CONC-783 Fix potential loss of "Proxy header not accepted from host" error

Send the proxy header and handshake response in a single write.

If the client uses two separate send() calls, the server's error message
"Proxy header not accepted from host" may be lost. This occurs because
the server sends a TCP RST (reset) instead of a FIN if it closes the socket
while the client is still sending data.

As a result, the client may receive ECONNRESET or EPIPE, without seeing
the actual error from the server.

Author: vaintroub

include/mariadb_com.h

@@ -413,6 +413,7 @@ void	ma_net_end(NET *net);
 void	ma_net_clear(NET *net);
 int	ma_net_flush(NET *net);
 int	ma_net_write(NET *net,const unsigned char *packet, size_t len);
+int ma_net_write_buff(NET *net, const char *packet, size_t len);
 int	ma_net_write_command(NET *net,unsigned char command,const char *packet,
 			  size_t len, my_bool disable_flush);
 int	ma_net_real_write(NET *net,const char *packet, size_t len);

libmariadb/ma_net.c

@@ -73,7 +73,7 @@ ulong net_buffer_length= 8192;	/* Default length. Enlarged if necessary */
  ** can't normally do this the client should have a bigger max-buffer.
  */
 
-static int ma_net_write_buff(NET *net,const char *packet, size_t len);
+int ma_net_write_buff(NET *net,const char *packet, size_t len);
 
 
 /* Init with packet info */
@@ -246,7 +246,7 @@ int ma_net_write_command(NET *net, uchar command,
 }
 
 
-static int ma_net_write_buff(NET *net,const char *packet, size_t len)
+int ma_net_write_buff(NET *net,const char *packet, size_t len)
 {
   size_t left_length;
 

libmariadb/mariadb_lib.c

@@ -1783,17 +1783,6 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
     goto error;
   }
 
-  if (mysql->options.extension && mysql->options.extension->proxy_header)
-  {
-    char *hdr = mysql->options.extension->proxy_header;
-    size_t len = mysql->options.extension->proxy_header_len;
-    if (ma_pvio_write(pvio, (unsigned char *)hdr, len) <= 0)
-    {
-      ma_pvio_close(pvio);
-      goto error;
-    }
-  }
-
   if (ma_net_init(net, pvio))
   {
     ma_pvio_close(pvio);

plugins/auth/my_auth.c

@@ -208,6 +208,11 @@ static int send_client_reply_packet(MCPVIO_EXT *mpvio,
   char *buff, *end;
   size_t conn_attr_len= (mysql->options.extension) ? 
                          mysql->options.extension->connect_attrs_len : 0;
+  size_t proxy_header_len= 0;
+  char *proxy_header=
+      (mysql->options.extension) ? mysql->options.extension->proxy_header : NULL;
+  if (proxy_header)
+    proxy_header_len= mysql->options.extension->proxy_header_len;
 
   /* see end= buff+32 below, fixed size of the packet is 32 bytes */
   buff= malloc(33 + USERNAME_LENGTH + data_len + NAME_LEN + NAME_LEN + conn_attr_len + 9);
@@ -340,6 +345,9 @@ static int send_client_reply_packet(MCPVIO_EXT *mpvio,
       Send mysql->client_flag, max_packet_size - unencrypted otherwise
       the server does not know we want to do SSL
     */
+    if (proxy_header_len)
+      ma_net_write_buff(net, proxy_header, proxy_header_len);
+
     if (ma_net_write(net, (unsigned char *)buff, (size_t) (end-buff)) || ma_net_flush(net))
     {
       my_set_error(mysql, CR_SERVER_LOST, SQLSTATE_UNKNOWN,
@@ -417,6 +425,8 @@ static int send_client_reply_packet(MCPVIO_EXT *mpvio,
     *end++= compression_level;
   }
 
+  if (proxy_header_len)
+    ma_net_write_buff(net, proxy_header, proxy_header_len);
   /* Write authentication package */
   if (ma_net_write(net, (unsigned char *)buff, (size_t) (end-buff)) || ma_net_flush(net))
   {