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


From: Amos Kong
Subject: Re: [Qemu-devel] [PATCH v3 1/9] net: introduce tcp_server_start()
Date: Wed, 14 Mar 2012 16:33:14 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1

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<address@hidden>
---
  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.



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