Re: [Qemu-devel] [PATCH v3 1/9] net: introduce tcp_server_start()

[Amos Kong <akong@redhat.com>]

On 14/03/12 00:39, Michael Roth wrote:
> On Wed, Mar 07, 2012 at 06:47:45AM +0800, Amos Kong wrote:
>> Introduce tcp_server_start() by moving original code in
>> tcp_start_incoming_migration().
>>
>> Signed-off-by: Amos Kong<akong@redhat.com>
>> ---
>>   net.c         |   28 ++++++++++++++++++++++++++++
>>   qemu_socket.h |    2 ++
>>   2 files changed, 30 insertions(+), 0 deletions(-)
>>
>> diff --git a/net.c b/net.c
>> index c34474f..e90ff23 100644
>> --- a/net.c
>> +++ b/net.c
>> @@ -99,6 +99,34 @@ static int get_str_sep(char *buf, int buf_size, const char **pp, int sep)
>>       return 0;
>>   }
>>
>> +int tcp_server_start(const char *str, int *fd)
>> +{
>> +    int val, ret;
>> +    struct sockaddr_in saddr;
>> +
>> +    if (parse_host_port(&saddr, str)<  0) {
>> +        error_report("invalid host/port combination: %s", str);
>> +        return -EINVAL;
>> +    }
>> +
>> +    *fd = qemu_socket(PF_INET, SOCK_STREAM, 0);
>> +    if (fd<  0) {
>> +        perror("socket");
>> +        return -1;
>> +    }
>> +    socket_set_nonblock(*fd);
>> +
>> +    /* allow fast reuse */
>> +    val = 1;
>> +    setsockopt(*fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&val, sizeof(val));
>> +
>> +    ret = bind(*fd, (struct sockaddr *)&saddr, sizeof(saddr));
>> +    if (ret<  0) {
>> +        closesocket(*fd);
>> +    }
>> +    return ret;
>> +}
>> +
>
> I would combine this with patch 2, since it provides context for why
> this function is being added. Would also do the same for 3 and 4.
>
> I see client the client implementation you need to pass fd back by
> reference since ret can be set to EINPROGRESS/EWOULDBLOCK on success,

ret restores 0 or -socket_error()
  success: 0, -EINPROGRESS
  fail   : ret < 0 && ret !=-EINTR && ret != -EWOULDBLOCK

, it should be -EINPROGRESS

+        ret = connect(*fd, (struct sockaddr *)&saddr, sizeof(saddr));
+        if (ret < 0) {
+            ret = -socket_error();
+            if (ret == -EINPROGRESS) {
+                break;


> but here it looks like fd is only value if ret=0, so might as well just
> pass back the fd as the function return value.

Passed *fd tells us if socket creation success
'ret' would return 0 or -socket_error()

-socket_error() is the error of socket creation/connection, it would be 
used by other functions.

eg: migration-tcp.c:
int tcp_start_incoming_migration(
     ...
     ret = tcp_server_start(host_port, &s);
     if (ret < 0) {
         fprintf(stderr, "tcp_server_start: %s\n", strerror(-ret));

We can also add a error msg in tcp_start_outgoing_migration() when 
tcp_client_start() fails.

> Also, is there any reason we can't re-use
> qemu-sockets.c:inet_listen()/qemu-sockets.c:inet_connect()? AFAICT they
> serve the same purpose, and already include some of the work from your
> PATCH #6.

We could not directly use it, there are some difference,
such as tcp_start_incoming_migration() doesn't set socket no-blocked,
but net_socket_listen_init() sets socket no-blocked.

There are some repeated code, so I write a tcp_common_start(), and use 
it in net_socket_listen_init()/
net_socket_connect_init() and tcp_start_incoming_migration()/ 
tcp_start_outgoing_migration()


>>   int parse_host_port(struct sockaddr_in *saddr, const char *str)
>>   {
>>       char buf[512];
>> diff --git a/qemu_socket.h b/qemu_socket.h
>> index fe4cf6c..d612793 100644
>> --- a/qemu_socket.h
>> +++ b/qemu_socket.h
>> @@ -54,6 +54,8 @@ int unix_listen(const char *path, char *ostr, int olen);
>>   int unix_connect_opts(QemuOpts *opts);
>>   int unix_connect(const char *path);
>>
>> +int tcp_server_start(const char *str, int *fd);
>> +
>>   /* Old, ipv4 only bits.  Don't use for new code. */
>>   int parse_host_port(struct sockaddr_in *saddr, const char *str);
>>   int socket_init(void);
>>
>>
>

-- 
			Amos.