IPC: Inter-process communication

Ipc:interprocesscommunication inter-process communication.

The persistence of IPC objects:

Ongoing with process: pipelines, mutexes, condition variables, read and write locks, fcntl record lockout, sockets, POSIX memory-based semaphores

Persistent with the kernel: Message Queuing, semaphores (POSIX-known semaphores and System V semaphores), shared memory

In the CS architecture, the iterative server may have a denial-of-service attack (DoS), so be aware of how long it may be blocked and blocked.

Ways to resolve Dos attacks:

1. The blocking setting time-out in the iteration server.

2. Use a parallel server.

The best solution to producer consumer problems is the IPC, which avoids the creation of deadlocks;

Producers put data in buffers and consumers use that data.

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3 Technologies of IPC:

6 interfaces for passing messages between processes (threads):

1. Piping

2. Message Queuing

3. Procedure Call

6 types of interfaces that are synchronized between processes (threads):

1. Signal volume (two kinds)

2. Mutex Amount

3. Condition variables

4. Read/write Lock

5. Record lock

2 interfaces for shared memory between processes (threads):

1. Anonymous shared memory

2. Well-known shared memory

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POSIX IPC:

POSIX semaphore:

-lpthread

#include <semaphore.h>

POSIX Message Queuing:

-lrt

#include <mqueue.h>

POSIX shared memory

-lrt

#include <sys/mman.h>

The POSIX IPC functions are library functions and include header files:

#include <fcntl.h>

#include <sys/stat.h>

To create or open an IPC parameter using the appropriate open function:

Name

The name of the IPC, which is the name of thePOSIX IPC in Linux, begins with/ .

Oflags:

O_rdonly: Read-only, not available for semaphores

O_wronly: Write only, only for Message Queuing

O_RDWR: Read and write, cannot be used for semaphores

O_creat: Created if not present, exists to return existing

O_EXCL: Non-sexual creation

O_nonblock: Non-blocking IO, only for Message Queuing

O_trunc: Short cut if present, only for shared memory

Whenoflags=o_creat mode: Specify the permission bit

S_irusr

S_iwusr

S_ixusr

S_irgrp

S_iwgrp

S_ixgrp

S_iroth

S_iwoth

S_ixoth

The above rules apply only to Message Queuing and semaphores, and the shared memory mode must be specified, if no o_creat is specified, then the mode=0 of the shared memory.

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System V IPC:

System V Signal Volume

#include <sys/sem.h>

System V Message Queuing

#include <sys/msg.h>

System V Shared memory

#include <sys/shm.h>

The IPC functions of System V are both systems calls and files that contain headers:

#include <sys/ipc.h>

#include <sys/types.h>

Use the appropriate get function to create or open IPC using key_t as their name.

The Ftok function converts an existing path and an integer identifier into a key_t value, called the IPC key.

#include <sys/types.h>

#include <sys/ipc.h>

key_t ftok(const char *pathname, int proj_id);

So the name of the IPC for System V is a file,

The IPC name of System V in Linux requires the file to be created in advance to be converted using Ftok.

The kernel maintains an information structure for each IPC object:

struct IPC_PERM

{

IPC Key:

key_t __key;

Owner ID:

uid_t uid;

gid_t GID;

Creator ID:

uid_t cuid;

gid_t Cgid;

Permissions:

unsigned short mode;

unsigned short __seq;

};

View and DELETE commands for the IPC of System V:

IPCS: View IPC for System V

-M: Shared memory

-Q: Message Queuing

-S: Signal volume

IPCRM: Remove IPC for System V

IPC: Inter-process communication