1 /***************************************************************************
2  * Copyright (c) 2024 Microsoft Corporation
3  *
4  * This program and the accompanying materials are made available under the
5  * terms of the MIT License which is available at
6  * https://opensource.org/licenses/MIT.
7  *
8  * SPDX-License-Identifier: MIT
9  **************************************************************************/
10 
11 
12 /**************************************************************************/
13 /**************************************************************************/
14 /**                                                                       */
15 /** NetX Component                                                        */
16 /**                                                                       */
17 /**   Transmission Control Protocol (TCP)                                 */
18 /**                                                                       */
19 /**************************************************************************/
20 /**************************************************************************/
21 
22 #define NX_SOURCE_CODE
23 
24 
25 /* Include necessary system files.  */
26 
27 #include "nx_api.h"
28 #include "nx_ip.h"
29 #include "nx_tcp.h"
30 #include "nx_ipv6.h"
31 
32 
33 /**************************************************************************/
34 /*                                                                        */
35 /*  FUNCTION                                               RELEASE        */
36 /*                                                                        */
37 /*    _nx_tcp_socket_mss_set                              PORTABLE C      */
38 /*                                                           6.1          */
39 /*  AUTHOR                                                                */
40 /*                                                                        */
41 /*    Yuxin Zhou, Microsoft Corporation                                   */
42 /*                                                                        */
43 /*  DESCRIPTION                                                           */
44 /*                                                                        */
45 /*    This function sets the TCP Maximum Segment Size (MSS) for the       */
46 /*    specified TCP socket.                                               */
47 /*                                                                        */
48 /*  INPUT                                                                 */
49 /*                                                                        */
50 /*    socket_ptr                            Pointer to the TCP socket     */
51 /*    mss                                   New value for the MSS         */
52 /*                                                                        */
53 /*  OUTPUT                                                                */
54 /*                                                                        */
55 /*    status                                Completion status             */
56 /*                                                                        */
57 /*  CALLS                                                                 */
58 /*                                                                        */
59 /*    tx_mutex_get                          Obtain protection             */
60 /*    tx_mutex_put                          Release protection            */
61 /*                                                                        */
62 /*  CALLED BY                                                             */
63 /*                                                                        */
64 /*    Application Code                                                    */
65 /*                                                                        */
66 /*  RELEASE HISTORY                                                       */
67 /*                                                                        */
68 /*    DATE              NAME                      DESCRIPTION             */
69 /*                                                                        */
70 /*  05-19-2020     Yuxin Zhou               Initial Version 6.0           */
71 /*  09-30-2020     Yuxin Zhou               Modified comment(s),          */
72 /*                                            resulting in version 6.1    */
73 /*                                                                        */
74 /**************************************************************************/
_nx_tcp_socket_mss_set(NX_TCP_SOCKET * socket_ptr,ULONG mss)75 UINT  _nx_tcp_socket_mss_set(NX_TCP_SOCKET *socket_ptr, ULONG mss)
76 {
77 
78 NX_IP *ip_ptr;
79 UINT status;
80 
81     /* Setup IP pointer.  */
82     ip_ptr =  socket_ptr -> nx_tcp_socket_ip_ptr;
83 
84     if (mss == 0)
85     {
86 
87         /* Invalid MSS, return an error.  */
88         return(NX_SIZE_ERROR);
89     }
90 
91     /* Obtain the IP mutex so we can examine the bound port.  */
92     tx_mutex_get(&(ip_ptr -> nx_ip_protection), TX_WAIT_FOREVER);
93 
94     if (socket_ptr -> nx_tcp_socket_state < NX_TCP_SYN_SENT)
95     {
96 
97         /* Set the socket's MSS value.  */
98         socket_ptr -> nx_tcp_socket_mss =  mss;
99         status = NX_SUCCESS;
100     }
101     else
102     {
103 
104         /* MSS can not be modified when connection is started. */
105         status = NX_NOT_SUCCESSFUL;
106     }
107 
108     /* Release protection.  */
109     tx_mutex_put(&(ip_ptr -> nx_ip_protection));
110 
111     /* Return successful completion status.  */
112     return(status);
113 }
114 
115