1/* Socket timestamp conversion routines.
2 Copyright (C) 2021-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <bits/timesize.h>
20
21#if __TIMESIZE != 64
22# include <stdint.h>
23# include <string.h>
24# include <sys/socket.h>
25# include <socket-constants-time64.h>
26# include <libc-diag.h>
27
28/* It converts the first SO_TIMESTAMP or SO_TIMESTAMPNS with 32-bit time and
29 appends it to the control buffer. The 32-bit time field is kept as-is.
30
31 Calls with __TIMESIZE=32 will see the converted 64-bit time control
32 messages as spurious control message of unknown type.
33
34 Calls with __TIMESIZE=64 running on pre-time64 kernels will see the
35 original message as a spurious control ones of unknown typ while running
36 on kernel with native 64-bit time support will only see the time64 version
37 of the control message. */
38void
39__convert_scm_timestamps (struct msghdr *msg, socklen_t msgsize)
40{
41 if (msg->msg_control == NULL || msg->msg_controllen == 0)
42 return;
43
44 /* The returned control message format for SO_TIMESTAMP_NEW is a
45 'struct __kernel_sock_timeval' while for SO_TIMESTAMPNS_NEW is a
46 'struct __kernel_timespec'. In either case it is two uint64_t
47 members. */
48
49 /* GCC 6 issues an warning that tvts[0]/tvts[1] maybe be used uninitialized,
50 however it would be used if type is set to a value different than 0
51 (done by either COMPAT_SO_TIMESTAMP_OLD or COMPAT_SO_TIMESTAMPNS_OLD)
52 which will fallthrough to 'common' label. */
53 DIAG_PUSH_NEEDS_COMMENT;
54 DIAG_IGNORE_NEEDS_COMMENT (6, "-Wmaybe-uninitialized");
55 int64_t tvts[2];
56 DIAG_POP_NEEDS_COMMENT;
57 int32_t tmp[2];
58
59 struct cmsghdr *cmsg, *last = NULL;
60 int type = 0;
61
62 for (cmsg = CMSG_FIRSTHDR (msg);
63 cmsg != NULL;
64 cmsg = CMSG_NXTHDR (msg, cmsg))
65 {
66 last = cmsg;
67
68 if (cmsg->cmsg_level != SOL_SOCKET)
69 continue;
70
71 switch (cmsg->cmsg_type)
72 {
73 case COMPAT_SO_TIMESTAMP_OLD:
74 if (type != 0)
75 break;
76 type = COMPAT_SO_TIMESTAMP_NEW;
77 goto common;
78
79 case COMPAT_SO_TIMESTAMPNS_OLD:
80 type = COMPAT_SO_TIMESTAMPNS_NEW;
81
82 /* fallthrough */
83 common:
84 memcpy (tmp, CMSG_DATA (cmsg), sizeof (tmp));
85 tvts[0] = tmp[0];
86 tvts[1] = tmp[1];
87 break;
88 }
89 }
90
91 if (type == 0)
92 return;
93
94 if (CMSG_SPACE (sizeof tvts) > msgsize - msg->msg_controllen)
95 {
96 msg->msg_flags |= MSG_CTRUNC;
97 return;
98 }
99
100 /* Zero memory for the new cmsghdr, so reading cmsg_len field
101 by CMSG_NXTHDR does not trigger UB. */
102 memset (msg->msg_control + msg->msg_controllen, 0,
103 CMSG_SPACE (sizeof tvts));
104 msg->msg_controllen += CMSG_SPACE (sizeof tvts);
105 cmsg = CMSG_NXTHDR (msg, last);
106 cmsg->cmsg_level = SOL_SOCKET;
107 cmsg->cmsg_type = type;
108 cmsg->cmsg_len = CMSG_LEN (sizeof tvts);
109 memcpy (CMSG_DATA (cmsg), tvts, sizeof tvts);
110}
111#endif
112