pipes/fifo_seqnum.h

This is pipes/fifo_seqnum.h (Listing 44-6, page 911), an example from the book, The Linux Programming Interface.

The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

  Cover of The Linux Programming Interface
+/* fifo_seqnum.h
+
+   Header file used by fifo_seqnum_server.c and fifo_seqnum_client.c
+
+   These programs create FIFOS in /tmp. This makes it easy to compile and
+   run the programs. However, for a security reasons, a real-world
+   application should never create sensitive files in /tmp. (As a simple of
+   example of the kind of security problems that can result, a malicious
+   user could create a FIFO using the name defined in SERVER_FIFO, and
+   thereby cause a denial of service attack against this application.
+   See Section 38.7 of "The Linux Programming Interface" for more details
+   on this subject.)
+*/
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include "tlpi_hdr.h"
 
 #define SERVER_FIFO "/tmp/seqnum_sv"
                                 /* Well-known name for server's FIFO */
 #define CLIENT_FIFO_TEMPLATE "/tmp/seqnum_cl.%ld"
                                 /* Template for building client FIFO name */
 #define CLIENT_FIFO_NAME_LEN (sizeof(CLIENT_FIFO_TEMPLATE) + 20)
                                 /* Space required for client FIFO pathname
                                   (+20 as a generous allowance for the PID) */
 
 struct request {                /* Request (client --> server) */
     pid_t pid;                  /* PID of client */
     int seqLen;                 /* Length of desired sequence */
 };
 
 struct response {               /* Response (server --> client) */
     int seqNum;                 /* Start of sequence */
 };

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