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fdpassing-keith-packard
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Split out I/O functions to separate file 

Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Keith Packard 2012-10-05 11:01:47 -07:00
parent 8a0022bbb0
commit 3cea43ccbe
4 changed files with 206 additions and 108 deletions
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6
Makefile
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@ -1,4 +1,6 @@
CFLAGS=-O0 -g
fdpassing: fdpassing.o
$(CC) -o $@ fdpassing.o
all: fdpassing
fdpassing: fdpassing.o fdpass.o
$(CC) -o $@ fdpassing.o fdpass.o

116
fdpass.c Normal file
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@ -0,0 +1,116 @@
/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include "fdpass.h"
int
sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd)
{
ssize_t size;
struct msghdr msg;
struct iovec iov;
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof (int))];
} cmsgu;
struct cmsghdr *cmsg;
iov.iov_base = buf;
iov.iov_len = bufsize;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
if (fd) {
msg.msg_control = cmsgu.control;
msg.msg_controllen = sizeof(cmsgu.control);
size = recvmsg (sock, &msg, 0);
} else {
size = read (sock, buf, bufsize);
}
if (size < 0) {
perror("recvmsg");
exit(1);
}
if (fd && (cmsg = CMSG_FIRSTHDR(&msg)) &&
cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
if (cmsg->cmsg_level != SOL_SOCKET) {
fprintf (stderr, "invalid cmsg_level %d\n",
cmsg->cmsg_level);
exit(1);
}
if (cmsg->cmsg_type != SCM_RIGHTS) {
fprintf (stderr, "invalid cmsg_type %d\n",
cmsg->cmsg_type);
exit(1);
}
*fd = *((int *) CMSG_DATA(cmsg));
printf ("received fd %d\n", *fd);
} else if (fd) {
*fd = -1;
}
return size;
}
ssize_t
sock_fd_write(int sock, void *buf, ssize_t buflen, int fd)
{
ssize_t size;
struct msghdr msg;
struct iovec iov;
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof (int))];
} cmsgu;
struct cmsghdr *cmsg;
iov.iov_base = buf;
iov.iov_len = buflen;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
if (fd != -1) {
msg.msg_control = cmsgu.control;
msg.msg_controllen = sizeof(cmsgu.control);
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof (int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
printf ("passing fd %d\n", fd);
*((int *) CMSG_DATA(cmsg)) = fd;
} else {
msg.msg_control = NULL;
msg.msg_controllen = 0;
printf ("not passing fd\n");
}
size = sendmsg(sock, &msg, 0);
if (size < 0)
perror ("sendmsg");
return size;
}

35
fdpass.h Normal file
View File

@ -0,0 +1,35 @@
/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#ifndef _FDPASS_H_
#define _FDPASS_H_
#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int
sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd);
ssize_t
sock_fd_write(int sock, void *buf, ssize_t buflen, int fd);
#endif

157
fdpassing.c
View File

@ -15,129 +15,73 @@
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include "fdpass.h"
int
sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd)
char *
itoa(int i, char *buf)
{
ssize_t size;
struct msghdr msg;
struct iovec iov;
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof (int))];
} cmsgu;
struct cmsghdr *cmsg;
buf += 10;
*--buf = '\0';
do {
*--buf = '0' + i % 10;
} while ((i /= 10));
return buf;
}
iov.iov_base = buf;
iov.iov_len = bufsize;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = cmsgu.control;
msg.msg_controllen = sizeof(cmsgu.control);
size = recvmsg (sock, &msg, 0);
if (size < 0) {
perror("recvmsg");
exit(1);
}
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg &&
cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
if (cmsg->cmsg_level != SOL_SOCKET) {
fprintf (stderr, "invalid cmsg_level %d\n",
cmsg->cmsg_level);
exit(1);
}
if (cmsg->cmsg_type != SCM_RIGHTS) {
fprintf (stderr, "invalid cmsg_type %d\n",
cmsg->cmsg_type);
exit(1);
}
*fd = *((int *) CMSG_DATA(cmsg));
printf ("received fd %d\n", *fd);
} else {
*fd = -1;
}
return size;
void
handler(int i)
{
char buf[12];
char *b = itoa(i, buf);
write (2, "signal ", 7);
write (2, b, strlen(b));
write (2, "\n", 1);
_exit(1);
}
void
child(int sock)
{
int fd;
int fd, *fdp;
char buf[16];
ssize_t size;
int i = 0;
size = sock_fd_read(sock, buf, sizeof(buf), &fd);
if (size == 0)
return;
printf ("read %d\n", size);
if (fd != -1)
write(fd, "hello, world\n", 13);
}
ssize_t
sock_fd_write(int sock, void *buf, ssize_t buflen, int fd)
{
ssize_t size;
struct msghdr msg;
struct iovec iov;
union {
struct cmsghdr cmsghdr;
char control[CMSG_SPACE(sizeof (int))];
} cmsgu;
struct cmsghdr *cmsg;
iov.iov_base = buf;
iov.iov_len = buflen;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
if (fd != -1) {
msg.msg_control = cmsgu.control;
msg.msg_controllen = sizeof(cmsgu.control);
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof (int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
printf ("passing fd %d\n", fd);
*((int *) CMSG_DATA(cmsg)) = fd;
} else {
msg.msg_control = NULL;
msg.msg_controllen = 0;
printf ("not passing fd\n");
signal(SIGSEGV, handler);
sleep(1);
for (;;) {
if (!(i & 1))
fdp = NULL;
else
fdp = &fd;
size = sock_fd_read(sock, buf, sizeof(buf), fdp);
if (size == 0)
break;
printf ("read %d\n", size);
if (fdp && fd != -1)
write(fd, "hello, world\n", 13);
i++;
}
size = sendmsg(sock, &msg, 0);
if (size < 0)
perror ("sendmsg");
return size;
printf ("child done\n");
}
void
parent(int sock)
{
ssize_t size;
size = sock_fd_write(sock, "1", 1, 1);
int i;
int fd;
printf ("wrote %d\n", size);
for (i = 0; i < 8; i++) {
if ((i & 1))
fd = -1;
else
fd = 1;
size = sock_fd_write(sock, "1", 1, fd);
printf ("wrote %d\n", size);
}
close(sock);
}
int
@ -152,15 +96,16 @@ main(int argc, char **argv)
}
switch ((pid = fork())) {
case 0:
close(sv[0]);
child(sv[1]);
break;
case -1:
perror("fork");
exit(1);
default:
close(sv[1]);
parent(sv[0]);
sleep(1);
kill(pid, SIGTERM);
break;
}
return 0;
}