LXR linux/include/uapi/linux/msg.h

   1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2#ifndef _UAPI_LINUX_MSG_H
   3#define _UAPI_LINUX_MSG_H
   4
   5#include <linux/ipc.h>
   6
   7/* ipcs ctl commands */
   8#define MSG_STAT 11
   9#define MSG_INFO 12
  10#define MSG_STAT_ANY 13
  11
  12/* msgrcv options */
  13#define MSG_NOERROR     010000  /* no error if message is too big */
  14#define MSG_EXCEPT      020000  /* recv any msg except of specified type.*/
  15#define MSG_COPY        040000  /* copy (not remove) all queue messages */
  16
  17/* Obsolete, used only for backwards compatibility and libc5 compiles */
  18struct msqid_ds {
  19        struct ipc_perm msg_perm;
  20        struct msg *msg_first;          /* first message on queue,unused  */
  21        struct msg *msg_last;           /* last message in queue,unused */
  22        __kernel_old_time_t msg_stime;  /* last msgsnd time */
  23        __kernel_old_time_t msg_rtime;  /* last msgrcv time */
  24        __kernel_old_time_t msg_ctime;  /* last change time */
  25        unsigned long  msg_lcbytes;     /* Reuse junk fields for 32 bit */
  26        unsigned long  msg_lqbytes;     /* ditto */
  27        unsigned short msg_cbytes;      /* current number of bytes on queue */
  28        unsigned short msg_qnum;        /* number of messages in queue */
  29        unsigned short msg_qbytes;      /* max number of bytes on queue */
  30        __kernel_ipc_pid_t msg_lspid;   /* pid of last msgsnd */
  31        __kernel_ipc_pid_t msg_lrpid;   /* last receive pid */
  32};
  33
  34/* Include the definition of msqid64_ds */
  35#include <asm/msgbuf.h>
  36
  37/* message buffer for msgsnd and msgrcv calls */
  38struct msgbuf {
  39        __kernel_long_t mtype;          /* type of message */
  40        char mtext[1];                  /* message text */
  41};
  42
  43/* buffer for msgctl calls IPC_INFO, MSG_INFO */
  44struct msginfo {
  45        int msgpool;
  46        int msgmap; 
  47        int msgmax; 
  48        int msgmnb; 
  49        int msgmni; 
  50        int msgssz; 
  51        int msgtql; 
  52        unsigned short  msgseg; 
  53};
  54
  55/*
  56 * MSGMNI, MSGMAX and MSGMNB are default values which can be
  57 * modified by sysctl.
  58 *
  59 * MSGMNI is the upper limit for the number of messages queues per
  60 * namespace.
  61 * It has been chosen to be as large possible without facilitating
  62 * scenarios where userspace causes overflows when adjusting the limits via
  63 * operations of the form retrieve current limit; add X; update limit".
  64 *
  65 * MSGMNB is the default size of a new message queue. Non-root tasks can
  66 * decrease the size with msgctl(IPC_SET), root tasks
  67 * (actually: CAP_SYS_RESOURCE) can both increase and decrease the queue
  68 * size. The optimal value is application dependent.
  69 * 16384 is used because it was always used (since 0.99.10)
  70 *
  71 * MAXMAX is the maximum size of an individual message, it's a global
  72 * (per-namespace) limit that applies for all message queues.
  73 * It's set to 1/2 of MSGMNB, to ensure that at least two messages fit into
  74 * the queue. This is also an arbitrary choice (since 2.6.0).
  75 */
  76
  77#define MSGMNI 32000   /* <= IPCMNI */     /* max # of msg queue identifiers */
  78#define MSGMAX  8192   /* <= INT_MAX */   /* max size of message (bytes) */
  79#define MSGMNB 16384   /* <= INT_MAX */   /* default max size of a message queue */
  80
  81/* unused */
  82#define MSGPOOL (MSGMNI * MSGMNB / 1024) /* size in kbytes of message pool */
  83#define MSGTQL  MSGMNB            /* number of system message headers */
  84#define MSGMAP  MSGMNB            /* number of entries in message map */
  85#define MSGSSZ  16                /* message segment size */
  86#define __MSGSEG ((MSGPOOL * 1024) / MSGSSZ) /* max no. of segments */
  87#define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
  88
  89
  90#endif /* _UAPI_LINUX_MSG_H */
  91