msg.h (3385B) - Raw
1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 2 #ifndef _LINUX_MSG_H 3 #define _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 */ 18 struct 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 */ 38 struct 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 */ 44 struct 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 /* _LINUX_MSG_H */