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