add a new boolean member to CharDev that controls whether or not
to use cpr fd's:

    qemu_char_open()
        chr->cpr_enabled = (!chr->reopen_on_cpr && 
                            qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_CPR));

    tcp_chr_accept()
        if (s->sioc && chr->cpr_enabled) {
            cpr_save_fd(chr->label, 0, s->sioc->fd);
        }

... and test it at other places as well.

- Steve

>> +        cpr_save_fd(chr->label, 0, s->sioc->fd);
>> +    }
>>  }
>>  
>>  
>> @@ -1175,6 +1184,26 @@ static gboolean
>> socket_reconnect_timeout(gpointer opaque)
>>      return false;
>>  }
>>  
>> +static int load_char_socket_fd(Chardev *chr, Error **errp)
>> +{
>> +    SocketChardev *sockchar = SOCKET_CHARDEV(chr);
>> +    QIOChannelSocket *sioc;
>> +    const char *label = chr->label;
>> +    int fd = cpr_find_fd(label, 0);
>> +
>> +    if (fd != -1) {
>> +        sockchar = SOCKET_CHARDEV(chr);
>> +        sioc = qio_channel_socket_new_fd(fd, errp);
>> +        if (sioc) {
>> +            tcp_chr_accept(sockchar->listener, sioc, chr);
>> +            object_unref(OBJECT(sioc));
>> +        } else {
>> +            error_setg(errp, "could not restore socket for %s",
>> label);
>> +            return -1;
>> +        }
>> +    }
>> +    return 0;
>> +}
>>  
>>  static int qmp_chardev_open_socket_server(Chardev *chr,
>>                                            bool is_telnet,
>> @@ -1385,6 +1414,10 @@ static void qmp_chardev_open_socket(Chardev
>> *chr,
>>      }
>>      s->registered_yank = true;
>>  
>> +    if (!s->tls_creds && !s->is_websock) {
>> +        qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_CPR);
>> +    }
>> +
>>      /* be isn't opened until we get a connection */
>>      *be_opened = false;
>>  
>> @@ -1400,6 +1433,8 @@ static void qmp_chardev_open_socket(Chardev
>> *chr,
>>              return;
>>          }
>>      }
>> +
>> +    load_char_socket_fd(chr, errp);
>>  }
>>  
>>  static void qemu_chr_parse_socket(QemuOpts *opts, ChardevBackend
>> *backend,