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/*************************************************************************\
* Copyright (C) Michael Kerrisk, 2018. *
* *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the *
* Free Software Foundation, either version 3 or (at your option) any *
* later version. This program is distributed without any warranty. See *
* the file COPYING.gpl-v3 for details. *
\*************************************************************************/
/* is_seqnum_v3_sv.c (KB)
A simple Internet stream socket server. Our service is to provide unique
sequence numbers to the client.
This program is the same as is_seqnum_v2.c, except that it forks a
subprocess to do the work, and it sends the connection fd to the
child over an AF_UNIX socket. Invoke it with --debug to allow time
to attach gdb to the child. (KB)
Usage: is_seqnum_sv [init-seq-num] (default = 0)
See also is_seqnum_v2_cl.c.
*/
#include "af_unix_hdr.h"
#include "is_seqnum_v2.h"
int
main(int argc, char *argv[])
{
uint32_t seqNum;
char reqLenStr[INT_LEN]; /* Length of requested sequence */
char seqNumStr[INT_LEN]; /* Start of granted sequence */
struct sockaddr *claddr;
int lfd, reqLen;
socklen_t addrlen, alen;
char addrStr[IS_ADDR_STR_LEN];
Boolean debug = FALSE;
pid_t pid;
int pipefd[2];
int pfd; /* parent's end */
int cfd; /* child's end */
if (argc > 1 && strcmp (argv[1], "--help") == 0)
usageErr ("%s [--debug] [init-seq-num]\n", argv[0]);
if (argc > 1 && strcmp (argv[1], "--debug") == 0)
debug = TRUE;
if (!debug)
seqNum = (argc > 1) ? getInt (argv[1], 0, "init-seq-num") : 0;
else
seqNum = (argc > 2) ? getInt (argv[2], 0, "init-seq-num") : 0;
/* Ignore the SIGPIPE signal, so that we find out about broken connection
errors via a failure from write(). */
if (signal (SIGPIPE, SIG_IGN) == SIG_ERR)
errExit("signal");
lfd = inetListen (PORT_NUM_STR, 5, &addrlen);
if (lfd == -1)
fatal ("inetListen() failed");
/* Allocate a buffer large enough to hold the client's socket address */
claddr = malloc (addrlen);
if (claddr == NULL)
errExit ("malloc");
/* Fork a child to handle client request. */
if (socketpair (AF_UNIX, SOCK_STREAM, 0, pipefd) < 0)
errExit ("socketpair");
pfd = pipefd[1];
cfd = pipefd[0];
if ((pid = fork ()) < 0)
errExit ("fork");
else if (pid > 0) /* parent */
{
int connfd, junk;
if (close (cfd) < 0)
errExit ("close");
if (debug)
{
printf ("parent pid %d, child pid %d, sleeping...\n", getpid (), pid);
sleep (30);
}
/* Accept a client connection, obtaining client's address */
alen = addrlen;
connfd = accept (lfd, (struct sockaddr *) claddr, &alen);
if (connfd == -1)
errExit ("accept");
printf ("Connection from %s\n", inetAddressStr (claddr, alen, addrStr,
IS_ADDR_STR_LEN));
printf ("Sending fd %d to child\n", connfd);
if (sendfd (pfd, connfd) < 0)
errExit ("sendfd");
if (close (connfd) < 0)
errExit ("close");
/* Wait for child. */
if (read (pfd, &junk, sizeof junk) != sizeof junk)
errMsg ("read");
if (close (pfd) < 0)
errMsg ("close");
if (close (lfd) < 0)
errExit ("close");
}
else /* child */
{
int connfd, junk;
if (close (pfd) < 0)
errExit ("close");
if (close (lfd) < 0)
errExit ("close");
if (debug)
sleep (30);
/* Get connection fd from parent. */
connfd = recvfd (cfd);
if (connfd < 0)
errExit ("recvfd");
/* Read client request, send sequence number back */
if (readLine (connfd, reqLenStr, INT_LEN) <= 0)
{
close (connfd);
errExit ("readLine");
}
reqLen = atoi (reqLenStr);
if (reqLen <= 0)
{
close(cfd);
errExit ("Bad request");
}
snprintf (seqNumStr, INT_LEN, "%d\n", seqNum);
if (write (connfd, seqNumStr, strlen (seqNumStr)) != strlen(seqNumStr))
errExit ("write");
seqNum += reqLen; /* Update sequence number */
if (close (connfd) == -1) /* Close connection */
errMsg ("close");
/* Tell parent we're done. */
if (write (cfd, &junk, sizeof junk) != sizeof junk)
errMsg ("write");
if (close (cfd) < 0)
errExit ("close");
}
}
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