include/uapi/linux/msg.h

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