/usr/include/linux/msg.h is in linux-libc-dev 4.9.144-3.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 | #ifndef _LINUX_MSG_H
#define _LINUX_MSG_H
#include <linux/ipc.h>
/* ipcs ctl commands */
#define MSG_STAT 11
#define MSG_INFO 12
/* msgrcv options */
#define MSG_NOERROR 010000 /* no error if message is too big */
#define MSG_EXCEPT 020000 /* recv any msg except of specified type.*/
#define MSG_COPY 040000 /* copy (not remove) all queue messages */
/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct msqid_ds {
struct ipc_perm msg_perm;
struct msg *msg_first; /* first message on queue,unused */
struct msg *msg_last; /* last message in queue,unused */
__kernel_time_t msg_stime; /* last msgsnd time */
__kernel_time_t msg_rtime; /* last msgrcv time */
__kernel_time_t msg_ctime; /* last change time */
unsigned long msg_lcbytes; /* Reuse junk fields for 32 bit */
unsigned long msg_lqbytes; /* ditto */
unsigned short msg_cbytes; /* current number of bytes on queue */
unsigned short msg_qnum; /* number of messages in queue */
unsigned short msg_qbytes; /* max number of bytes on queue */
__kernel_ipc_pid_t msg_lspid; /* pid of last msgsnd */
__kernel_ipc_pid_t msg_lrpid; /* last receive pid */
};
/* Include the definition of msqid64_ds */
#include <asm/msgbuf.h>
/* message buffer for msgsnd and msgrcv calls */
struct msgbuf {
__kernel_long_t mtype; /* type of message */
char mtext[1]; /* message text */
};
/* buffer for msgctl calls IPC_INFO, MSG_INFO */
struct msginfo {
int msgpool;
int msgmap;
int msgmax;
int msgmnb;
int msgmni;
int msgssz;
int msgtql;
unsigned short msgseg;
};
/*
* MSGMNI, MSGMAX and MSGMNB are default values which can be
* modified by sysctl.
*
* MSGMNI is the upper limit for the number of messages queues per
* namespace.
* It has been chosen to be as large possible without facilitating
* scenarios where userspace causes overflows when adjusting the limits via
* operations of the form retrieve current limit; add X; update limit".
*
* MSGMNB is the default size of a new message queue. Non-root tasks can
* decrease the size with msgctl(IPC_SET), root tasks
* (actually: CAP_SYS_RESOURCE) can both increase and decrease the queue
* size. The optimal value is application dependent.
* 16384 is used because it was always used (since 0.99.10)
*
* MAXMAX is the maximum size of an individual message, it's a global
* (per-namespace) limit that applies for all message queues.
* It's set to 1/2 of MSGMNB, to ensure that at least two messages fit into
* the queue. This is also an arbitrary choice (since 2.6.0).
*/
#define MSGMNI 32000 /* <= IPCMNI */ /* max # of msg queue identifiers */
#define MSGMAX 8192 /* <= INT_MAX */ /* max size of message (bytes) */
#define MSGMNB 16384 /* <= INT_MAX */ /* default max size of a message queue */
/* unused */
#define MSGPOOL (MSGMNI * MSGMNB / 1024) /* size in kbytes of message pool */
#define MSGTQL MSGMNB /* number of system message headers */
#define MSGMAP MSGMNB /* number of entries in message map */
#define MSGSSZ 16 /* message segment size */
#define __MSGSEG ((MSGPOOL * 1024) / MSGSSZ) /* max no. of segments */
#define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
#endif /* _LINUX_MSG_H */
|